2026.10.1.2: a pack states its build, every drive takes the job count, and a unit's compile does not depend on the member selection (#751, #753)

Implements .agents/docs/2026-10-01-pack-drive-and-selection-independent-compile-design.md.

- Every ninja drive takes the job count and the stale-token reclaim from the
  plan, and is reported whenever the command opened the report, unless its
  caller states that it writes its own lines (mcpp test's per-test drives).
- mcpp pack states its build: package lines, the status row, and Finished
  before the first Packing line; one Finished for several configurations; the
  dispatch pass is reported; a pack fills the global dependency cache.
- Every package's BMIs lie below its own directory except the root's, as
  object files do since #233; a unit reads one module map of what it reaches
  through its imports (a GCC mapper, or a clang/MSVC argument file).
- A file a member lists from outside its directory belongs to that member, not
  to the workspace's virtual root.
- Position independence follows the target: every unit of an ELF target that
  is not freestanding is compiled with -fPIC.

Author: speak-agent

.agents/docs/2026-10-01-pack-drive-and-selection-independent-compile-design.md

@@ -18,7 +18,7 @@ superseded_by: 2026-09-07-....md  # when status is superseded
 ---
 ```
 
-321 records.
+322 records.
 
 ## By subject
 
@@ -30,6 +30,7 @@ Records that declare one. Everything else is listed by date below.
 
 ### design
 
+- [A pack's build reported as a build, and a unit's compile independent of the member selection: triage and design (#753, #751)](2026-10-01-pack-drive-and-selection-independent-compile-design.md) — active
 - [Member selection, build programs prepared once, a pack over several members, and the output streams of `mcpp run`: the plan for the release after 2026.9.30.2 (#748, #749, #750)](2026-09-30-member-selection-and-build-program-cost-plan.md) — landed
 - [The build's wall time, its progress count, a hang after the build, and #732 and #744: measurements and a remediation plan](2026-09-30-build-wall-time-progress-count-and-hang-plan.md) — landed
 - [Build output, revision 3: every package that does work is named, the live display is one line drawn in one write, and a repeated warning is stated once per file](2026-09-30-build-output-refinement-design.md) — landed
@@ -110,6 +111,9 @@ Records that declare one. Everything else is listed by date below.
 
 ## By date
 
+### 2026-10
+
+- [A pack's build reported as a build, and a unit's compile independent of the member selection: triage and design (#753, #751)](2026-10-01-pack-drive-and-selection-independent-compile-design.md) — active
 ### 2026-09
 
 - [Member selection, build programs prepared once, a pack over several members, and the output streams of `mcpp run`: the plan for the release after 2026.9.30.2 (#748, #749, #750)](2026-09-30-member-selection-and-build-program-cost-plan.md) — landed

.agents/docs/README.md

@@ -4,6 +4,72 @@
 > Each `## [<version>]` section is that release's notes. Entries are written in English
 > from 2026.9.28.3 on; earlier entries remain as written.
 
+## [2026.10.1.2] - 2026-10-01
+
+This release implements the design for a pack's build and a compile that does
+not depend on the member selection
+(`.agents/docs/2026-10-01-pack-drive-and-selection-independent-compile-design.md`),
+and resolves mcpp#751 and mcpp#753. A project that imports a module of a
+dependency, and every project on an ELF target, is compiled once more after the
+upgrade, because its commands change (both under **Changed**).
+
+### Fixed
+
+- **A unit is compiled by the same command in every selection of a
+  workspace.** The selections of one configuration share a build directory,
+  and three facts about the whole graph reached the commands of members they
+  did not concern, so each switch between `--workspace` and `-p` recompiled
+  them (mcpp#751; GalTranslPP 3.1.3 recompiled its core for 3m22s):
+  - a module name that two members provide moved every BMI of that name below
+    its provider's directory, and told the importers so, only when the graph
+    held both providers;
+  - a file that a member lists from outside its own directory was owned by the
+    workspace's virtual root, whose object census depended on how many members
+    listed it;
+  - a member that builds a shared library put `-fPIC` on every unit of the
+    graph.
+  A command now depends on the unit's package, the packages it reaches, the
+  features the selection activates for it and the declarations a selected
+  member holds as the root, and on nothing else in the graph. `mcpp build
+  --workspace` followed by `mcpp build -p <member>` compiles nothing, and so
+  does any alternation of selections (e2e 872).
+- **`mcpp pack` states the build it performs.** Its build wrote no package
+  line, no status row and no `Finished`, so a release job whose pack
+  recompiled mcpp showed `Planning` for six minutes (mcpp#753). A pack is now
+  stated as `mcpp build` states one, with `Finished` before the first `Packing`
+  line and one `Finished` for a pack over several configurations; the second
+  pass of a dispatched `--format` is stated in the same way (e2e 871).
+- **`[build] jobs` bounds every command that compiles.** `mcpp test` and
+  `mcpp pack` ran ninja's default number of jobs whatever `[build] jobs`,
+  `--jobs` or `MCPP_JOBS` said, which on a machine with little memory exceeded
+  the bound the key exists to enforce. The backend reads the job count from
+  the plan, and the reclaim of stale `bmi_schedule = "on"` tokens, which ran
+  only under `mcpp build`, runs before the first drive of every build
+  directory (e2e 871).
+- **A pack fills the global dependency cache** with the dependencies its
+  build compiled, as `mcpp build` and `mcpp test` do.
+
+### Changed
+
+- **Every package's BMIs lie below the package's directory, except the root
+  package's.** The rule is the one object files have followed since mcpp#233:
+  `gcm.cache/<package>/<module>.gcm` (`pcm.cache` with clang). A unit that
+  imports a module of another package reads one module map of the modules it
+  reaches through its imports: a mapper file with GCC, and an argument file
+  `@<build directory>/modmap/<package>-<hash>.modmap` of `-fmodule-file=` or
+  `/reference` lines with clang or MSVC. A project whose modules are all its
+  own is laid out, and every command spelled, as before. A package whose
+  module name another package of the graph provides is served from the global
+  dependency cache again; 2026.9.30.2 compiled it in the project.
+- **Every unit of an ELF target that is not freestanding is compiled with
+  `-fPIC`,** whether or not the graph links a shared library, as rustc's
+  default relocation model does on these targets: an object compiled once
+  serves a program and a shared object. Mach-O compilers produce
+  position-independent code by default, PE has no such flag, and nothing
+  changes on those targets or on freestanding ones. The global dependency
+  cache keys these entries by the flag, so each is compiled once more and
+  then served again.
+
 ## [2026.10.1.1] - 2026-10-01
 
 This release implements the plan for member selection, build programs prepared

CHANGELOG.md

@@ -819,7 +819,9 @@ jobs         = "auto"    # or a positive number; --jobs / MCPP_JOBS override it
 bmi_schedule = "off"     # auto (default, = off) | on | off
 ```
 
-`jobs` is how many compiles run at once. `"auto"` is resolved **against the
+`jobs` is how many compiles run at once, in every command that compiles:
+`build`, `run`, `test` and `pack` (2026.10.1.2+; before it, `test` and `pack`
+ran ninja's default number of jobs whatever the key said). `"auto"` is resolved **against the
 machine doing the build**, never frozen into the manifest: it takes the physical
 core count on a heterogeneous CPU (a 13900K is 8 P-cores + 16 E-cores, so its 32
 threads are not 32 equal workers) and clamps that by free memory, because a

docs/04-mcpp-toml.md

@@ -551,14 +551,22 @@ each of them may have its own module of one name.
   are built separately.
 - Two packages that one program links may not provide the same name. The build
   is refused, and the message names the package whose closure holds both.
-- When two packages of one build provide a name, each BMI lies below its
-  package's directory in the build directory, and every compile that may import
-  the name is told which one it means: through a module map with GCC, through
-  `-fmodule-file=` with Clang, and through `/reference` with MSVC. When every
-  name has one provider, the build directory and every command are as they
-  were before.
-- A package that provides such a name is compiled in the project, not served
-  from the global dependency cache.
+- Every package's BMIs lie below the package's directory in the build
+  directory, `gcm.cache/<package>/` (`pcm.cache` with Clang), except the root
+  package's, which lie at their names, as object files do (2026.10.1.2+). A
+  compile that imports a module of another package is told where its BMI is,
+  and where the BMIs of the modules that one imports are, through one module
+  map: a mapper file with GCC (`-fmodule-mapper=`), and an argument file of
+  `-fmodule-file=` lines with Clang or `/reference` lines with MSVC
+  (`@<build directory>/modmap/<package>-<hash>.modmap`). The map lists what the
+  unit reaches through its imports and nothing else, so the command does not
+  change with the rest of the graph. A project whose modules are all its own
+  is laid out, and every command spelled, as before.
+- Until 2026.10.1.2 a BMI moved below its package's directory only when two
+  packages of the graph provided its name, and such a package was not served
+  from the global dependency cache. Both depended on which packages a command
+  selected, so a workspace member was compiled again at each switch between
+  `-p` and `--workspace` (mcpp#751).
 - clangd finds a module by its name in the compilation database, so for a name
   two packages provide it may show the other program's module. The build is
   not affected.

docs/05-dependencies.md

@@ -486,9 +486,17 @@ member that several members use is compiled once.
 - **Selection.** `--workspace`, and a virtual root without `-p`, select every
   member. `-p X`, and a command run in X's directory, plan X and what X
   reaches; `-p X -p Y` plans both together, as one selection (§5.3). The
-  selections share the build directory, so `mcpp build --workspace`
+  selections share the build directory, and a unit is compiled by the same
+  command in every selection that holds it: the command depends on the unit's
+  package, the packages that package reaches, the features the selection
+  activates for it and the declarations a selected member holds as the root,
+  and on nothing else in the graph (2026.10.1.2+). So `mcpp build --workspace`
   followed by `mcpp build -p X` compiles nothing, and a package is compiled
-  again only when its active features differ between the two commands.
+  again only when its active features, or the root declarations of the
+  selected members, differ between the two commands. Before 2026.10.1.2,
+  three facts about the whole graph also reached other members' commands: a
+  module name that two members provide, a file that two members list from
+  outside their own directories, and a member that builds a shared library.
 - **Flags.** A member's `cflags`, `cxxflags`, `ldflags` and defines apply to
   that member's commands. Editing them recompiles that member and what
   imports it; the build directory stays the same.
@@ -570,6 +578,8 @@ myproject/
 └── target/<triple>/<configuration>/
     ├── build.ninja, compile_commands.json  # one graph and one database per configuration
     ├── obj/<package>/                      # intermediate objects of every package
+    ├── gcm.cache/<package>/                # each package's BMIs (pcm.cache with clang)
+    ├── modmap/                             # the module maps of the units that import them
     └── bin/
         ├── server/                         # a member's products: bin/<package name>/
         │   ├── server

docs/07-workspace.md

@@ -170,6 +170,16 @@ relative `-o` keeps meaning the directory the command was typed in.
 take, with the same precedence: `--profile` wins over either, on all three
 commands.
 
+A pack states the build it performs as `mcpp build` states one (mcpp
+2026.10.1.2+): a line for each package that does work, the status row while it
+runs, and `Finished` before the first `Packing` line. A pack over several
+configurations builds every configuration first and writes one `Finished`. The
+second pass of a dispatched `--format` is stated in the same way, and its
+`Distributing` and `Packed` lines follow it. The build runs `[build] jobs`
+compiles at once, as every command that compiles does. Before 2026.10.1.2 the
+build of a pack wrote none of this, and a pack that recompiled for minutes
+showed only `Planning`.
+
 ### Packing several members (mcpp 2026.10.1.1+)
 
 `-p` may be repeated, and `--workspace` and `--exclude` select members as they do

docs/10-pack-and-release.md

@@ -645,7 +645,7 @@ reads this flag**.
 
 | axis | the question | examples | the form of the query |
 |---|---|---|---|
-| **target format** | what kind of image is produced | `-fPIC` (PE code is position independent by design; clang refuses the flag outright) | `triple::parse(...)->is_pe()`, host fallback |
+| **target format** | what kind of image is produced | `-fPIC`: on every unit of an ELF target that is not freestanding, whether or not the graph links a shared library (2026.10.1.2+), and never on PE, whose code is position independent by design and where clang refuses the flag outright | `triple::parse(...)->object_format()`, `is_pe()`, host fallback |
 | **target ABI** | which linker will consume this | `--out-implib` vs `/IMPLIB:`, `/DEF:`, the SONAME / install-name form | `is_msvc_target(tc)`, `triple->is_msvc_env()` |
 | **dialect** | which program mcpp is invoking | `-L` vs `/LIBPATH:`, `-I` vs `/I`, the archive command | `dialect_for(tc)`, `LinkStyle::SeparateLinker` |
 

docs/91-toolchain-internals.md

@@ -126,13 +126,17 @@ mcpp 输出的 S1 文档满足 S1 等级 2,不输出 `ide.options`。等级 3 
   真的编译就能得到(§3.4)。`ide.toolchains.<id>.build-id` 给出编译器的构建标识,
   取自 mcpp 已经算出的驱动身份(工具链指纹的同一个字段),同一工具链的两次运行
   之间保持稳定。**已实现**
-- **R3.8a** 一个模块名在一个程序之内标识一个模块,而一个配置可以包含多个程序。同一
-  配置中两个包提供同一个模块名时(两者不在同一个包的闭包中,#732),两个单元的
-  `provides` 都列出这个名字;可能导入它的每个单元,其 `arguments` 带有构建所用的
-  绑定:GCC 为 `-fmodule-mapper=<映射文件>`(相对 `work-directory`),Clang 为
-  `-fmodule-file=<名字>=<路径>`,MSVC 为 `/reference <名字>=<路径>`。只按名字在文档中
-  查找提供方的消费方,因此可能取到另一个程序的模块;构建本身不受影响。每个名字只有
-  一个提供方时,文档与此前逐字相同。**已实现**
+- **R3.8a** 一个模块名在一个程序之内标识一个模块,而一个配置可以包含多个程序
+  (#732)。除根包之外,每个包的 BMI 都位于其所属包的子目录下(2026.10.1.2+,#751)。
+  导入其他包模块的单元,以及提供这样一个模块的单元,其 `arguments` 带有构建所用的
+  一份模块映射:GCC 为 `-fmodule-mapper=<映射文件>`(相对 `work-directory`),Clang
+  与 MSVC 为一个参数文件 `@<绝对路径>/modmap/<包>-<哈希>.modmap`,其中每行一个
+  `-fmodule-file=<名字>=<路径>` 或 `/reference <名字>=<路径>`。映射只列出该单元经其
+  导入所能到达的模块,因此同一单元在一个配置的每一种成员选择下,`arguments` 逐字相同。
+  `.modmap` 后缀与 CMake 模块映射相同,读者可据此把未展开的参数文件识别为模块机制。
+  同一个名字由两个包提供时,两个单元的 `provides` 都列出它;只按名字在文档中查找提供方
+  的消费方,因此可能取到另一个程序的模块,构建本身不受影响。模块全部属于根包的工程,
+  文档与此前逐字相同。**已实现**
 - **R3.9** `ide.role` 取自扫描器读到的模块声明形式:
 
   | 声明 | `ide.role` |

docs/specs/build-database.md

@@ -778,7 +778,9 @@ jobs         = "auto"    # or a positive number; --jobs / MCPP_JOBS override it
 bmi_schedule = "off"     # auto (default, = off) | on | off
 ```
 
-`jobs` 是同时运行多少个编译。`"auto"` 是**相对正在执行构建的这台机器**
+`jobs` 是同时运行多少个编译，适用于每一条会编译的命令：`build`、`run`、`test` 与 `pack`
+（2026.10.1.2+；此前 `test` 与 `pack` 无论这个键怎么写都按 ninja 的默认并行数运行）。
+`"auto"` 是**相对正在执行构建的这台机器**
 解析的，绝不会被冻结进 manifest：它取一颗异构 CPU 的物理核心数（一颗
 13900K 是 8 个 P-core + 16 个 E-core，所以它的 32 个线程不是 32 个
 等价的工作者），并按空闲内存夹紧这个数字，因为单次模块接口编译峰值