Move version compatibility to the consumer; name libdpm-core explicitly
dpm_require no longer takes a minimum version and applies no version criterion of its own. A handle now means the module is valid, not that it suits the caller. dpm_module_info_of is added alongside it, reporting the name, version, description, and minimum-libdpm-core version read at load, so a consuming module can judge a dependency's version for itself. The one rule still enforced is the minimum-version handshake, where libdpm-core is the host and refuses a module that demands a newer library than the one running. dpm_module_info_of joins the version script, so the exported surface is now fourteen symbols under DPM_CORE_1.0. Separately, the bare word "core" is gone from prose everywhere. It named both the command-line tool and the library, so every use forced the reader to guess which. Text now says "the dpm binary" or "libdpm-core". Identifiers keep their spelling: libdpm-core, core.h, core.conf, the "core" configuration namespace, dpm_core_version, core_min, DPM_CORE_1.0, the dpmcore namespace, test_core, core_api. Three user-visible strings changed with it: the load-refusal message now reads "requires libdpm-core >= X, running libdpm-core is Y — update libdpm-core", and the info module's description and help text name the library. The test asserting on the refusal text was updated to match. DESIGN.md's terminology line no longer defines "DPM Core" as the CLI, which was the source of the ambiguity. OVERVIEW.md is restructured around the three layers a reader meets DPM at — user, developer, filesystem — so a code-level symbol never appears without saying whose layer it is. MODULES.md describes the bundled info module as testing and demonstrating full DPM system functionality rather than as a reference implementation. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
@@ -1,4 +1,4 @@
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# Building DPM Core
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# Building libdpm-core and the dpm binary
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## Prerequisites
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@@ -21,11 +21,11 @@ Artifacts land in:
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```
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<build-dir>/bin/dpm the CLI
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<build-dir>/lib/libdpm-core.so the core library
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<build-dir>/lib/libdpm-core.so the library
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<build-dir>/modules/info.so the bundled info module
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```
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The dpm binary built here finds the locally built libdpm-core.so on its own — an embedded library search path points it at the lib/ directory next to it in the build tree, so running it directly uses the core you just built with nothing to set up first. This is only the default: LD_LIBRARY_PATH takes precedence over the embedded path, so the binary can be pointed at any other core, including the system-installed one.
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The dpm binary built here finds the locally built libdpm-core.so on its own — an embedded library search path points it at the lib/ directory next to it in the build tree, so running it directly uses the library you just built with nothing to set up first. This is only the default: LD_LIBRARY_PATH takes precedence over the embedded path, so the binary can be pointed at any other libdpm-core, including the system-installed one.
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### Running the tests
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@@ -33,7 +33,7 @@ The dpm binary built here finds the locally built libdpm-core.so on its own —
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ctest --test-dir <build-dir> --output-on-failure
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```
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This runs the core API test binary (which exercises the full load-time validation matrix against the fixture modules in tests/fixtures/) and the CLI end-to-end tests.
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This runs the API test binary (which exercises the full load-time validation matrix against the fixture modules in tests/fixtures/) and the CLI end-to-end tests.
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### Running the CLI from the build tree
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@@ -60,11 +60,11 @@ This is the packaging flow: configure once, build once, test what was built, ins
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```
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bin/dpm the CLI
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lib/libdpm-core.so the core library
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lib/libdpm-core.so the library
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lib/dpm/modules/info.so the bundled info module
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include/dpm/ the public header
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```
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Core configuration installs to /etc/dpm/conf.d/core.conf regardless of prefix.
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The libdpm-core configuration installs to /etc/dpm/conf.d/core.conf regardless of prefix.
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@@ -4,7 +4,7 @@ Programs link libdpm-core to operate the package manager directly: build systems
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## Compiling and linking
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With core installed, include the public header and link the library:
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With libdpm-core installed, include the public header and link the library:
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```
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#include <dpm/core.h>
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@@ -44,13 +44,22 @@ The root override is what makes chroot builds, image assembly, and sysroot manag
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## Acquiring and using modules
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**dpm_require** loads a module by name, on demand, with an optional minimum version:
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**dpm_require** loads a module by name, on demand:
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```
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dpm_module* mod = dpm_require(ctx, "mymodule", "1.0.0");
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dpm_module* mod = dpm_require(ctx, "mymodule");
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```
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Core validates the module completely at load; a handle is returned only for a fully valid module. NULL means the module is absent, invalid, or below the minimum — dpm_last_error(ctx) carries the precise reason. Modules load at most once per context; repeated calls return the same handle.
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libdpm-core validates the module completely at load; a handle is returned only for a fully valid module. NULL means the module is absent or invalid — dpm_last_error(ctx) carries the precise reason. Modules load at most once per context; repeated calls return the same handle.
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**dpm_module_info_of** reports what libdpm-core saw in the loaded module:
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```
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dpm_module_info info;
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dpm_module_info_of(ctx, mod, &info); /* info.name, .version, .description, .core_min */
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```
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Deciding whether that version is too new or too old is yours. libdpm-core applies no version criterion of its own — a handle means the module is valid, not that it suits you.
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**dpm_execute** drives a module the way the CLI does — a command name and arguments:
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@@ -81,7 +90,8 @@ The cursor covers every valid module in the module path; invalid candidates are
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## Services
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- **dpm_core_version()** — core's version; callable without a context.
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- **dpm_core_version()** — the libdpm-core version; callable without a context.
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- **dpm_module_info_of(ctx, mod, out)** — the name, version, description, and minimum-libdpm-core version read from a loaded module.
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- **dpm_config_get(ctx, module, section, key)** — a value from a module's configuration namespace, or NULL if unset.
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- **dpm_log(ctx, level, message)** — writes to the context's configured log targets; levels are DPM_LOG_FATAL through DPM_LOG_DEBUG.
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- **dpm_module_path(ctx)** — the resolved module directory.
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@@ -104,7 +114,7 @@ int main(void) {
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return 1;
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}
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dpm_module* mod = dpm_require(ctx, "info", NULL);
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dpm_module* mod = dpm_require(ctx, "info");
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if (!mod) {
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fprintf(stderr, "%s\n", dpm_last_error(ctx));
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dpm_close(ctx);
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114
docs/DESIGN.md
114
docs/DESIGN.md
@@ -14,7 +14,7 @@
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v v
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libdpm-core.so
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(discovery, validation, routing,
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version negotiation, config, logging)
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version reporting, config, logging)
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| |
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v v
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raw module pkg module ... future modules (repo, source, ...)
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@@ -25,52 +25,55 @@
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(source of truth) (derived cache)
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```
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libdpm-core.so is the single entry point for everything. Modules are shared objects that implement package functionality. All routing — core-to-module and module-to-module — passes through core. No consumer touches dlopen, dlsym, or module discovery itself.
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libdpm-core.so is the single entry point for everything. Modules are shared objects that implement package functionality. All routing — library-to-module and module-to-module — passes through libdpm-core. No consumer touches dlopen, dlsym, or module discovery itself.
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## Versioning model
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Compatibility is directional, and the module is the one that declares it:
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- **Each module reports the minimum core version it supports** (a reserved contract symbol). At load, core compares its own version against that minimum: running core is older → refuse with an explicit "core too old for this module" report; otherwise load. Core never rejects a module for being old, because core's contract evolves append-only — a newer core supports everything an older core did.
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- **Consumers state only minimums**, never maximums: require("raw", min 1.2) means "raw at 1.2 or anything newer." Module APIs evolve append-only (new table versions beside old ones), so newer is always acceptable and an update can never render a consumer's requirement unsatisfiable.
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- **Updates only add satisfiable states**: because bounds are minimums and evolution is append-only, updating core or any module preserves every previously working combination. The single possible load refusal — module requires a newer core — names its own remedy.
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- **Each module reports the minimum libdpm-core version it supports** (a reserved contract symbol). At load, the running library compares its own version against that minimum: if it is older → refuse with an explicit "libdpm-core too old for this module" report; otherwise load. A module is never rejected for being old, because the libdpm-core contract evolves append-only — a newer libdpm-core supports everything an older one did.
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- **Consuming modules judge module versions; libdpm-core does not.** libdpm-core reports the version it saw at load and draws no conclusion from it. A module that depends on another requires it by name, reads the reported version, and decides for itself whether that version is too new or too old for what it intends to call. A load is a statement that the module is valid, never that it is compatible with a particular caller.
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- **Updates only add satisfiable states**: module APIs evolve append-only (new table versions beside old ones), so a newer module still carries everything an older consumer called, and updating libdpm-core or any module preserves every previously working combination. The single possible load refusal — module requires a newer libdpm-core — names its own remedy.
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## libdpm-core.so
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Dependencies: libc, libstdc++, libdl. Never more — core must remain loadable in the barren case forever, so package logic never leaks into it. Core routes and hosts; modules implement.
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Dependencies: libc, libstdc++, libdl. Never more — libdpm-core must remain loadable in the barren case forever, so package logic never leaks into it. libdpm-core routes and hosts; modules implement.
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Core provides:
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libdpm-core provides:
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- **Discovery**: module path resolution, enumeration of installed module .so's.
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- **Validation**: the full load-time contract enforcement described below. Core is the sole authority on what a valid module is; the contract definition lives inside core as data. There is no SDK package — the interface is specified by this document and enforced by core's validator.
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- **Validation**: the full load-time contract enforcement described below. libdpm-core is the sole authority on what a valid module is; the contract definition lives inside the library as data. There is no SDK package — the interface is specified by this document and enforced by the library's validator.
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- **Routing**:
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- generic dispatch — execute a command string with arguments against a named module (what the CLI uses);
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- typed access — a consumer requests a module's API at a version and receives a C function table (what modules and external programs use).
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- **Version negotiation**: require resolves a module by name, checks the requested minimum, loads, and returns a handle, or reports precisely why it can't.
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- **Version reporting**: require resolves a module by name, loads it, and returns a handle, or reports precisely why it can't. The loaded module's version is readable from the handle, for the caller to judge.
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- **Common services**: configuration access (per-module namespaces from /etc/dpm/conf.d/), logging, module-path queries.
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## Core C API
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## The libdpm-core C API
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All functions are extern "C". All returned strings are owned by core (or by the module that produced them), are valid until the context is closed, and are never freed by the caller. All functions returning int use 0 for success and nonzero error codes; details of the most recent failure are retrievable per-context.
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All functions are extern "C". All returned strings are owned by libdpm-core (or by the module that produced them), are valid until the context is closed, and are never freed by the caller. All functions returning int use 0 for success and nonzero error codes; details of the most recent failure are retrievable per-context.
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### Context lifecycle
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**dpm_ctx\* dpm_open(const dpm_open_overrides\* overrides)**
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Creates a core context. Reads configuration from /etc/dpm/conf.d/ (or the config directory named in overrides), resolves the module path (overrides take precedence over config, config over the built-in default), and initializes logging per configuration. Performs no module loading. Returns NULL only on allocation failure or an unreadable/invalid explicit override; a missing config directory is not an error — defaults apply. `overrides` may be NULL, and may specify: config directory, module path, target root (for chroot/image/sysroot operation), and log level. Multiple simultaneous contexts with different roots are legal.
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Creates a libdpm-core context. Reads configuration from /etc/dpm/conf.d/ (or the config directory named in overrides), resolves the module path (overrides take precedence over config, config over the built-in default), and initializes logging per configuration. Performs no module loading. Returns NULL only on allocation failure or an unreadable/invalid explicit override; a missing config directory is not an error — defaults apply. `overrides` may be NULL, and may specify: config directory, module path, target root (for chroot/image/sysroot operation), and log level. Multiple simultaneous contexts with different roots are legal.
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**void dpm_close(dpm_ctx\* ctx)**
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Releases the context: unloads every module handle it issued, closes log targets, frees all memory owned by the context. All handles and strings obtained through the context are invalid after this call. NULL is a no-op.
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### Module acquisition
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**dpm_module\* dpm_require(dpm_ctx\* ctx, const char\* name, const char\* min_version)**
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Resolves the module `name` in the module path, runs the full load-time validation sequence (see Load-time enforcement) if the module is not already loaded in this context, and checks that the module's version is ≥ `min_version` (X.Y.Z comparison; NULL means "any version"). On success returns a module handle owned by the context (repeated calls return the same handle — modules are loaded at most once per context). On failure returns NULL and records the precise reason: not found, validation step failed (with the step and detail), or version below minimum (with both versions).
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**dpm_module\* dpm_require(dpm_ctx\* ctx, const char\* name)**
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Resolves the module `name` in the module path and runs the full load-time validation sequence (see Load-time enforcement) if the module is not already loaded in this context. On success returns a module handle owned by the context (repeated calls return the same handle — modules are loaded at most once per context). On failure returns NULL and records the precise reason: not found, or validation step failed with the step and detail. No version criterion is applied here; compatibility is the caller's to determine from the reported version.
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**int dpm_module_info_of(dpm_ctx\* ctx, dpm_module\* mod, dpm_module_info\* out)**
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Fills `out` with the loaded module's name, version, description, and minimum-libdpm-core version exactly as they were read at load (string pointers valid until context close). This is how a consumer obtains the version it will judge. libdpm-core attaches no meaning to the values. Returns 0 on success, nonzero if the module cannot be reported on.
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**const void\* dpm_get_api(dpm_ctx\* ctx, dpm_module\* mod, const char\* api_name, int table_version)**
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Returns the API table `api_name` at `table_version` from a loaded module — the pointer the module exported for that table, already validated (manifest cross-check, magic, minimum size) at load. The caller casts it to the table struct type for that API and version as defined in the module's documented API. Returns NULL if the module does not provide that api/version pair; that fact is known from the manifest without further probing. The table is valid for the life of the context.
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**int dpm_execute(dpm_ctx\* ctx, dpm_module\* mod, const char\* command, int argc, char\*\* argv)**
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Generic dispatch: invokes the module's dpm_module_execute with the context, `command`, and the argument vector. Returns the module's return value verbatim (0 = success). Core adds nothing to the call besides delivery; argument semantics beyond "argv[0] is the command" are the module's to define.
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Generic dispatch: invokes the module's dpm_module_execute with the context, `command`, and the argument vector. Returns the module's return value verbatim (0 = success). libdpm-core adds nothing to the call besides delivery; argument semantics beyond "argv[0] is the command" are the module's to define.
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### Enumeration
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@@ -78,7 +81,7 @@ Generic dispatch: invokes the module's dpm_module_execute with the context, `com
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Scans the module path and returns a cursor over all *valid* modules (each candidate .so is validated on first scan; failures are logged and excluded). Returns NULL on an unreadable module path.
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**int dpm_cursor_next(dpm_cursor\* cur, dpm_module_info\* out)**
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Advances the cursor. Fills `out` with the next module's name, version, description, and minimum-core version (string pointers valid until context close). Returns 0 and fills `out` while entries remain; returns nonzero at end.
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Advances the cursor. Fills `out` with the next module's name, version, description, and minimum-libdpm-core version (string pointers valid until context close). Returns 0 and fills `out` while entries remain; returns nonzero at end.
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**void dpm_cursor_free(dpm_cursor\* cur)**
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Releases the cursor. NULL is a no-op.
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@@ -86,10 +89,10 @@ Releases the cursor. NULL is a no-op.
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### Services (available to modules and external consumers alike)
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**const char\* dpm_core_version(void)**
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Returns core's own version as a static X.Y.Z string. Callable without a context.
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Returns the libdpm-core version as a static X.Y.Z string. Callable without a context.
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**const char\* dpm_config_get(dpm_ctx\* ctx, const char\* module, const char\* section, const char\* key)**
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Returns the configured value for `key` in `section` of the named module's config namespace (/etc/dpm/conf.d/<module>.conf; "core" names core's own file). Returns NULL if unset. String valid until context close.
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Returns the configured value for `key` in `section` of the named module's config namespace (/etc/dpm/conf.d/<module>.conf; the namespace "core", from core.conf, is the library's own). Returns NULL if unset. String valid until context close.
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**void dpm_log(dpm_ctx\* ctx, int level, const char\* message)**
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Writes `message` at `level` (FATAL=0, ERROR=1, WARN=2, INFO=3, DEBUG=4) to the context's configured log targets (console and/or file). Messages above the configured level are dropped. NULL message is a no-op.
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@@ -102,42 +105,42 @@ Returns a human-readable description of the most recent failure recorded on this
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## Module contract
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A module is one .so in the module directory. It exports, as extern "C", the following reserved symbols. Returned strings are static or module-owned, non-NULL, and valid for the lifetime of the loaded module; core and consumers never free them.
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A module is one .so in the module directory. It exports, as extern "C", the following reserved symbols. Returned strings are static or module-owned, non-NULL, and valid for the lifetime of the loaded module; libdpm-core and consumers never free them.
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**int dpm_module_execute(dpm_ctx\* ctx, const char\* command, int argc, char\*\* argv)**
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The module's generic command entry point. `ctx` is the host context that dispatched the call — the module reaches every core service (dpm_log, dpm_config_get, dpm_module_path, ...) through it. `command` is the subcommand name (equal to argv[0] when argc > 0); argc/argv are the remaining CLI-style arguments. NULL or empty `command` must behave as the module's help command. Returns 0 on success, nonzero on failure. This is the only entry the CLI path ever uses; it must be callable immediately after load with no other setup.
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The module's generic command entry point. `ctx` is the host context that dispatched the call — the module reaches every libdpm-core service (dpm_log, dpm_config_get, dpm_module_path, ...) through it. `command` is the subcommand name (equal to argv[0] when argc > 0); argc/argv are the remaining CLI-style arguments. NULL or empty `command` must behave as the module's help command. Returns 0 on success, nonzero on failure. This is the only entry the CLI path ever uses; it must be callable immediately after load with no other setup.
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**const char\* dpm_module_version(void)**
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Returns the module's own version as an X.Y.Z string. Must be constant for the life of the module and must match the version by which consumers state minimums.
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Returns the module's own version as an X.Y.Z string. Must be constant for the life of the module. This is the value libdpm-core reports to consumers, and the value they judge compatibility against.
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**const char\* dpm_module_description(void)**
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Returns a one-line human-readable description, used in module listings.
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**const char\* dpm_module_core_min(void)**
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Returns the minimum core version (X.Y.Z) this module supports — the oldest core whose contract and services the module was written against. Core refuses to load the module if its own version is lower, and says so.
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Returns the minimum libdpm-core version (X.Y.Z) this module supports — the oldest one whose contract and services the module was written against. A libdpm-core older than that refuses to load the module, and says so.
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**const dpm_manifest\* dpm_module_manifest(void)**
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Returns a pointer to a static manifest table declaring the module's entire functional surface: an entry count and, per entry, the API name, its table version, and the exact exported symbol that carries the table (e.g. { "raw", 1, "raw_api_v1" }). Core trusts nothing it doesn't verify: every declared symbol is resolved at load, and only manifest-declared tables are ever handed to consumers. An API absent from the manifest does not exist, even if its symbol does.
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Returns a pointer to a static manifest table declaring the module's entire functional surface: an entry count and, per entry, the API name, its table version, and the exact exported symbol that carries the table (e.g. { "raw", 1, "raw_api_v1" }). libdpm-core trusts nothing it doesn't verify: every declared symbol is resolved at load, and only manifest-declared tables are ever handed to consumers. An API absent from the manifest does not exist, even if its symbol does.
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**API tables** (the module's functional surface): for each API version, one exported symbol (e.g. raw_api_v1) pointing to a plain C struct of function pointers. Every table opens with two fixed members: a magic constant (a fixed value defined by this spec, confirming the exporter agrees on table layout conventions) and the struct size in bytes (populated by the module, letting consumers accept tail-extended revisions of the same version). All parameters and returns are C types only; state passes through opaque handles; errors are int codes.
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||||
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||||
**Symbol naming**: functional exports are prefixed with the module's name (raw_\*, pkg_\*); the dpm_ prefix is reserved for the contract and core.
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**Symbol naming**: functional exports are prefixed with the module's name (raw_\*, pkg_\*); the dpm_ prefix is reserved for the contract and libdpm-core.
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## Load-time enforcement
|
||||
|
||||
Core is the sole authority on module validity; the contract above is enforced by core's validator, not by any SDK. Validation is all-or-nothing; a module is registered only after passing every step:
|
||||
libdpm-core is the sole authority on module validity; the contract above is enforced by its validator, not by any SDK. Validation is all-or-nothing; a module is registered only after passing every step:
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||||
|
||||
1. **Resolve all reserved contract symbols.** Any missing → refuse, log the exact list, dlclose.
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2. **Core-minimum handshake.** dpm_module_core_min() must be ≤ core's version. If core is too old, refuse and say so — the remedy is updating core, and the message names it. Old modules on newer core always pass.
|
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2. **Minimum-version handshake.** dpm_module_core_min() must be ≤ the running libdpm-core version. If the library is too old, refuse and say so — the remedy is updating libdpm-core, and the message names it. Old modules on a newer libdpm-core always pass.
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3. **Probe the cheap calls.** dpm_module_version() and dpm_module_description() are invoked immediately; NULL or malformed returns → refuse.
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4. **Cross-check the manifest.** Every API the module declares must actually resolve via dlsym. A module advertising an API it doesn't export is refused. Core validates the module's entire declared surface at load, before offering any of it.
|
||||
4. **Cross-check the manifest.** Every API the module declares must actually resolve via dlsym. A module advertising an API it doesn't export is refused. libdpm-core validates the module's entire declared surface at load, before offering any of it.
|
||||
5. **Table sanity.** Check each declared table's magic constant (catches modules built against a stale or wrong layout) and minimum size for its version.
|
||||
|
||||
Failures happen at install/load time, loudly and itemized. Consumers never receive a partially valid module: if core handed out a handle, the contract already validated. The residual C-ABI limit — dlsym cannot verify signatures — is covered in practice by the magic, size, core-minimum handshake, and probes; defeating those requires deliberate lying, which is a package-signing concern upstream of the loader.
|
||||
Failures happen at install/load time, loudly and itemized. Consumers never receive a partially valid module: if a handle was handed out, the contract already validated. The residual C-ABI limit — dlsym cannot verify signatures — is covered in practice by the magic, size, minimum-version handshake, and probes; defeating those requires deliberate lying, which is a package-signing concern upstream of the loader.
|
||||
|
||||
## Module: raw — the file-based installer
|
||||
|
||||
Ships with the base system alongside core. Depends on the baseline only; archive decompression is vendored in, and the package format is chosen to keep that small. This is what makes barren-environment operation possible: core + raw function with nothing else present.
|
||||
Ships with the base system alongside libdpm-core. Depends on the baseline only; archive decompression is vendored in, and the package format is chosen to keep that small. This is what makes barren-environment operation possible: libdpm-core plus raw function with nothing else present.
|
||||
|
||||
- **Owns the backing tree** (/var/lib/dpm/): one directory per installed package holding manifest, metadata, and hooks. The tree is the database at this layer.
|
||||
- **Operations** (exposed both as commands and in raw_api_v1): install a package file, remove, verify, and queries answered by walking the tree — slow but always correct, zero dependencies.
|
||||
@@ -145,9 +148,9 @@ Ships with the base system alongside core. Depends on the baseline only; archive
|
||||
|
||||
## Module: pkg — the full package manager
|
||||
|
||||
Ships as a package, installed by raw once sqlite3 is installed. Requires raw (via core, minimum version) and libsqlite3.
|
||||
Ships as a package, installed by raw once sqlite3 is installed. Requires raw (via libdpm-core, judging raw's reported version itself) and libsqlite3.
|
||||
|
||||
- Never touches the tree directly: every filesystem mutation is a call into raw's API table, obtained from core, in-process — shared locking, real error propagation, no output parsing.
|
||||
- Never touches the tree directly: every filesystem mutation is a call into raw's API table, obtained from libdpm-core, in-process — shared locking, real error propagation, no output parsing.
|
||||
- **The sqlite database is a derived cache** under one invariant: it contains nothing that cannot be rebuilt by scanning the tree. It records the last journal generation it applied; on open, if the tree is ahead (someone used raw directly — explicitly allowed, that's the escape hatch for broken systems), it replays or rebuilds. Self-healing by construction.
|
||||
- Adds what the cache enables: fast queries, dependency resolution against the installed set, multi-package transactions with rollback.
|
||||
- Exposes pkg_api_v1 for consumers that want dependency-aware operations; they transitively get raw's guarantees because there is no second code path to the tree.
|
||||
@@ -161,11 +164,12 @@ Ships as a package, installed by raw once sqlite3 is installed. Requires raw (vi
|
||||
Build systems and Dark Horse components link libdpm-core.so — the same library, the same path as everything else:
|
||||
|
||||
- open a context (optionally against an alternate root),
|
||||
- require the layer they need at a minimum version,
|
||||
- require the layer they need,
|
||||
- read its reported version and decide whether it suits them,
|
||||
- fetch its API table,
|
||||
- call C functions directly.
|
||||
|
||||
Core installs its header to the standard include path and its library to the standard lib path: a consumer writes #include <dpm/core.h>, links -ldpm-core, and calls package manager module functions. A consumer that opens a default context (no overrides) is operating the installed package manager itself — system configuration, system module path, system tree, system locking — exactly as if it were invoking the installed dpm command, because the CLI is just another caller of the same library. Overrides redirect individual paths only when a caller explicitly sets them. Whether a consumer targets raw only (image builders that just deploy trees) or pkg (dependency-aware tooling) is their choice of require(); behavior is identical to the CLI's because it is the same implementation.
|
||||
libdpm-core installs its header to the standard include path and its library to the standard lib path: a consumer writes #include <dpm/core.h>, links -ldpm-core, and calls package manager module functions. A consumer that opens a default context (no overrides) is operating the installed package manager itself — system configuration, system module path, system tree, system locking — exactly as if it were invoking the installed dpm command, because the CLI is just another caller of the same library. Overrides redirect individual paths only when a caller explicitly sets them. Whether a consumer targets raw only (image builders that just deploy trees) or pkg (dependency-aware tooling) is their choice of require(); behavior is identical to the CLI's because it is the same implementation.
|
||||
|
||||
## Bootstrap chain
|
||||
|
||||
@@ -173,33 +177,33 @@ Core installs its header to the standard include path and its library to the sta
|
||||
minimal start: dpm + libdpm-core.so + raw module (baseline deps only)
|
||||
raw installs: sqlite3 package
|
||||
raw installs: dpm-pkg package (drops the pkg module .so)
|
||||
now: core discovers pkg, validates it, full management is live
|
||||
now: libdpm-core discovers pkg, validates it, full management is live
|
||||
```
|
||||
|
||||
Every layer is a package installed and upgraded by the layer beneath it; the package manager maintains itself with the same mechanism it offers the OS. Future modules follow the identical pattern — a repo/network module declares its requirements (pkg, a TLS library), lands as a package, and the capability appears on next discovery.
|
||||
|
||||
## Repository structure
|
||||
|
||||
Modules are developed independently from each other and independently from core — one repository per module, plus the core repository. Each repo owns its source, build, and tests, and produces exactly one artifact:
|
||||
Modules are developed independently from each other and independently from libdpm-core — one repository per module, plus the libdpm-core repository. Each repo owns its source, build, and tests, and produces exactly one artifact:
|
||||
|
||||
- **Core repository**: libdpm-core.so and the dpm CLI. Contains no module code. Its test fixtures include deliberately broken stub modules for validating the loader, and one known-good stub — never a real package module.
|
||||
- **The exception**: an info module that bundles with core, used for testing and reporting functionality of core.
|
||||
- **The libdpm-core repository**: libdpm-core.so and the dpm binary. Contains no module code. Its test fixtures include deliberately broken stub modules for validating the loader, and one known-good stub — never a real package module.
|
||||
- **The exception**: an info module that bundles with the dpm binary and libdpm-core, used to test and demonstrate full DPM system functionality where appropriate.
|
||||
- **One repository per module** (raw, pkg, and every future module): produces that module's .so. Links libdpm-core.so — the only cross-repo build dependency in the system — and nothing else from DPM. Peer modules never appear in a module's repository, build, or test environment; peers are runtime concerns, faked at test time (contract fakes and stub modules) and real only at distribution-level integration.
|
||||
|
||||
No repository can block another's development: a module builds and its full pre-integration test surface (unit, contract, module-hosting) runs with nothing present but its own checkout and an installed or vendored libdpm-core. Release coordination happens through the versioning model — minimums only — rather than through lockstep builds.
|
||||
No repository can block another's development: a module builds and its full pre-integration test surface (unit, contract, module-hosting) runs with nothing present but its own checkout and an installed or vendored libdpm-core. Release coordination happens through the versioning model — each consumer judging the versions it is handed — rather than through lockstep builds.
|
||||
|
||||
### Core repository layout
|
||||
### Layout of the libdpm-core repository
|
||||
|
||||
```
|
||||
include/dpm/ public headers — installed to the system include path; the
|
||||
dpm/ directory is the consumer namespace, so an installed
|
||||
consumer writes #include <dpm/core.h>
|
||||
include/internal/ library-private headers — used only by src/, never installed
|
||||
src/ implementations of the core library
|
||||
src/ implementations of the library
|
||||
src/cli/ the dpm CLI entry point
|
||||
src/bundled-modules/info/ the bundled info module
|
||||
data/ files installed as-is (core.conf)
|
||||
tests/ fixture modules, the core API test binary, CLI tests
|
||||
tests/ fixture modules, the API test binary, CLI tests
|
||||
docs/ project documentation
|
||||
```
|
||||
|
||||
@@ -207,7 +211,7 @@ Every header lives under include/: include/dpm/ is the published API surface and
|
||||
|
||||
## Artifacts
|
||||
|
||||
Terminology: **DPM Core** names the dpm CLI binary; **libdpm-core** names the library.
|
||||
Terminology: **the dpm binary** names the command-line tool; **libdpm-core** names the library.
|
||||
|
||||
| Artifact | Location on system |
|
||||
|---|---|
|
||||
@@ -222,36 +226,36 @@ Development works because the design has no build-time coupling between peers: n
|
||||
|
||||
### What a build requires
|
||||
|
||||
- A module compiles against its own declarations (written to the spec — the externs it exports, the table structs it consumes) plus **libdpm-core.so, the one real link dependency** — and core is by definition the stable, always-present, baseline-only piece. Cheap to have in every dev environment, trivially vendorable as a checkout.
|
||||
- Peer modules are reached at runtime through core's require/get_api. Building pkg does not require raw to exist anywhere. The compile-time knowledge of raw is just the raw_api_v1 struct layout, which is spec, not artifact.
|
||||
- A module compiles against its own declarations (written to the spec — the externs it exports, the table structs it consumes) plus **libdpm-core.so, the one real link dependency** — and libdpm-core is by definition the stable, always-present, baseline-only piece. Cheap to have in every dev environment, trivially vendorable as a checkout.
|
||||
- Peer modules are reached at runtime through the require/get_api pair. Building pkg does not require raw to exist anywhere. The compile-time knowledge of raw is just the raw_api_v1 struct layout, which is spec, not artifact.
|
||||
|
||||
A module repo therefore builds self-contained, always.
|
||||
|
||||
### Test layers
|
||||
|
||||
**1. Unit tests — need nothing.** The module's implementation compiles once as an object library, linked into both the .so and a test binary. Pure logic, error paths, parsing — no core, no peers.
|
||||
**1. Unit tests — need nothing.** The module's implementation compiles once as an object library, linked into both the .so and a test binary. Pure logic, error paths, parsing — no libdpm-core, no peers.
|
||||
|
||||
**2. Contract tests — need a struct, not a module.** Because every dependency is an API table — a plain struct of function pointers — a fake is just a struct the test fills in with functions that record calls and return canned results. pkg's logic is exercised against a fake raw_api_v1 (verifying it calls install/remove/query correctly, handles raw's error codes, honors the journal-generation protocol) with raw nowhere on the machine. Injection is built into the architecture; no linker seams required.
|
||||
|
||||
**3. Module-hosting tests — need core only.** A harness links the real libdpm-core, points the module path at the build output plus fixtures, and has core load the just-built .so exactly as production would — full five-step validation included, so contract violations fail here, in CI, not on a user's system. Where the module needs a peer, the fixture directory contains a **stub module**: a tiny .so exporting the reserved symbols and a fake table, which core validates and serves like the real thing. The harness then drives dpm_module_execute end to end against fixture config and data. This layer runs on a bare builder with nothing installed.
|
||||
**3. Module-hosting tests — need libdpm-core only.** A harness links the real libdpm-core, points the module path at the build output plus fixtures, and has it load the just-built .so exactly as production would — full five-step validation included, so contract violations fail here, in CI, not on a user's system. Where the module needs a peer, the fixture directory contains a **stub module**: a tiny .so exporting the reserved symbols and a fake table, which libdpm-core validates and serves like the real thing. The harness then drives dpm_module_execute end to end against fixture config and data. This layer runs on a bare builder with nothing installed.
|
||||
|
||||
**4. Integration — the only layer that needs everything, and it builds itself.** Real core + real raw, then the actual bootstrap chain into a scratch root: dpm_open against an alternate root, raw installs sqlite3 and the pkg package into it, core discovers pkg, real operations run against the throwaway tree. Because alternate roots are first-class in the API, this needs a directory, not a VM. Full-distribution CI does the same with real packages.
|
||||
**4. Integration — the only layer that needs everything, and it builds itself.** Real libdpm-core plus real raw, then the actual bootstrap chain into a scratch root: dpm_open against an alternate root, raw installs sqlite3 and the pkg package into it, libdpm-core discovers pkg, real operations run against the throwaway tree. Because alternate roots are first-class in the API, this needs a directory, not a VM. Full-distribution CI does the same with real packages.
|
||||
|
||||
### Day-to-day workflow
|
||||
|
||||
- Working on **pkg**: edit, run unit + contract tests (instant, zero environment), harness run before merge. A real raw is never needed, or even possessed, until integration.
|
||||
- Working on **raw**: same, except its fakes point the other way — its tests need only fixture package files and a scratch tree.
|
||||
- Working on **core**: its test fixtures are deliberately broken modules — missing symbols, wrong magic, lying manifests, too-new core-min — plus one known-good stub. Core development never needs any real package module.
|
||||
- Working on **libdpm-core**: its test fixtures are deliberately broken modules — missing symbols, wrong magic, lying manifests, a too-new minimum-version declaration — plus one known-good stub. Development never needs any real package module.
|
||||
- **Debugging** is the layer-3 harness under a debugger — it is the "run the module without the system" mechanism, so no separate standalone build exists or is maintained.
|
||||
|
||||
The discipline that keeps this honest: fakes and stubs are written to the spec, and layer-3 validation plus the layer-4 bootstrap run in CI, so a fake that drifts from reality is caught by the first integration pass rather than shipped.
|
||||
|
||||
## Development capabilities
|
||||
|
||||
During development the CLI must be pointable at a local libdpm-core, and that core must be configurable to local paths (module path, config dir, etc.). Two mechanisms provide this:
|
||||
During development the CLI must be pointable at a local libdpm-core, and that library must be configurable to local paths (module path, config dir, etc.). Two mechanisms provide this:
|
||||
|
||||
- **Pointing the CLI at a local libdpm-core** is dynamic-linker territory, needing no DPM mechanism: development builds of the CLI carry an rpath to their own build tree's lib/ directory, so the locally built binary resolves the locally built core (LD_LIBRARY_PATH pointed at that lib/ directory achieves the same). The system core is never touched.
|
||||
- **Pointing that core at local paths** is what the dpm_open overrides exist for: config directory, module path, and target root are all fields of the overrides struct, and the CLI exposes them as flags. A dev invocation:
|
||||
- **Pointing the CLI at a local libdpm-core** is dynamic-linker territory, needing no DPM mechanism: development builds of the CLI carry an rpath to their own build tree's lib/ directory, so the locally built binary resolves the locally built library (LD_LIBRARY_PATH pointed at that lib/ directory achieves the same). The system libdpm-core is never touched.
|
||||
- **Pointing that library at local paths** is what the dpm_open overrides exist for: config directory, module path, and target root are all fields of the overrides struct, and the CLI exposes them as flags. A dev invocation:
|
||||
|
||||
```
|
||||
./build/bin/dpm --config-dir ./tests/fixtures/conf --module-path ./build/modules raw install ./fixture.dpm
|
||||
@@ -264,13 +268,13 @@ The config-dir override matters most: once the context reads config from the loc
|
||||
## Evolution rules
|
||||
|
||||
- **Append-only ABI**: breaking a module API means exporting a new table (raw_api_v2) beside the old one, never mutating v1. Old tables remain until consumers are gone.
|
||||
- **Append-only core contract**: newer core loads everything older core did; a module's only version assertion against core is its minimum.
|
||||
- **Minimums only, everywhere**: modules declare the minimum core they support; consumers declare the minimum module version they need. No maximums, no exact-match constraints — an update can never make a previously working combination refuse to load.
|
||||
- **Append-only libdpm-core contract**: a newer libdpm-core loads everything an older one did; a module's only version assertion against the library is its minimum.
|
||||
- **Compatibility is decided by the consumer**: modules declare the minimum libdpm-core they support, and the library enforces that one handshake because it is the host. Everything else is reported, not enforced — libdpm-core hands a consumer the version it saw and the consumer decides whether to proceed. No maximums and no exact-match constraints live in the library, so an update can never make a previously working combination refuse to load.
|
||||
|
||||
## Invariants
|
||||
|
||||
1. Core routes and hosts; modules implement. No package logic in core, ever.
|
||||
2. Writes flow down, never sideways: a layer mutates the system only through the layer beneath it, in-process through core-mediated APIs.
|
||||
1. libdpm-core routes and hosts; modules implement. No package logic in the library, ever.
|
||||
2. Writes flow down, never sideways: a layer mutates the system only through the layer beneath it, in-process through libdpm-core-mediated APIs.
|
||||
3. Truth lives in the tree; everything above is regenerable cache or convenience.
|
||||
4. Dropping down a layer by hand is always legal; layers above detect it and reconcile.
|
||||
5. A module is either fully valid or not loaded — no partial states, no consumer-side defense.
|
||||
|
||||
@@ -1,27 +1,27 @@
|
||||
# Developing DPM Modules
|
||||
|
||||
A DPM module is one shared object in the module directory. Core loads it, validates it completely, routes CLI commands to it, and serves its functions to other modules and to programs linked against libdpm-core. This document covers writing, building, testing, and installing a module.
|
||||
A DPM module is one shared object in the module directory. libdpm-core loads it, validates it completely, routes commands to it, and serves its functions to other modules and to programs linked against libdpm-core. This document covers writing, building, testing, and installing a module.
|
||||
|
||||
## The module contract
|
||||
|
||||
Every module exports the following symbols as extern "C". All returned strings must be non-NULL, static or module-owned, and valid for the lifetime of the loaded module; callers never free them.
|
||||
|
||||
**int dpm_module_execute(dpm_ctx\* ctx, const char\* command, int argc, char\*\* argv)**
|
||||
The generic command entry point. `ctx` is the host context that dispatched the call; the module reaches every core service (dpm_log, dpm_config_get, dpm_module_path, ...) through it. `command` is the subcommand name, equal to argv[0] when argc > 0. NULL or empty `command` must behave as the module's help command. Returns 0 on success, nonzero on failure. It must be callable immediately after load with no other setup.
|
||||
The generic command entry point. `ctx` is the host context that dispatched the call; the module reaches every libdpm-core service (dpm_log, dpm_config_get, dpm_module_path, ...) through it. `command` is the subcommand name, equal to argv[0] when argc > 0. NULL or empty `command` must behave as the module's help command. Returns 0 on success, nonzero on failure. It must be callable immediately after load with no other setup.
|
||||
|
||||
**const char\* dpm_module_version(void)**
|
||||
The module's own version as an X.Y.Z string. Consumers state minimum-version requirements against this value.
|
||||
The module's own version as an X.Y.Z string. libdpm-core reports this value to consumers, and each consumer decides for itself whether the version suits it.
|
||||
|
||||
**const char\* dpm_module_description(void)**
|
||||
A one-line human-readable description, shown in module listings.
|
||||
|
||||
**const char\* dpm_module_core_min(void)**
|
||||
The minimum core version (X.Y.Z) the module supports — the oldest core whose contract and services it was written against. Core refuses to load the module if its own version is lower, and the refusal message says so.
|
||||
The minimum libdpm-core version (X.Y.Z) the module supports — the oldest one whose contract and services it was written against. A libdpm-core older than that refuses to load the module, and the refusal message says so.
|
||||
|
||||
**const dpm_manifest\* dpm_module_manifest(void)**
|
||||
A static table declaring the module's entire functional surface: an entry count and, per entry, the API name, its table version, and the exact exported symbol carrying the table — for example { "mymodule", 1, "mymodule_api_v1" }. Only manifest-declared tables are ever handed to consumers; an API absent from the manifest does not exist, even if its symbol does. A module providing no API tables returns a manifest with a count of zero.
|
||||
|
||||
The dpm_manifest and dpm_manifest_entry types, the table header, and the core service declarations all come from the installed public header:
|
||||
The dpm_manifest and dpm_manifest_entry types, the table header, and the service declarations all come from the installed public header:
|
||||
|
||||
```
|
||||
#include <dpm/core.h>
|
||||
@@ -33,11 +33,11 @@ A module's functions are published to consumers as API tables: one exported symb
|
||||
|
||||
All parameters and return values crossing a table are C types only. State passes through opaque handles; errors are int codes.
|
||||
|
||||
**Symbol naming**: every functional export is prefixed with the module's name (mymodule_\*). The dpm_ prefix is reserved for the contract symbols and core.
|
||||
**Symbol naming**: every functional export is prefixed with the module's name (mymodule_\*). The dpm_ prefix is reserved for the contract symbols and libdpm-core.
|
||||
|
||||
## Validation at load
|
||||
|
||||
Core is the sole authority on module validity, and validation is all-or-nothing. Before a module is offered to anyone, core verifies, in order: every reserved contract symbol resolves; the core-minimum handshake passes; the version and description probes return well-formed values; every manifest-declared symbol resolves; and every declared table carries the correct magic and a sane size. A module failing any step is refused with an itemized reason, visible in the load-failure output. A module that loads is fully valid — consumers never defend against partial states.
|
||||
libdpm-core is the sole authority on module validity, and validation is all-or-nothing. Before a module is offered to anyone, it verifies, in order: every reserved contract symbol resolves; the minimum-version handshake passes; the version and description probes return well-formed values; every manifest-declared symbol resolves; and every declared table carries the correct magic and a sane size. A module failing any step is refused with an itemized reason, visible in the load-failure output. A module that loads is fully valid — consumers never defend against partial states.
|
||||
|
||||
## Building
|
||||
|
||||
@@ -67,7 +67,9 @@ cmake -B <build-dir>
|
||||
cmake --build <build-dir>
|
||||
```
|
||||
|
||||
libdpm-core is the only DPM link dependency a module ever has. Dependencies on other modules are runtime concerns, resolved through core's require/get_api — a peer module is never linked and never needs to be present to build.
|
||||
libdpm-core is the only DPM link dependency a module ever has. Dependencies on other modules are runtime concerns, resolved through the require/get_api pair — a peer module is never linked and never needs to be present to build.
|
||||
|
||||
A module that depends on a peer is the party that judges the peer's version. Require it, read its reported version with dpm_module_info_of, and decide whether it is too new or too old for the calls you intend to make. libdpm-core reports; it does not rule.
|
||||
|
||||
## Running and testing locally
|
||||
|
||||
@@ -77,12 +79,12 @@ Load the freshly built module through a locally run dpm without installing anyth
|
||||
dpm --module-path <build-dir> mymodule <command>
|
||||
```
|
||||
|
||||
Core runs the full validation sequence on every load, so a contract mistake surfaces here, immediately and itemized, rather than after installation. The --config-dir flag points the module's configuration namespace at local files during development, and --root directs package operations at a scratch tree.
|
||||
libdpm-core runs the full validation sequence on every load, so a contract mistake surfaces here, immediately and itemized, rather than after installation. The --config-dir flag points the module's configuration namespace at local files during development, and --root directs package operations at a scratch tree.
|
||||
|
||||
## Installing
|
||||
|
||||
Modules install to lib/dpm/modules under the install prefix (/usr/lib/dpm/modules on a distribution install). Core discovers the module on its next scan; no registration step exists beyond the file being present and valid.
|
||||
Modules install to lib/dpm/modules under the install prefix (/usr/lib/dpm/modules on a distribution install). libdpm-core discovers the module on its next scan; no registration step exists beyond the file being present and valid.
|
||||
|
||||
## Reference implementation
|
||||
## A working example
|
||||
|
||||
The info module bundled with the core repository at src/bundled-modules/info/ is a complete working example of the contract, an API table, and this build structure.
|
||||
The info module bundled with the dpm binary and libdpm-core, at src/bundled-modules/info/, tests and demonstrates full DPM system functionality, and in doing so shows the contract, an API table, and this build structure in working form.
|
||||
|
||||
151
docs/OVERVIEW.md
151
docs/OVERVIEW.md
@@ -2,87 +2,131 @@
|
||||
|
||||
## What DPM is
|
||||
|
||||
DPM is the package manager for Dark Horse Linux. Its core is **libdpm-core**, a shared library that discovers modules, validates them, routes calls to them, negotiates versions, and provides configuration and logging. Modules — shared objects in the module directory — implement package functionality.
|
||||
DPM is the package manager for Dark Horse Linux. At its center is **libdpm-core**, a shared library that discovers modules, validates them, routes calls to them, reports their versions, and provides configuration and logging. Modules — shared objects in the module directory — implement package functionality.
|
||||
|
||||
The `dpm` command-line tool is one consumer of that library. Build systems, image builders, distribution tooling, and programs in any language with C FFI are equal consumers of the same library through the same interface.
|
||||
**The dpm binary** is the command-line tool, and it is one consumer of that library. Build systems, image builders, distribution tooling, and programs in any language with C FFI are equal consumers of the same library through the same interface.
|
||||
|
||||
Core implements no package operations. It routes and hosts.
|
||||
libdpm-core implements no package operations. It routes and hosts.
|
||||
|
||||
## The shape of the system
|
||||
|
||||
```
|
||||
dpm CLI build systems / DHL tools / other languages
|
||||
\ /
|
||||
v v
|
||||
libdpm-core.so
|
||||
(discovery, validation, routing,
|
||||
version negotiation, config, logging)
|
||||
|
|
||||
v
|
||||
modules
|
||||
(one .so each)
|
||||
the dpm binary build systems / DHL tools / other languages
|
||||
\ /
|
||||
v v
|
||||
libdpm-core.so
|
||||
(discovery, validation, routing,
|
||||
version reporting, config, logging)
|
||||
|
|
||||
v
|
||||
modules
|
||||
(one .so each)
|
||||
```
|
||||
|
||||
Everything passes through core: CLI-to-module, module-to-module, program-to-module. No consumer calls `dlopen`, `dlsym`, or performs module discovery itself.
|
||||
Everything passes through libdpm-core: binary-to-module, module-to-module, program-to-module. No consumer performs module discovery or dynamic loading itself.
|
||||
|
||||
## How it works
|
||||
## Three layers to read this at
|
||||
|
||||
### The context
|
||||
DPM is met at three different layers, and which one you are at determines what any statement below means for you.
|
||||
|
||||
All work happens through a context handle obtained from `dpm_open`. Opening a context reads configuration from `/etc/dpm/conf.d/`, resolves the module directory, and initializes logging. Four things can be overridden at open time — the configuration directory, the module path, the target root, and the log level — and every one is exposed as a flag on the `dpm` command, so anything a linked program can redirect, a developer at a shell can redirect too.
|
||||
- **The user layer** — a person at a shell running the dpm binary. Everything here is a command and its flags.
|
||||
- **The developer layer** — a program written against the C API in `<dpm/core.h>`, linking `-ldpm-core`. Everything here is a function call. Module authors live here too, on the other side of the same boundary.
|
||||
- **The filesystem layer** — the directories and files DPM reads and writes: configuration, the module directory, the target root, and the installed artifacts.
|
||||
|
||||
The target root override is what makes chroot builds, image assembly, and sysroot management work: package operations act on the given tree instead of the running system. Multiple contexts with different roots can be open at once.
|
||||
The sections that follow are labelled by layer. Where a mechanism exists at more than one layer, it is described once at each, because the same idea looks different depending on where you stand.
|
||||
|
||||
The context owns everything it hands out. Every string a consumer receives stays valid until `dpm_close`, and callers never free anything.
|
||||
## How it works at the user layer
|
||||
|
||||
### Acquiring a module
|
||||
The dpm binary's subcommand surface is exactly the set of loadable modules. `dpm <module> <command> [args...]` loads that module and hands the command to it; `dpm <module> help` asks the module to describe itself. There is no fixed list of operations baked into the tool, because the tool contains no capability logic — it parses arguments and prints.
|
||||
|
||||
`dpm_require` resolves a module by name in the module path, validates it completely, and returns a handle — or returns NULL and records exactly why. A minimum version may be stated; NULL accepts any version. Modules load at most once per context, and repeated calls return the same handle.
|
||||
`dpm --list-modules` shows every module that passes validation, with its version and description. Candidates that fail are excluded from the listing and logged, so what is listed is what can actually be run.
|
||||
|
||||
Once a module is loaded, there are two ways to reach it:
|
||||
Four flags redirect the system defaults:
|
||||
|
||||
- **Generic dispatch** — `dpm_execute` passes a command name and an argument vector to the module's entry point. This is the path the CLI uses, and it is why the CLI's command surface is exactly the set of loadable modules.
|
||||
- **Typed access** — `dpm_get_api` returns a plain C struct of function pointers for a named API at a stated version. This is the path modules and external programs use to call functions directly.
|
||||
- `-c, --config-dir PATH` — where configuration is read from
|
||||
- `-m, --module-path PATH` — which directory modules are loaded from
|
||||
- `-r, --root PATH` — the target root that package operations act on
|
||||
- `-L, --log-level LEVEL` — FATAL, ERROR, WARN, INFO, or DEBUG
|
||||
|
||||
### Enumeration
|
||||
These four exist because of a rule the design imposes on itself: every field a linked program can override must also be a flag, so anything reachable from code is reachable from a shell. That rule holds for any override added in the future.
|
||||
|
||||
`dpm_list_modules` scans the module path and yields every valid module with its name, version, description, and minimum core version. Candidates that fail validation are logged and excluded, so a listing shows what can actually be used.
|
||||
## How it works at the developer layer
|
||||
|
||||
### The module contract
|
||||
A program links libdpm-core and includes `<dpm/core.h>`. Everything it does happens through a **context**, an opaque handle obtained from `dpm_open`.
|
||||
|
||||
A module is one `.so` in the module directory that exports five reserved symbols: a command entry point, its own version, a one-line description, the minimum core version it supports, and a manifest. The manifest declares the module's entire functional surface — for each API, its name, table version, and the exact exported symbol carrying the table.
|
||||
Opening a context reads the configuration files, resolves which directory modules will be loaded from, and initializes logging. It loads no modules. The same four things the dpm binary exposes as flags are the fields of the overrides struct passed to `dpm_open`, and passing NULL accepts the system defaults — which is what makes a default context equivalent to invoking the installed dpm binary, since that binary is just another caller doing the same thing.
|
||||
|
||||
The target root override is what makes chroot builds, image assembly, and sysroot management work: package operations act on the given tree instead of the running system. Multiple contexts with different roots may be open at once.
|
||||
|
||||
The context owns everything it hands out. Every string a caller receives stays valid until `dpm_close`, and callers never free anything.
|
||||
|
||||
**Acquiring a module.** `dpm_require` resolves a module by name, validates it completely, and returns a handle — or returns NULL, with `dpm_last_error` carrying the precise reason. Modules load at most once per context, and repeated calls return the same handle.
|
||||
|
||||
**Reading what libdpm-core saw.** `dpm_module_info_of` fills in a module's name, version, description, and minimum-libdpm-core version. Those values are reported, and no conclusion is drawn from them.
|
||||
|
||||
**Calling into a module.** Two paths:
|
||||
|
||||
- `dpm_execute` passes a command name and an argument vector to the module's entry point. This is the path the dpm binary takes.
|
||||
- `dpm_get_api` returns a plain C struct of function pointers for a named API at a stated version. This is the path modules and external programs take to call functions directly.
|
||||
|
||||
**Enumerating.** `dpm_list_modules` yields a cursor over every valid module, which is what backs the listing the dpm binary prints.
|
||||
|
||||
**Services.** A module reaches libdpm-core through the context that dispatched the call: `dpm_log` to write a message, `dpm_config_get` to read a value from its own configuration namespace, `dpm_module_path` to learn where modules live, `dpm_core_version` to learn the library's version. A module needs no file handling and no logging machinery of its own.
|
||||
|
||||
## How it works at the filesystem layer
|
||||
|
||||
**Configuration** lives in `/etc/dpm/conf.d/`. Each `.conf` file in that directory is one namespace named after the file: `core.conf` holds the library's own settings, and a module named `mymodule` reads `mymodule.conf`. Files are sectioned, and a value is addressed by namespace, section, and key. The library's own file carries the log level, whether to write a log file and where, and the default module directory.
|
||||
|
||||
**Modules** live in `/usr/lib/dpm/modules/`. A module's name is its filename without the `.so` extension, so `info.so` is the module named `info`. Discovery is the presence of a valid file in that directory — there is no registry, and no registration step.
|
||||
|
||||
**Logging** goes to the console always, and to a log file when configuration enables one; the default path is `/var/log/dpm/dpm.log`.
|
||||
|
||||
**The target root** defaults to `/`. Pointed elsewhere, it is the tree that package operations act on, which is what turns a scratch directory into a complete target for image assembly or a chroot build.
|
||||
|
||||
**Installed artifacts:**
|
||||
|
||||
| Artifact | Location |
|
||||
|---|---|
|
||||
| the dpm binary | `/usr/bin/dpm` |
|
||||
| `libdpm-core.so` | `/usr/lib/libdpm-core.so` |
|
||||
| public header | `/usr/include/dpm/core.h` |
|
||||
| modules | `/usr/lib/dpm/modules/<name>.so` |
|
||||
|
||||
## The module contract
|
||||
|
||||
*Developer layer, module-author side.*
|
||||
|
||||
A module is one `.so` in the module directory exporting five reserved symbols: a command entry point, its own version, a one-line description, the minimum libdpm-core version it supports, and a manifest. The manifest declares the module's entire functional surface — for each API, its name, table version, and the exact exported symbol carrying the table.
|
||||
|
||||
Beyond those five, a module exports one symbol per API table. A table is a C struct of function pointers opening with a magic constant and the struct's size in bytes as the module compiled it, which lets a consumer accept a tail-extended revision of the same version. Everything crossing a table is a C type; state passes through opaque handles; errors are int codes.
|
||||
|
||||
### Load-time enforcement
|
||||
## Load-time enforcement
|
||||
|
||||
Core validates a module completely before offering it to anyone, in five steps:
|
||||
libdpm-core validates a module completely before offering it to anyone, in five steps:
|
||||
|
||||
1. Every reserved contract symbol resolves.
|
||||
2. The module's minimum core version is not newer than core's own.
|
||||
2. The module's minimum libdpm-core version is not newer than the running library's own.
|
||||
3. The version and description probes return well-formed values.
|
||||
4. Every symbol the manifest declares actually resolves.
|
||||
5. Every declared table carries the correct magic constant and a sane size.
|
||||
|
||||
A module failing any step is refused with an itemized reason and its library handle closed. Validation is all-or-nothing: if core hands out a handle, the contract already passed. Consumers never defend against partially valid modules, because they cannot receive one.
|
||||
A module failing any step is refused with an itemized reason and its library handle closed. Validation is all-or-nothing: if a handle comes back, the contract already passed. Consumers never defend against partially valid modules, because they cannot receive one.
|
||||
|
||||
### Versioning
|
||||
At the user layer this is visible as a module missing from `--list-modules` with a logged reason, or as an itemized failure when the module is named directly.
|
||||
|
||||
Compatibility is directional, and the module is the party that declares it.
|
||||
## Versioning
|
||||
|
||||
Each module states the oldest core it supports. Core compares its own version against that minimum and refuses only when core is older, with a message naming the remedy. Core never rejects a module for being old, because core's contract grows append-only — a newer core supports everything an older core did.
|
||||
libdpm-core enforces exactly one version rule, the one where it is the host: each module states the oldest libdpm-core it supports, and a library older than that refuses to load the module, with a message naming the remedy. A module is never rejected for being old, because the library's contract grows append-only — a newer libdpm-core supports everything an older one did.
|
||||
|
||||
Consumers state minimums and never maximums. Module APIs also evolve append-only: a breaking change means exporting a new table beside the old one rather than mutating the existing one. The consequence is that updating core or any module preserves every combination that previously worked, and the single possible load refusal names its own fix.
|
||||
Every other version question belongs to the consumer. A module that depends on another requires it, reads the version reported back, and decides for itself whether that version is too new or too old for the calls it intends to make. libdpm-core reports what it saw and draws no conclusion from it, so a handle means the module is valid rather than that it suits any particular caller.
|
||||
|
||||
### Configuration and logging
|
||||
|
||||
Configuration lives in per-module namespaces: each module's `.conf` file under the context's configuration directory, with `core` naming core's own file. A module reads its settings through the context that dispatched the call, so a module needs no file handling of its own. Logging works the same way — a module writes through the context, and the context decides the destinations and the threshold.
|
||||
Module APIs evolve append-only: a breaking change means exporting a new table beside the old one rather than mutating the existing one. A newer module therefore still carries everything an older consumer called, so updating libdpm-core or any module preserves every combination that previously worked.
|
||||
|
||||
## Why it works this way
|
||||
|
||||
### Because it must run on a barren system
|
||||
|
||||
The founding constraint is that DPM has to work in an environment providing nothing but libc and libstdc++, using the same binaries that run on a fully populated system. That forbids core from taking on any dependency beyond the baseline, which forbids package logic from living in core, which produces the division the whole architecture rests on: **core routes and hosts, modules implement.** Anything needing a database, compression, or TLS is a module that arrives later.
|
||||
The founding constraint is that DPM has to work in an environment providing nothing but libc and libstdc++, using the same binaries that run on a fully populated system. That forbids libdpm-core from taking on any dependency beyond the baseline, which forbids package logic from living inside it, which produces the division the whole architecture rests on: **libdpm-core routes and hosts, modules implement.** Anything needing a database, compression, or TLS is a module that arrives later.
|
||||
|
||||
### Because capability has to grow in layers
|
||||
|
||||
@@ -90,47 +134,48 @@ Each layer of the system installs the dependencies of the next using only what a
|
||||
|
||||
### Because one implementation must serve every caller
|
||||
|
||||
The requirement that every implementation exist exactly once, and be consumable by the CLI, by other layers, and by external programs, is what makes libdpm-core a C ABI library rather than an application with a library carved out of it. A program that opens a default context is operating the installed package manager itself — system configuration, system module path, system tree, system locking — identically to invoking `dpm`, because `dpm` is just another caller of the same library. The CLI is argument parsing and printing, and no capability logic lives in it.
|
||||
The requirement that every implementation exist exactly once, and be consumable by the dpm binary, by other layers, and by external programs, is what makes libdpm-core a C ABI library rather than an application with a library carved out of it. This is also why the user layer and the developer layer stay in step: the flags are the override fields, one for one, so a developer and a user redirect the same things by the same names.
|
||||
|
||||
### Because nothing may be trusted that has not been verified
|
||||
|
||||
Core is the sole authority on module validity, and the contract is enforced by core's validator rather than by an SDK a module author might skip, patch, or fall behind. That is why validation is all-or-nothing and why it happens at load: failures surface loudly and itemized at install time instead of halfway through an operation on a user's system. The manifest exists so core can check a module's entire declared surface before offering any of it — an API absent from the manifest does not exist, even if its symbol does.
|
||||
libdpm-core is the sole authority on module validity, and the contract is enforced by its validator rather than by an SDK a module author might skip, patch, or fall behind. That is why validation is all-or-nothing and why it happens at load: failures surface loudly and itemized at install time instead of halfway through an operation on a user's system. The manifest exists so a module's entire declared surface can be checked before any of it is offered — an API absent from the manifest does not exist, even if its symbol does.
|
||||
|
||||
The residual limit is that `dlsym` cannot verify a function signature. The magic constant, the size field, the core-minimum handshake, and the probes cover this in practice; defeating them takes deliberate lying, which is a package-signing concern upstream of the loader.
|
||||
The residual limit is that dynamic symbol lookup cannot verify a function signature. The magic constant, the size field, the minimum-version handshake, and the probes cover this in practice; defeating them takes deliberate lying, which is a package-signing concern upstream of the loader.
|
||||
|
||||
### Because updates must never strand a working system
|
||||
|
||||
Minimums everywhere, no maximums, and append-only evolution in both directions mean an update can only add satisfiable states. This is what allows modules to be released independently: coordination happens through the versioning model instead of through lockstep builds.
|
||||
libdpm-core holds no maximums and no exact-match constraints, and evolution is append-only in both directions, so an update can only add satisfiable states. This is what allows modules to be released independently: coordination happens through the versioning model instead of through lockstep builds.
|
||||
|
||||
### Because modules are developed independently
|
||||
|
||||
One repository per module, plus the core repository. A module links libdpm-core and nothing else from DPM; peer modules never appear in its repository, build, or test environment. "Not all the pieces are there" is the normal, permanent condition at build time, so the architecture is arranged to make that a non-event:
|
||||
One repository per module, plus the libdpm-core repository. A module links libdpm-core and nothing else from DPM; peer modules never appear in its repository, build, or test environment. "Not all the pieces are there" is the normal, permanent condition at build time, so the architecture is arranged to make that a non-event:
|
||||
|
||||
- A module compiles against its own declarations plus core.
|
||||
- A module compiles against its own declarations plus libdpm-core.
|
||||
- Every dependency it consumes is a plain struct of function pointers, so a fake is a struct the test fills in — dependency injection is inherent, with no linker seams.
|
||||
- A harness that links real core and points the module path at build output plus fixture stubs exercises the real five-step validation on a bare builder.
|
||||
- A harness that links the real libdpm-core and points the module path at build output plus fixture stubs exercises the real five-step validation on a bare builder.
|
||||
- Only final integration needs the whole system, and because alternate roots are first-class, it needs a directory rather than a virtual machine.
|
||||
|
||||
The core repository's own fixtures are deliberately broken stub modules — missing symbols, bad magic, a lying manifest, a too-new core minimum, a malformed version — plus one known-good stub. Core development never requires a real package module to exist.
|
||||
This repository's own fixtures are deliberately broken stub modules — missing symbols, bad magic, a lying manifest, a too-new minimum version, a malformed version — plus one known-good stub. Developing libdpm-core never requires a real package module to exist.
|
||||
|
||||
## What the core repository produces
|
||||
## What this repository produces
|
||||
|
||||
- **libdpm-core.so** — the library
|
||||
- **dpm** — the command-line tool
|
||||
- **the dpm binary** — the command-line tool
|
||||
- **info** — a module bundled with the dpm binary and libdpm-core, used to test and demonstrate full DPM system functionality where appropriate
|
||||
|
||||
Every other module is developed against libdpm-core and lives outside this repository.
|
||||
|
||||
## Invariants
|
||||
|
||||
1. Core routes and hosts; modules implement. No package logic in core, ever.
|
||||
2. Writes flow down, never sideways: a layer mutates the system only through the layer beneath it, in-process through core-mediated APIs.
|
||||
1. libdpm-core routes and hosts; modules implement. No package logic inside it, ever.
|
||||
2. Writes flow down, never sideways: a layer mutates the system only through the layer beneath it, in-process through mediated APIs.
|
||||
3. A module is either fully valid or not loaded — no partial states, no consumer-side defense.
|
||||
4. Anything a linked program can redirect, a shell user can redirect too.
|
||||
|
||||
## Further reading
|
||||
|
||||
- **DESIGN.md** — the full design specification
|
||||
- **CONSUMERS.md** — linking libdpm-core and driving it from a program
|
||||
- **MODULES.md** — writing, building, testing, and installing a module
|
||||
- **BUILD.md** — building, testing, and installing core itself
|
||||
- **BUILD.md** — building, testing, and installing libdpm-core and the dpm binary
|
||||
- **DOCUMENTATION.md** — generating the code reference
|
||||
|
||||
Reference in New Issue
Block a user
