feat(toolchain): backend abstraction (CommandDialect) + MinGW-w64 via the xlings ecosystem — 0.0.89#211
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…Part A) New mcpp.toolchain.dialect: command-line *spellings* (gnu vs msvc) as a value-type traits table — flags.cppm and ninja rule templates now spell -I/-D/-std=/-c/-o/-O/-g/ar-invocations through it instead of hardcoding GNU syntax. BmiTraits gains the module-flag spellings (compileModulesFlag, stdBmiUsePrefix, moduleOutputPrefix, bmiSearchPrefix), replacing the is_clang()/stdlib_id branches in flags.cppm. ProviderCapabilities gains has_builtin_p1689_scan (drops ninja_backend's is_gcc gate). Toolchain gains envOverrides (EnvVar list — std::pair member trips GCC-16 module pendings) merged into ninja's child env; the MSVC backend will carry INCLUDE/LIB/PATH through it. gcc::std_module_build_commands normalizes the provider surface to the command-sequence shape clang already has. resolve_link_model returns the empty PE model explicitly on Windows. Zero-diff verified: build.ninja byte-identical (modulo the mcpp self-path var) for GCC and LLVM toolchains on a multi-module import-std project; mcpp test 31/31.
…) (0.0.89) User-facing 'mingw' spec → xim:mingw-gcc (winlibs GCC 16.1.0 + MinGW-w64 14.0.0 UCRT standalone build, mirrored at xlings-res/mingw-gcc). Reuses the GCC backend end-to-end (gcm module pipeline, bits/std.cc import std); Windows adds static libstdc++/libgcc defaults so produced exes run standalone, and -static under linkage="static". archive_tool resolves the bundled ar.exe; std.cc lookup gains a version-dir scan fallback. Fixes ridden along: toolchain list 'Available' + partial-version resolution read xpkg versions for the HOST platform (was hardcoded linux — empty on win/mac); toolchain install no longer pulls glibc/linux-headers on win/mac. e2e 97 (requires: windows cap) + ci-windows MinGW step + unit tests (dialect rows, mingw spec mapping); docs + CHANGELOG; version 0.0.89.
The Windows-host if-constexpr broke the linkmodel contract tests on Windows CI (they resolve synthetic Linux-shaped toolchains anywhere). Target-keyed is also the semantics a future cross build needs.
std::vprint_unicode's __open_terminal/__write_to_terminal live in libstdc++exp.a on Windows-GCC targets — first real MinGW link on CI failed with undefined references from bits/print.h.
winlibs POSIX-threads libstdc++ otherwise leaves produced exes depending on libwinpthread-1.dll — the standalone-exe e2e caught it (empty output, missing-DLL abort). -Wl,-Bstatic -lwinpthread -Wl,-Bdynamic is the standard recipe; libwinpthread.a ships in the payload.
The silent standalone-run failure gave nothing to debug — inspect DLL imports directly and dump them on any failure.
…cipe loses to driver implicit libs CI import table still showed libwinpthread-1.dll after -Wl,-Bstatic -lwinpthread; winlibs' documented answer for standalone exes is a full -static link (system DLLs still resolve via import libs). Gated on staticStdlib so [build] static_stdlib=false opts out.
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Summary
Implements Parts A + B of
.agents/docs/2026-07-13-toolchain-backend-abstraction-msvc-mingw-design.md(companion audit:2026-07-13-compiler-dialect-touchpoint-audit.md) in one PR, per plan. Part C (native MSVC cl.exe build backend) is the next round and builds on A.Part A — toolchain backend abstraction (zero behavior change)
mcpp.toolchain.dialect: command-line spellings as a value-traits table (gnushared by GCC/Clang/MinGW;msvcrow ready for the cl.exe backend). flags.cppm + ninja rule templates now spell-I/-D/-std=/-c/-o/-O/-gand the archive command through it.BmiTraitsgains module-flag spellings — flags.cppm'sis_clangmodule branches are now data-driven.ProviderCapabilities.has_builtin_p1689_scanreplaces ninja_backend'sis_gccscanner gate.Toolchain::envOverrides(EnvVar list → ninja child env): the seam for the MSVC backend's INCLUDE/LIB/PATH.gcc::std_module_build_commandsnormalizes the provider surface (command-sequence shape, same as clang).resolve_link_model: explicit empty PE model, keyed on the target (msvc/mingw triples).Part B — MinGW-w64 GCC via the xlings ecosystem
mcpp toolchain install mingw 16.1.0/default mingw@16.1.0→ xim:mingw-gcc (winlibs GCC 16.1.0 + MinGW-w64 14.0.0 UCRT standalone, mirrored at xlings-res/mingw-gcc — GitHub + GitCode, GET-verified 200/284579900 both ends; index: openxlings/xim-pkgindex#382, merged).-staticlink (winlibs' documented recipe — CI import tables proved the piecemeal recipe loses to driver implicit libs) +-lstdc++exp(std::print's __open_terminal); opt-out[build] static_stdlib=false.Verified on Windows CI (temp PR #209, green run 29233042340)
Version
0.0.89 (mcpp.toml + fingerprint.cppm + CHANGELOG).