feat(toolchain): backend abstraction (CommandDialect) + MinGW-w64 via the xlings ecosystem — 0.0.89 (#211)

* refactor(toolchain): CommandDialect + backend surface normalization (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.

* feat(toolchain): MinGW-w64 GCC via the xlings ecosystem (mingw@16.1.0) (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.

* fix(linkmodel): key the PE early-out on the target, not the host

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.

* fix(flags): MinGW links libstdc++exp for std::print terminal symbols

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.

* fix(flags): force winpthread static on MinGW links

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.

* test(e2e): 97 asserts the exe import table (objdump) + diagnostic output

The silent standalone-run failure gave nothing to debug — inspect DLL
imports directly and dump them on any failure.

* fix(flags): MinGW default links -static — the piecemeal winpthread recipe 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.

Author: Sunrisepeak

.github/workflows/ci-windows.yml

@@ -220,6 +220,16 @@ jobs:
           cd hello_win
           "$MCPP_SELF" run
 
+      # MinGW-w64 GCC via the xlings ecosystem (xim:mingw-gcc → xlings-res
+      # winlibs mirror): install → default → modules build/run → standalone
+      # exe. Same flow as e2e 97 but as a visible CI step. Payload is cached
+      # via the mcpp sandbox cache after the first run.
+      - name: "Toolchain: MinGW — install → build → run (xim:mingw-gcc)"
+        shell: bash
+        run: |
+          export MCPP_VENDORED_XLINGS="$XLINGS_BIN"
+          MCPP="$MCPP_SELF" bash tests/e2e/97_mingw_toolchain.sh
+
       # windows-latest ships VS 2022 Enterprise with the VC workload, so
       # msvc@system detection MUST succeed here — a failure is a regression
       # in the discovery/identification chain (vswhere → env → paths).

CHANGELOG.md

@@ -3,6 +3,36 @@
 > 本文件追踪 `mcpp-community/mcpp` 公开仓的版本演进。
 > 格式参考 [Keep a Changelog](https://keepachangelog.com/zh-CN/1.1.0/)。
 
+## [0.0.89] — 2026-07-13
+
+### 新增
+
+- **MinGW-w64 工具链入 xlings 生态(Windows 原生 GCC,无需 Visual Studio)**。
+  `mcpp toolchain install mingw 16.1.0` / `default mingw@16.1.0`:xim 包
+  `mingw-gcc`(winlibs GCC 16.1.0 + MinGW-w64 14.0.0 UCRT 独立构建,镜像于
+  xlings-res/mingw-gcc,GitHub+GitCode 双端)。复用既有 GCC 后端
+  (gcm 模块管线、libstdc++ `bits/std.cc` 的 `import std`);Windows 上
+  libstdc++/libgcc 默认静态链接(产物免带 DLL,`[build] static_stdlib=false`
+  可关),`linkage="static"` 升级全静态。e2e 97 覆盖 install→default→
+  多模块 build/run→独立 exe 验证;ci-windows 新增专项步骤。
+  连带修复:`toolchain list` 的 Available 段与部分版本解析此前硬编码按
+  "linux" 平台读取 xpkg 版本(Windows/macOS 上恒空);`toolchain install`
+  在 Windows/macOS 不再错误安装 glibc/linux-headers 依赖。
+
+### 重构
+
+- **工具链后端抽象层(Part A,对 GCC/Clang 零行为变化,build.ninja 零 diff
+  实证)**。新增 `mcpp.toolchain.dialect`(命令行拼写 traits:gnu/msvc 两行
+  数据,`-I/-D/-std=/-c/-o/-O/-g/ar` 及归档命令模板经其发射);`BmiTraits`
+  并入模块旗标拼写(`compileModulesFlag`/`stdBmiUsePrefix`/
+  `moduleOutputPrefix`/`bmiSearchPrefix`),flags.cppm 的 is_clang 分支改由
+  数据驱动;`ProviderCapabilities.has_builtin_p1689_scan` 取代 ninja 后端的
+  is_gcc 门;`Toolchain::envOverrides`(EnvVar 表,注入 ninja 子进程环境,
+  为 MSVC 后端 INCLUDE/LIB/PATH 预留);gcc provider 增加与 clang 同形的
+  `std_module_build_commands`(命令序列);`resolve_link_model` 在 Windows
+  显式返回 PE 空模型。设计:`.agents/docs/2026-07-13-toolchain-backend-
+  abstraction-msvc-mingw-design.md` + 同日触点审计文档。
+
 ## [0.0.88] — 2026-07-13
 
 ### 新增

docs/03-toolchains.md

@@ -69,6 +69,30 @@ Available (run `mcpp toolchain install <compiler> <version>`):
 
 The entry marked with `*` is the current default toolchain. `@mcpp/...` is shorthand for `~/.mcpp/...`, used to keep the output narrower.
 
+## MinGW (Windows-native GCC, no Visual Studio required)
+
+On Windows, `mingw` installs a self-contained MinGW-w64 GCC (winlibs
+standalone build, UCRT runtime) into mcpp's sandbox — the same managed-xpkg
+model as `gcc`/`llvm`, no Visual Studio needed:
+
+```bash
+mcpp toolchain install mingw 16.1.0
+mcpp toolchain default mingw@16.1.0
+```
+
+It uses the regular GCC module pipeline (`gcm.cache`, `import std` via
+libstdc++'s `bits/std.cc`). Produced binaries statically link libstdc++ and
+libgcc by default, so they run standalone — no `libstdc++-6.dll` needs to
+travel next to your exe (opt out with `[build] static_stdlib = false`).
+`[build] linkage = "static"` upgrades that to a fully static link.
+
+In a manifest:
+
+```toml
+[toolchain]
+windows = "mingw@16.1.0"
+```
+
 ## MSVC (System Toolchain, Windows)
 
 MSVC is different from every other toolchain mcpp manages: it is a **system

mcpp.toml

@@ -1,6 +1,6 @@
 [package]
 name        = "mcpp"
-version     = "0.0.88"
+version     = "0.0.89"
 description = "Modern C++ build & package management tool"
 license     = "Apache-2.0"
 authors     = ["mcpp-community"]

src/build/flags.cppm

@@ -16,6 +16,7 @@ import mcpp.build.plan;
 import mcpp.platform;
 import mcpp.toolchain.clang;
 import mcpp.toolchain.detect;
+import mcpp.toolchain.dialect;
 import mcpp.toolchain.linkmodel;
 import mcpp.toolchain.provider;
 import mcpp.toolchain.registry;
@@ -122,10 +123,13 @@ std::string atomic_link_flag(const std::vector<std::filesystem::path>& linkDirs,
 CompileFlags compute_flags(const BuildPlan& plan) {
     CompileFlags f;
 
-    // ProviderCapabilities: centralised query point for per-toolchain decisions.
-    // Prefer caps.* checks over ad-hoc is_clang()/is_musl_target() calls for
-    // any new branching added to this function.
+    // Central query points for per-toolchain decisions — prefer these over
+    // ad-hoc is_clang()/is_gcc() calls:
+    //   caps   — what the toolchain can do (scan-deps, stdlib id, …)
+    //   d      — how a flag is SPELT (GNU "-I" vs MSVC "/I")
+    //   traits — BMI mechanics + module-flag spellings
     auto caps = mcpp::toolchain::capabilities_for(plan.toolchain);
+    const auto& d = mcpp::toolchain::dialect_for(plan.toolchain);
 
     // macOS minimum supported OS version for produced binaries.
     // Precedence: MACOSX_DEPLOYMENT_TARGET env (explicit per-invocation
@@ -152,7 +156,7 @@ CompileFlags compute_flags(const BuildPlan& plan) {
     std::string include_flags;
     for (auto& inc : plan.manifest.buildConfig.includeDirs) {
         auto abs = inc.is_absolute() ? inc : (plan.projectRoot / inc);
-        include_flags += " -I" + escape_path(abs);
+        include_flags += std::format(" {}{}", d.includePrefix, escape_path(abs));
     }
 
     // Sysroot / payload paths — resolved ONCE by the toolchain link model
@@ -208,11 +212,11 @@ CompileFlags compute_flags(const BuildPlan& plan) {
         f.sysroot = link_toolchain_flags;
     }
 
-    // Binutils -B flag
+    // Binutils -B flag — a GCC/libstdc++ payload concern (musl bundles its
+    // own as/ld; Clang and MSVC never take an external binutils).
     bool isMuslTc = mcpp::toolchain::is_musl_target(plan.toolchain);
-    bool isClang = mcpp::toolchain::is_clang(plan.toolchain);
     std::filesystem::path binutilsBin;
-    if (!isMuslTc && !isClang) {
+    if (!isMuslTc && caps.stdlib_id == "libstdc++") {
         auto ar = mcpp::toolchain::archive_tool(plan.toolchain);
         if (!ar.empty())
             binutilsBin = ar.parent_path();
@@ -231,8 +235,8 @@ CompileFlags compute_flags(const BuildPlan& plan) {
     // unless the profile pins -O0.
     auto& prof = plan.manifest.buildConfig;
     std::string opt_flag = isMuslTc && prof.optLevel != "0"
-        ? " -Og" : (" -O" + prof.optLevel);
-    if (prof.debug) opt_flag += " -g";
+        ? " -Og" : std::format(" {}{}", d.optPrefix, prof.optLevel);
+    if (prof.debug) opt_flag += std::format(" {}", d.debugFlags);
     if (prof.lto)   opt_flag += " -flto";
 
     // User link flags
@@ -247,20 +251,25 @@ CompileFlags compute_flags(const BuildPlan& plan) {
         plan.manifest.buildConfig.cStandard.empty() ? "c11" : plan.manifest.buildConfig.cStandard;
 
     // Assemble
-    // -fmodules is a GCC-only flag; Clang uses a different module ABI and does
-    // not need it.  caps.stdlib_id distinguishes GCC (libstdc++) from Clang
-    // (libc++ / msvc-stl) without an extra is_clang() call.
-    std::string module_flag = (caps.stdlib_id == "libstdc++") ? " -fmodules" : "";
+    // Module-flag spellings come from BmiTraits: GCC needs -fmodules on every
+    // TU (BMIs implicit); Clang/MSVC reference the staged std BMI and a BMI
+    // search dir explicitly (spelled -fmodule-file=/-fprebuilt-module-path vs
+    // /reference//ifcSearchDir).
+    auto traits = mcpp::toolchain::bmi_traits(plan.toolchain);
+    std::string module_flag{traits.compileModulesFlag};
     std::string std_module_flag;
-    if (isClang && !plan.stdBmiPath.empty()) {
-        std_module_flag = " -fmodule-file=std=" + escape_path(staged_std_bmi_path(plan));
+    if (!traits.stdBmiUsePrefix.empty() && !plan.stdBmiPath.empty()) {
+        std_module_flag = std::string(traits.stdBmiUsePrefix)
+                        + escape_path(staged_std_bmi_path(plan));
     }
     std::string std_compat_module_flag;
-    if (isClang && !plan.stdCompatBmiPath.empty()) {
+    if (!traits.stdCompatBmiUsePrefix.empty() && !plan.stdCompatBmiPath.empty()) {
+        // NOTE: staging path is Clang's today; registry-dispatch when the
+        // MSVC backend lands (std.compat.ixx staging).
         auto compatDst = mcpp::toolchain::clang::staged_std_compat_bmi_path(plan.outputDir);
-        std_compat_module_flag = " -fmodule-file=std.compat=" + escape_path(compatDst);
+        std_compat_module_flag = std::string(traits.stdCompatBmiUsePrefix)
+                               + escape_path(compatDst);
     }
-    auto traits = mcpp::toolchain::bmi_traits(plan.toolchain);
     std::string prebuilt_module_flag;
     if (traits.needsPrebuiltModulePath) {
         // Absolute path: a bare `pcm.cache` / `gcm.cache` works at ninja
@@ -272,22 +281,32 @@ CompileFlags compute_flags(const BuildPlan& plan) {
         // resolution fails with `module 'X' not found`. The other
         // `-fmodule-file=` flags in this block are already escape_path'd
         // (absolute) for the same reason — this one was a leftover.
-        prebuilt_module_flag = std::format(" -fprebuilt-module-path={}",
-            escape_path(plan.outputDir / traits.bmiDir));
+        prebuilt_module_flag = std::string(traits.bmiSearchPrefix)
+                             + escape_path(plan.outputDir / traits.bmiDir);
     }
     std::string cxx_std_flag =
-        plan.cppStandardFlag.empty() ? std::string("-std=c++23") : plan.cppStandardFlag;
+        plan.cppStandardFlag.empty()
+            ? std::format("{}c++23", d.stdPrefix) : plan.cppStandardFlag;
     f.cxx = std::format("{}{}{}{}{}{}{}{}{}{}", cxx_std_flag, module_flag, std_module_flag,
                         std_compat_module_flag, prebuilt_module_flag,
                         opt_flag, pic_flag, compile_toolchain_flags, b_flag, include_flags);
-    f.cc = std::format("-std={}{}{}{}{}{}", c_std, opt_flag, pic_flag, compile_toolchain_flags,
-                       b_flag, include_flags);
+    f.cc = std::format("{}{}{}{}{}{}{}", d.stdPrefix, c_std, opt_flag, pic_flag,
+                       compile_toolchain_flags, b_flag, include_flags);
 
     // Link flags
     f.staticStdlib = plan.manifest.buildConfig.staticStdlib;
     f.linkage = plan.manifest.buildConfig.linkage;
     std::string full_static = (mcpp::platform::supports_full_static && f.linkage == "static") ? " -static" : "";
-    std::string static_stdlib = (f.staticStdlib && !isClang && !mcpp::platform::is_windows) ? " -static-libstdc++" : "";
+    // Static C++ stdlib: a libstdc++ (GCC/MinGW) concern. On Windows a MinGW
+    // toolchain also statically links libgcc, so produced binaries don't
+    // depend on libstdc++-6.dll / libgcc_s DLLs from the toolchain dir
+    // (portable-by-default, same spirit as the macOS static-libc++ path).
+    std::string static_stdlib;
+    if (f.staticStdlib && caps.stdlib_id == "libstdc++") {
+        static_stdlib = " -static-libstdc++";
+        if constexpr (mcpp::platform::is_windows)
+            static_stdlib += " -static-libgcc";
+    }
     std::string runtime_dirs;
     if constexpr (mcpp::platform::supports_rpath) {
         // Toolchain runtime dirs (glibc/gcc) as before...
@@ -320,7 +339,30 @@ CompileFlags compute_flags(const BuildPlan& plan) {
     if (prof.strip) link_extra += " -s";
 
     if constexpr (mcpp::platform::is_windows) {
-        f.ld = user_ldflags + link_extra;
+        // PE link: no rpath/loader/payload model. MSVC-ABI Clang needs
+        // nothing extra (MSVC STL/SDK via the driver); MinGW adds the static
+        // libstdc++/libgcc pair (static_stdlib above) and -B so its own
+        // binutils resolve, plus `-static` for full static when requested
+        // (MinGW supports it, unlike MSVC-ABI links).
+        std::string mingw_static;
+        std::string mingw_stdexp;
+        if (caps.stdlib_id == "libstdc++") {
+            // `-static` for the whole link — winlibs' own recommendation for
+            // standalone exes. The piecemeal recipe (-static-libstdc++ +
+            // -Wl,-Bstatic -lwinpthread) verifiably loses to the driver's
+            // implicit closing libs: CI import tables still showed
+            // libwinpthread-1.dll. System DLLs (KERNEL32/UCRT) still resolve
+            // via their import libs. Tied to staticStdlib so
+            // [build] static_stdlib=false opts back into DLL-coupled links.
+            if (f.staticStdlib || f.linkage == "static")
+                mingw_static = " -static";
+            // std::print's terminal probe (__open_terminal /
+            // __write_to_terminal, bits/print.h) lives in libstdc++exp.a on
+            // Windows targets — plain -lstdc++ leaves them undefined.
+            mingw_stdexp = " -lstdc++exp";
+        }
+        f.ld = std::format("{}{}{}{}{}{}", mingw_static, static_stdlib, b_flag,
+                           user_ldflags, mingw_stdexp, link_extra);
     } else if constexpr (mcpp::platform::needs_explicit_libcxx) {
         // macOS. Two min-version concerns (see xlings
         // .agents/docs/2026-06-05-macos-min-version-support.md):

src/build/ninja_backend.cppm

@@ -25,6 +25,8 @@ import mcpp.build.hermetic;
 import mcpp.build.compile_commands;
 import mcpp.dyndep;
 import mcpp.toolchain.detect;
+import mcpp.toolchain.dialect;
+import mcpp.toolchain.provider;
 import mcpp.toolchain.registry;
 import mcpp.xlings;
 import mcpp.platform;
@@ -258,10 +260,12 @@ std::string emit_ninja_string(const BuildPlan& plan) {
     // dyndep requires P1689 scanning capability:
     //   GCC: built-in -fdeps-format=p1689r5
     //   Clang: external clang-scan-deps tool (same P1689 output format)
-    bool has_scanner = mcpp::toolchain::is_gcc(plan.toolchain)
-                    || !plan.scanDepsPath.empty();
+    //   (MSVC /scanDependencies is the future third driver — scanner design §3a)
+    auto caps = mcpp::toolchain::capabilities_for(plan.toolchain);
+    bool has_scanner = caps.has_builtin_p1689_scan || !plan.scanDepsPath.empty();
     bool dyndep = dyndep_mode_enabled() && has_scanner;
     auto traits = mcpp::toolchain::bmi_traits(plan.toolchain);
+    const auto& dial = mcpp::toolchain::dialect_for(plan.toolchain);
     std::string out;
     auto append = [&](std::string s) { out += std::move(s); };
 
@@ -331,53 +335,65 @@ std::string emit_ninja_string(const BuildPlan& plan) {
     // Runtime library paths for private toolchain executables are scoped onto
     // the ninja subprocess instead of being emitted into each visible rule.
 
+    // Command spellings come from the toolchain's CommandDialect (gnu vs
+    // msvc); the rule *structure* is shared across compilers.
     std::string module_output_flag = traits.needsExplicitModuleOutput
-        ? " -fmodule-output=$bmi_out" : "";
+        ? std::string(traits.moduleOutputPrefix) + "$bmi_out" : "";
+    const std::string compile_tail = std::format(
+        "{} $in {}$out", dial.compileOnly, dial.outputObjPrefix);
     append("rule cxx_module\n");
     if constexpr (mcpp::platform::is_windows) {
         // Windows: skip BMI restat optimization (requires POSIX shell).
         append(std::format("  command = "
-               "$cxx $local_includes $cxxflags $unit_cxxflags{} -c $in -o $out\n", module_output_flag));
+               "$cxx $local_includes $cxxflags $unit_cxxflags{} {}\n",
+               module_output_flag, compile_tail));
     } else {
         append(std::format("  command = "
                "if [ -n \"$bmi_out\" ] && [ -f \"$bmi_out\" ]; then "
                  "cp -p \"$bmi_out\" \"$bmi_out.bak\"; "
                "fi && "
-               "$cxx $local_includes $cxxflags $unit_cxxflags{} -c $in -o $out && "
+               "$cxx $local_includes $cxxflags $unit_cxxflags{} {} && "
                "if [ -n \"$bmi_out\" ] && [ -f \"$bmi_out.bak\" ] && "
                   "cmp -s \"$bmi_out\" \"$bmi_out.bak\"; then "
                  "mv \"$bmi_out.bak\" \"$bmi_out\"; "
                "else "
                  "rm -f \"$bmi_out.bak\"; "
-               "fi\n", module_output_flag));
+               "fi\n", module_output_flag, compile_tail));
     }
     append("  description = MOD $out\n");
     if (dyndep)
         append("  restat = 1\n");
     append("\n");
 
     append("rule cxx_object\n");
-    append("  command = $cxx $local_includes $cxxflags $unit_cxxflags -c $in -o $out\n");
+    append(std::format(
+        "  command = $cxx $local_includes $cxxflags $unit_cxxflags {}\n",
+        compile_tail));
     append("  description = OBJ $out\n");
     if (dyndep)
         append("  restat = 1\n");
     append("\n");
 
     if (need_c_rule) {
         append("rule c_object\n");
-        append("  command = $cc $local_includes $cflags $unit_cflags -c $in -o $out\n");
+        append(std::format(
+            "  command = $cc $local_includes $cflags $unit_cflags {}\n",
+            compile_tail));
         append("  description = CC $out\n");
         if (dyndep)
             append("  restat = 1\n");
         append("\n");
     }
 
+    // Link rule: driver-style today (g++/clang++ act as the linker). The
+    // dialect's LinkStyle::SeparateLinker (link.exe /OUT: + rspfile) is the
+    // MSVC backend's insertion point — unreachable until that lands.
     append("rule cxx_link\n");
     append("  command = $cxx $in -o $out $ldflags $unit_ldflags\n");
     append("  description = LINK $out\n\n");
 
     append("rule cxx_archive\n");
-    append("  command = $ar rcs $out $in\n");
+    append(std::format("  command = {}\n", dial.archiveCmd));
     append("  description = AR $out\n\n");
 
     append("rule cxx_shared\n");
@@ -811,6 +827,11 @@ std::expected<BuildResult, BuildError> NinjaBackend::build(const BuildPlan& plan
     std::vector<std::pair<std::string, std::string>> nenv;
     if (r.runtimeEnvKey != "-" && !r.runtimeEnvValue.empty())
         nenv.emplace_back(r.runtimeEnvKey, r.runtimeEnvValue);
+    // Toolchain-declared env (empty for GCC/Clang; MSVC's INCLUDE/LIB/PATH).
+    // NOTE: not persisted in the fast-path cache yet — revisit when the MSVC
+    // backend lands (its fast path must re-derive these from detection).
+    for (auto& ev : plan.toolchain.envOverrides)
+        nenv.emplace_back(ev.key, ev.value);
 
     auto cap = mcpp::platform::process::capture_exec(nargv, nenv);
     std::string out = cap.output;