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) (#754)

Implements .agents/docs/2026-10-01-pack-drive-and-selection-independent-compile-design.md and resolves #751 and #753.

- 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 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 have since #233; a unit reads one module map of what it reaches
  through its imports (a GCC mapper, a clang argument file of -fmodule-file=
  lines, an MSVC command file of /reference lines).
- 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.

Verification: CI on 71d09f0 (42 passed; the two xcode-27 jobs fail as on
main, #669). GalTranslPP built with mcpp from this branch on windows-2025,
run 36814777279 on the final head: mcpp run -p GPPCLI after
build --workspace took 10 s (3m22s on 2026.9.30.2), both release packs 89 s.

Author: speak-agent

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

@@ -0,0 +1,184 @@
+#!/usr/bin/env bash
+# Sandbox verification of the release that implements
+# .agents/docs/2026-10-01-pack-drive-and-selection-independent-compile-design.md
+# (#751, #753), run against the PUBLISHED release inside an xlings sandbox:
+#
+#   B64=$(base64 -w0 .agents/docs/2026-10-01-pack-drive-and-selection-verify.sh)
+#   xlings subos new v1002 2>/dev/null || true
+#   xlings subos use v1002 --sandbox --cmd "echo $B64 | base64 -d > /tmp/v.sh && VER=<version> bash /tmp/v.sh"
+#
+# VER selects the release under test. Running it with VER=2026.10.1.1 is the
+# control: every section marked CHANGE must fail there, and every other
+# section must pass on both.
+#
+# Every probe directory is removed at the start of its section, because the
+# sandbox's $HOME persists between runs of the same subos. A section that does
+# not run is reported as SKIP and counted apart from a pass.
+set -u
+VER="${VER:?VER=<version under test>}"
+W="${W:-$HOME/v1002}"
+fails=0; passes=0; skips=0
+pass() { echo "PASS  $1"; passes=$((passes+1)); }
+fail() { echo "FAIL  $1"; [ -n "${2:-}" ] && [ -f "$2" ] && tail -20 "$2"; fails=$((fails+1)); }
+skip() { echo "SKIP  $1"; skips=$((skips+1)); }
+
+# 0. The release under test, from the published channel, with the CN mirror.
+if [ -n "${MCPP_OVERRIDE:-}" ]; then
+    MCPP="$MCPP_OVERRIDE"
+else
+    xlings config --mirror CN >/dev/null 2>&1 || true
+    xlings update >/dev/null 2>&1 || true
+    xlings install "mcpp@$VER" -y > /tmp/v1002-install.log 2>&1 || true
+    MCPP="$HOME/.xlings/data/xpkgs/xim-x-mcpp/$VER/bin/mcpp"
+fi
+if [ ! -x "$MCPP" ]; then
+    echo "FATAL: mcpp $VER is not installable from the index"; tail -20 /tmp/v1002-install.log; exit 2
+fi
+got=$("$MCPP" --version 2>&1 | head -1)
+case "$got" in *"$VER"*) pass "0 installed: $got";; *) fail "0 version: $got";; esac
+[ -n "${MCPP_OVERRIDE:-}" ] || "$MCPP" self config --mirror CN >/dev/null 2>&1 || true
+mkdir -p "$W"
+
+# compiles_after <log> <lines>: the compile steps `.ninja_log` records after
+# its first <lines> lines.
+compiles_after() {
+    tail -n +"$(( $2 + 1 ))" "$1" | awk -F'\t' '$4 ~ /\.(o|obj)$/ { n++ } END { print n + 0 }'
+}
+# no_compile <label> <selection...>: the build of the selection compiles nothing.
+no_compile() {
+    local label="$1"; shift
+    local log before n
+    log=$(find target -name .ninja_log | head -1)
+    before=$(wc -l < "$log")
+    "$MCPP" build "$@" > nc.log 2>&1 || { fail "$label: build $* failed" nc.log; return 1; }
+    n=$(compiles_after "$log" "$before")
+    [ "$n" = 0 ] || { fail "$label: build $* compiled $n units" nc.log; return 1; }
+    return 0
+}
+member() {   # <dir> <name> <kind> [<dependency path>]
+    mkdir -p "$1/src"
+    {
+        printf '[package]\nname = "%s"\nversion = "0.1.0"\n' "$2"
+        [ -n "${4:-}" ] && printf '\n[dependencies]\ncore = { path = "%s" }\n' "$4"
+        printf '\n[targets.%s]\nkind = "%s"\n' "$2" "$3"
+        [ "$3" = bin ] && printf 'main = "src/main.cpp"\n'
+    } > "$1/mcpp.toml"
+}
+
+# 1. CHANGE (#751, GalTranslPP's shape): two members compile one file from
+# outside their directories; after --workspace, no selection compiles again.
+rm -rf "$W/s1"; mkdir -p "$W/s1/shared"; cd "$W/s1"
+printf '[workspace]\nmembers = ["core", "app", "tool"]\n' > mcpp.toml
+printf 'export module m;\nexport int answer() { return 42; }\n' > shared/m.cppm
+member core core lib; member app app bin ../core; member tool tool bin
+printf '\n[build]\nsources = ["src/*.cppm", "../shared/m.cppm"]\n' >> core/mcpp.toml
+printf '\n[build]\nsources = ["src/*.cpp", "../shared/m.cppm"]\n' >> tool/mcpp.toml
+printf 'export module corelib;\nimport m;\nexport int core_value() { return answer(); }\n' > core/src/core.cppm
+printf '#include <cstdio>\nimport corelib;\nint main() { std::printf("%%d\\n", core_value()); }\n' > app/src/main.cpp
+printf '#include <cstdio>\nimport m;\nint main() { std::printf("%%d\\n", answer() + 1); }\n' > tool/src/main.cpp
+if "$MCPP" build --workspace > s1.log 2>&1; then
+    if no_compile "1" -p app && no_compile "1" -p tool && no_compile "1" --workspace && no_compile "1" -p app; then
+        pass "1 CHANGE: a file two members list is compiled once for every selection"
+    fi
+else fail "1 the workspace did not build" s1.log; fi
+
+# 2. CHANGE: two members each with their own module `m`; alternating
+# selections compile nothing once each was built, and each program prints its
+# own value.
+rm -rf "$W/s2"; mkdir -p "$W/s2"; cd "$W/s2"
+printf '[workspace]\nmembers = ["core", "app", "tool"]\n' > mcpp.toml
+member core core lib; member app app bin ../core; member tool tool bin
+printf 'export module m;\nexport int answer() { return 42; }\n' > core/src/m.cppm
+printf 'export module corelib;\nimport m;\nexport int core_value() { return answer(); }\n' > core/src/core.cppm
+printf '#include <cstdio>\nimport corelib;\nint main() { std::printf("%%d\\n", core_value()); }\n' > app/src/main.cpp
+printf 'export module m;\nexport int answer() { return 7; }\n' > tool/src/m.cppm
+printf '#include <cstdio>\nimport m;\nint main() { std::printf("%%d\\n", answer()); }\n' > tool/src/main.cpp
+if "$MCPP" build --workspace > s2.log 2>&1; then
+    a=$(find target -path '*/bin/app/app' -type f | head -1); t=$(find target -path '*/bin/tool/tool' -type f | head -1)
+    if [ "$("$a")" = 42 ] && [ "$("$t")" = 7 ] \
+       && no_compile "2" -p app && no_compile "2" -p tool && no_compile "2" -p app && no_compile "2" --workspace; then
+        pass "2 CHANGE: two modules of one name, no recompile across selections, each program its own value"
+    fi
+else fail "2 the workspace did not build" s2.log; fi
+
+# 3. CHANGE: a member that builds a shared library does not change the other
+# members' commands.
+rm -rf "$W/s3"; mkdir -p "$W/s3"; cd "$W/s3"
+printf '[workspace]\nmembers = ["core", "app", "dso"]\n' > mcpp.toml
+member core core lib; member app app bin ../core; member dso dso shared
+printf 'export module corelib;\nexport int core_value() { return 3; }\n' > core/src/core.cppm
+printf 'import corelib;\nint main() { return core_value() == 3 ? 0 : 1; }\n' > app/src/main.cpp
+printf 'export module dsolib;\nexport int dso_value() { return 5; }\n' > dso/src/dso.cppm
+if "$MCPP" build --workspace > s3.log 2>&1; then
+    if no_compile "3" -p app && no_compile "3" --workspace; then
+        pass "3 CHANGE: a shared-library member leaves the other members' commands alone"
+    fi
+else fail "3 the workspace did not build" s3.log; fi
+
+# 4. CHANGE (#753): a pack states its build, and Finished precedes Packing.
+rm -rf "$W/s4"; mkdir -p "$W/s4"; cd "$W/s4"
+member . p4 bin
+printf 'int main() { return 0; }\n' > src/main.cpp
+if "$MCPP" pack --format tar > s4.log 2>&1; then
+    fin=$(grep -n 'Finished' s4.log | head -1 | cut -d: -f1); pk=$(grep -n 'Packing' s4.log | head -1 | cut -d: -f1)
+    if grep -q 'Compiling p4' s4.log && [ -n "$fin" ] && [ -n "$pk" ] && [ "$fin" -lt "$pk" ]; then
+        pass "4 CHANGE: the pack states its build, Finished before Packing"
+    else fail "4 CHANGE: the pack's build is not stated" s4.log; fi
+else fail "4 the pack failed" s4.log; fi
+
+# 5. CHANGE: `[build] jobs = 1` bounds mcpp test's compiles.
+rm -rf "$W/s5"; mkdir -p "$W/s5"; cd "$W/s5"
+member . p5 bin
+printf '\n[build]\njobs = 1\n' >> mcpp.toml
+mkdir -p tests
+for i in 1 2 3 4; do
+    printf 'constexpr unsigned long long s%s() { unsigned long long x = %s; for (unsigned k = 0; k < 600; ++k) for (unsigned j = 0; j < 600; ++j) x = x * 6364136223846793005ull + 1; return x; }\nunsigned long long v%s() { constexpr auto v = s%s(); return v; }\n' $i $i $i $i > src/u$i.cpp
+done
+printf 'int main() { return 0; }\n' > src/main.cpp
+printf 'int main() { return 0; }\n' > tests/t.cpp
+if "$MCPP" test > s5.log 2>&1; then
+    log=$(find target -name .ninja_log | head -1)
+    if awk -F'\t' 'NR > 1 && $4 ~ /\.o$/ { s[n] = $1; e[n] = $2; n++ }
+                   END { for (i = 0; i < n; i++) for (j = i + 1; j < n; j++) if (s[i] < e[j] && s[j] < e[i]) exit 1; exit (n < 4) }' "$log"; then
+        pass "5 CHANGE: mcpp test runs one compile at a time under jobs = 1"
+    else fail "5 CHANGE: mcpp test overlapped compiles under jobs = 1" "$log"; fi
+else fail "5 mcpp test failed" s5.log; fi
+
+# 6. Index packages that provide modules build, run, and are served from the
+# global cache by a second project, their BMIs below their packages' directories.
+for d in s6a s6b; do
+    rm -rf "$W/$d"; mkdir -p "$W/$d/src"
+    printf '[package]\nname = "eco"\nversion = "0.1.0"\n\n[dependencies]\n"compat.zlib" = "*"\n"mcpplibs.cmdline" = "*"\n\n[targets.eco]\nkind = "bin"\nmain = "src/main.cpp"\n' > "$W/$d/mcpp.toml"
+    cat > "$W/$d/src/main.cpp" <<'EOF'
+#include <cstdio>
+#include <zlib.h>
+import mcpplibs.cmdline;
+int main() { std::printf("zlib %s\n", zlibVersion()); return 0; }
+EOF
+done
+cd "$W/s6a"
+if "$MCPP" run > s6a.log 2>&1 && grep -q '^zlib ' s6a.log; then
+    cd "$W/s6b"
+    if "$MCPP" run > s6b.log 2>&1 && grep -q '^zlib ' s6b.log && grep -q 'Cached mcpplibs.cmdline' s6b.log; then
+        pass "6a index packages build, run, and are served from the cache"
+        if [ -n "$(find target -path '*.cache/*cmdline*/*' -type f | head -1)" ]; then
+            pass "6b CHANGE: a cached dependency's BMIs are staged below its package's directory"
+        else fail "6b CHANGE: the cached BMIs are staged at their names" s6b.log; fi
+    else fail "6a the second project was not served from the cache" s6b.log; fi
+else fail "6 index packages" s6a.log; fi
+
+# 7. xlings, built from its source with the release under test.
+rm -rf "$W/s7"; mkdir -p "$W/s7"; cd "$W/s7"
+if git clone -q --depth 1 https://github.com/openxlings/xlings.git xlings > s7-clone.log 2>&1 \
+   || git clone -q --depth 1 https://gitee.com/openxlings/xlings.git xlings > s7-clone.log 2>&1; then
+    cd xlings
+    if "$MCPP" build > s7.log 2>&1; then
+        x=$(find target -path '*/bin/xlings' -type f | head -1)
+        if [ -n "$x" ] && "$x" --version > s7v.log 2>&1; then
+            if no_compile "7" ; then pass "7 xlings builds with the release, runs, and a second build compiles nothing: $(head -1 s7v.log)"; fi
+        else fail "7 the xlings that was built does not run" s7v.log; fi
+    else fail "7 xlings does not build" s7.log; fi
+else skip "7 xlings could not be cloned"; fi
+
+echo "---- $passes passed, $fails failed, $skips skipped"
+[ "$fails" = 0 ]

.agents/docs/2026-10-01-pack-drive-and-selection-verify.sh

@@ -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.