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release: 2026.10.26.1 -- the control contract, concurrency, one C++ runtime per process (#838, #839) - #841

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release: 2026.10.26.1 -- the control contract, concurrency, one C++ runtime per process (#838, #839)#841
Sunrisepeak merged 16 commits into
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release/2026.10.26.1

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@Sunrisepeak Sunrisepeak commented Oct 25, 2026

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Release 2026.10.26.1 — the control contract, concurrency, and one C++ runtime per process. Fixes #838 and #839. Design: .agents/docs/2026-10-26-control-contract-runtime-and-ide-ecosystem-design.md (rev 4 records what changed during implementation). Probe PR #840 settled O5, O8 and O10 on real runners.

What changes

Concurrency (#839, SPEC-011)

  • Each build directory has a lock (.mcpp-build.lock with an owner record). It is taken once the configuration's fingerprint names the directory and held until ninja finishes.
  • A second build of the same configuration waits. It reports the holder (Waiting for the build directory, held by pid N (cmd, from client, Ns)) and emits a waiting event.
  • run releases the lock before exec. test holds it until its tests finish.
  • Link outputs are published whole (D22):
    • POSIX: link to $out.tmp, then mv -f.
    • Windows host: mcpp link-output renames the old file aside first.
  • target/.build_cache and mcpp.lock are replaced atomically.
  • mcpp.lock is written optimistically: a lock another run wrote meanwhile is not overwritten ([lockfile-concurrent]).
  • On SIGINT, SIGTERM or SIGHUP the build stops what it started, leaves its record cancelled, and dies of the signal (exit 128+N).

The control contract (docs/50 §9–§13, docs/52)

  • mcpp build --message-format json streams NDJSON events (plan, waiting, progress, diagnostic, artifact) and ends with a one-line mcpp.build envelope.
  • Every build writes a result record, result.json, plus target/.last-result.json. The record holds the artifacts with their launch descriptors and the compiler diagnostics with path and range.
  • mcpp run --print-launch prints the launch descriptor instead of running.
  • --deny <effects> and MCPP_DENY_EFFECTS: a run stops before a denied effect and exits 5. --offline counts as --deny network.
  • Global --home.
  • New query surfaces:
    • search --format json (mcpp.search)
    • index list --format json (mcpp.index)
    • pack --list-formats (mcpp.pack.formats)
  • Colour on a pipe via CLICOLOR_FORCE / FORCE_COLOR.
  • MCPP_CLIENT names the caller in the lock owner and in the result record.
  • A manifest rejection is located at the key it names, and envelope diagnostics carry path and range.
  • Next-step lines now read help:.

One C++ runtime per process (#838, SPEC-002 §7)

  • Three modes: U (unified), I (island) and H (host decides).
  • A foreign runtime is placed after the program's own on the link line.
  • A foreign runtime is recognised by type (named on the link line, or through DT_NEEDED). The old substring sniff is gone.
  • An island is declared with requires = [{ layer = "mcpp:c++-abi=libstdc++", visibility = "private" }] (also under [target.<sel>]). It is verified after the link ([cxx-runtime-collision]) and refused beside a C++ shared library ([cxx-runtime-island]).
  • A graph-supplied libstdc++ works under clang (gcc.libstdcxx). Build programs see MCPP_CXX_STDLIB and MCPP_CXX_ABI_ROOT.
  • abi: capabilities are read as requires (COMPAT abi-capability).

Other

  • The root compile_commands.json is written only when asked for. Precedence: MCPP_COMPILE_COMMANDS, then [build] compile_commands, then the config.toml default.
  • cache list reads each entry's recorded footprint.
  • Compiler probe and provider handshake answers are cached under the home.

Tests

  • New e2e tests 933–939. 933, 934 and 936–939 fail on 2026.10.24.1 and pass here; 935 depends on timing (B is reported when observed).
  • Unit suite: 151 tests pass locally. Every check_* script that runs on Linux passes, and git diff --check is clean.
  • Measured locally with xlings 2026.10.26.1: emit build-database 71 ms, toolchain list 44 ms, build with no changes 50 ms.

Ecosystem

Sunrisepeak and others added 16 commits October 26, 2026 04:14
@Sunrisepeak @speak-agent
feat: the build directory's lock, atomic link outputs, the result rec…
ea1fd4b 
…ord and the control contract

- mcpp.build.dirlock: one lock per build directory, taken when the finish
  phase starts writing it and held through ninja; fast paths take it around
  ninja; run releases it before the program starts; waiters see the holder
  (pid, command, MCPP_CLIENT, age). Fixes #839.
- Link outputs are published whole: POSIX links write $out.tmp and rename;
  a Windows host moves the old artifact aside (mcpp link-output).
- target/.build_cache: read-modify-write under its own lock, atomic replace.
- mcpp.build.result: result.json (running/ok/failed), target/.last-result.json,
  artifacts with launch descriptors, compiler diagnostics.
- mcpp build --message-format json: NDJSON events (plan, waiting, progress,
  diagnostic, artifact) and the mcpp.build envelope.
- mcpp run --print-launch: the mcpp.launch envelope.
- --deny / MCPP_DENY_EFFECTS; --offline is --deny network; a run stopped
  before a denied effect exits 5.
- --home <dir>: this run's home (MCPP_HOME for one process).

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
feat: query surfaces, colour conventions, the opt-in root compile dat…
ba13014 
…abase, a cheaper cache listing

- search --format json (mcpp.search; no keyword lists the catalogue, each index
  read once by declared identity), index list --format json (mcpp.index),
  pack --list-formats (mcpp.pack.formats); --protocol-version lists them.
- CLICOLOR_FORCE / FORCE_COLOR force colour; NO_COLOR / MCPP_NO_COLOR win.
- [build] compile_commands (config.toml default, MCPP_COMPILE_COMMANDS
  override): the project-root copy of the compile database is published only
  where asked; a copy an earlier mcpp left is named once. The configuration
  record carries the location for the fast path. e2e tests that read the root
  copy opt in.
- Cache entries record their footprint when written; cache list reads it.
- A failed provisioning reports xlings' diagnostic without suggesting the
  same install by hand.

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
feat: one C++ runtime per process; a graph-supplied libstdc++ under c…
694a91b 
…lang; verified islands

- A package that provides mcpp:c++-abi=libstdc++ serves an llvm build: the
  link takes the libstdc++ cells with -stdlib=libstdc++ --unwindlib=libgcc
  (compiler-rt stays); a std module whose source clang does not know by its
  extension (libstdc++'s bits/std.cc) is precompiled as a module.
- requires takes { layer, visibility }: visibility = "private" (c++-abi only,
  requires-private-layer otherwise) declares an island; [target.<sel>]
  requires unions in like requires_abi.
- The island: declared, named on the link line, or needed by a library the
  line names (DT_NEEDED). Refused when the build also links a C++ shared
  library [cxx-runtime-island]; the other runtime's words follow the build's
  own runtime on the line (mcpp#838); every C++ image is verified after the
  link [cxx-runtime-collision]: no layout-dependent references from island
  objects, no ABI-layer imports at the other runtime's versions, no typeinfo
  shared with an image built on it.
- The ldflags substring sniff for stdc++ is gone.
- abi: capabilities read the resolved target side (COMPAT abi-capability);
  an undeclared island is the COMPAT reading undeclared-cxx-runtime.

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
test: the build directory lock, the control contract, the opt-in root…
17bca6c 
… database, whole link outputs

935-938 fail on 2026.10.24.1 (935 by chance: the race is timing-dependent).
The failed build's raw ninja output reaches the result record, and the
mcpp.build envelope is one line of the NDJSON stream.

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
perf: a compiler's query answers and the provider handshake are cache…
7dacd4f 
…d under the home

Keyed by the command and the size and mtime of the files it names (the
compiler), and by the xlings binary's path, size and mtime. With xlings
2026.10.26.1: emit build-database 604 -> 71 ms, toolchain list 554 -> 44 ms,
a build with nothing to do 50 ms.

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
feat: an interrupted build leaves its record cancelled; mcpp.lock is …
ed3af1d 
…written optimistically; a diagnostic carries the location its message names

A signal that ends a build while it writes its directory leaves result.json and
target/.last-result.json as cancelled: the interrupted form is rendered when the
run starts, and the handler writes it with open/write/rename after it has
stopped the guarded groups (POSIX status 128+N; Windows: the console handler).

mcpp.lock is compared, before it is written, with what the run read when it
started; a lock another run wrote meanwhile is not overwritten
([lockfile-concurrent], help: run the command again). It is replaced
atomically; a linked lock is written through its link, and a read-only one is
refused as before.

A manifest's rejection is located at the key or table it names, and an
envelope's diagnostic takes path and range from a message that begins with a
location. mcpp build and mcpp pack under --message-format json carry mcpp's
own errors as diagnostics.

The function-size and Unicode-path checks read the configuration's compile
database when the project asks for no root copy.

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
feat: build programs see the graph's C++ library; a next step reads h…
af8017f 
…elp:

A build program reads MCPP_CXX_STDLIB as the graph's c++-abi supplier says, and
MCPP_CXX_ABI_ROOT (mcpp::cxx_abi_root()) names that package's root, so a rule
that drives a second compiler -- the SYCL device compiler -- points it at the
same C++ library. Read from the declarations, because build programs run before
the target side is resolved.

mcpp's next-step lines read help: (they read hint:), one convention with the
diagnostics' help lines (SPEC-012).

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
docs: the control contract, concurrency, one C++ runtime per process,…
8e0f804 
… and driving mcpp from a program

docs/50 gains the build stream, the result record, the launch descriptor,
--deny, the queries and the caller's name; docs/52 states how a program or an
agent drives mcpp. New specifications: SPEC-011 (concurrent runs) and SPEC-012
(output for people). SPEC-002 v1.3 (requires as a table, one C++ runtime per
process), SPEC-003 v1.2 (exit 5 and signals), SPEC-010 v0.2 (--home). docs/22
and docs/42 describe the runtime modes and SYCL on libstdc++; docs/04 the
[build] compile_commands key. The design record gains revision 4.

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
release: 2026.10.26.1
06b1ead 
Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
fix: the lock's backoff compiles beside <windows.h>
271d2ac 
<windows.h> defines min as a macro; std::min is parenthesised.

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
fix: one process holds a build directory once; a cold home is not cre…
09513c2 
…ated by a cache

`mcpp run --format <f>` builds the program and then packs it, and the pack
plans the same configuration: the second acquisition of the directory's lock
waited for the first, in the same process (flock and LockFileEx lock per open
file). The lock is now shared by every holder in the process.

The compiler-probe and provider-handshake caches are written only in a home that
exists, so an offline `self doctor` of a cold home leaves none behind (e2e 604
on Windows, where the doctor probes MSVC).

The function-size check points clang-tidy at the directory of the database it
read; e2e 936 compares a launch's program with its artifact as paths.

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
fix: a query leaves the home as it found it; the left root database i…
a481984 
…s recognised on Windows

The compiler-probe and provider-handshake answers are written only by a run
that writes the global cache -- one that plans or builds, and was not denied
write-global-cache -- and read by every command. `self doctor`, `self env`
and `toolchain list` declare no such effect, and an online doctor changed the
home (e2e 920 on Windows).

The note about a root compile_commands.json an earlier mcpp left compares the
file's directories in one spelling, so a Windows file (escaped backslashes, a
drive letter in either case) is recognised (e2e 937).

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
release: bundle xlings 2026.10.26.1
6e15d51 
The vendored floor and every CI pin move to xlings 2026.10.26.1
(openxlings/xlings#707).

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
test: the launch's program is compared as a path; 937 edits the manif…
2cbad5e 
…est without sed -i

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
test: 936 E reads the selected home by its name, which Windows spells…
f1b5d50 
… its own way

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak @speak-agent
test: 936 H is POSIX: a shell's kill ends a native Windows process ou…
91dd1ff 
…tright

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
@Sunrisepeak
Sunrisepeak merged commit 434b3fb into main Oct 26, 2026
76 checks passed
This was referenced Oct 26, 2026
Merged
Merged
Sunrisepeak pushed a commit to openxlings/xim-pkgindex that referenced this pull request Oct 26, 2026
@github-actions @speak-agent
bump(mcpp): track 2026.10.26.1 as latest (#1082)
4dc7e05 
mcpp 2026.10.26.1 (mcpp-community/mcpp#841); payload sha256 checked against the GitHub and GitCode .sha256 sidecars.

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>
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关于使用sycl进行异构编程时输出c++运行时差异导致的异常不匹配问题。

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@Sunrisepeak