fix(toolchain): clang cfg gains the C-header axis (v0.0.84)

fixup_clang_cfg's regenerated cfg covered the link axis (-B/-L/loader/
rpath) but omitted the C library and kernel headers — a direct
`clang hello.c` only worked when the HOST happened to ship /usr/include
(silently non-hermetic; hard failure on header-less machines). The cfg
now carries -isystem for the glibc payload headers and the linux-headers
payload, ordered AFTER the libc++ block (its C-header wrappers reach libc
via #include_next) — byte-consistent with what xim-pkgindex's llvm.lua
install hook generates, so the two cfg writers can no longer diverge.

The C driver cfg (clang.cfg) gets the headers directly; the C++ cfg gets
them after the libc++ includes. Fixup rev bumped to hermetic-3 so existing
payloads re-converge on their next build. Verified with host headers
masked (--sysroot=<empty dir>): cfg-driven bare clang and clang++ both
compile and run; negative control without the payload headers fails as
expected. mcpp's own builds are unaffected (the link model has always
supplied its own header flags).

Author: Sunrisepeak

CHANGELOG.md

@@ -3,7 +3,22 @@
 > 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/)。
 
-## [0.0.83] — 2026-07-07
+## [0.0.84] — 2026-07-08
+
+### 修复 / 完善
+
+- **clang cfg 头文件轴补齐(供人类直接使用的完备性)**:`fixup_clang_cfg` 再生的
+  cfg 此前只覆盖链接轴(`-B`/`-L`/loader/rpath),缺 C 库与内核头——裸
+  `clang hello.c` 只有在宿主恰好装有 `/usr/include` 时才能编译(静默不 hermetic,
+  无宿主头的机器直接失败)。现补上 `-isystem <glibc payload>/include` 与
+  `-isystem <linux-headers payload>/include`,置于 libc++ 头块**之后**
+  (保持 `#include_next` 链),与 xim-pkgindex 侧 `llvm.lua` 装机生成的 cfg
+  内容一致——两个写手不再漂移。fixup rev 升至 `hermetic-3`,存量 payload 在
+  下次构建时自动再收敛。已实测:宿主头被屏蔽(`--sysroot=<空目录>`)下,
+  cfg 驱动的裸 `clang`/`clang++` 编译运行均成功。mcpp 自身构建不受影响
+  (linkmodel 一直自带头轴)。
+
+
 
 ### 修复
 

mcpp.toml

@@ -1,6 +1,6 @@
 [package]
 name        = "mcpp"
-version     = "0.0.83"
+version     = "0.0.84"
 description = "Modern C++ build & package management tool"
 license     = "Apache-2.0"
 authors     = ["mcpp-community"]

src/toolchain/fingerprint.cppm

@@ -18,7 +18,7 @@ import mcpp.toolchain.detect;
 
 export namespace mcpp::toolchain {
 
-inline constexpr std::string_view MCPP_VERSION = "0.0.83";
+inline constexpr std::string_view MCPP_VERSION = "0.0.84";
 
 struct FingerprintInputs {
     Toolchain                       toolchain;

src/toolchain/post_install.cppm

@@ -232,7 +232,7 @@ export void fixup_clang_cfg(const std::filesystem::path& payloadRoot,
         }
     }
 
-    std::string common, cxxOnly;
+    std::string common, cxxOnly, cHdr;
     auto cxxInclude = payloadRoot / "include" / "c++" / "v1";
     if constexpr (mcpp::platform::is_macos) {
         // macOS keeps its historical cfg semantics: the C library and the
@@ -256,6 +256,28 @@ export void fixup_clang_cfg(const std::filesystem::path& payloadRoot,
         }
         common += "-fuse-ld=lld\n--rtlib=compiler-rt\n--unwindlib=libunwind\n";
 
+        // HEADER axis (C and C++ drivers alike): the C library and kernel
+        // headers come from the same payloads the link axis uses. Without
+        // these, a direct `clang hello.c` only works when the HOST happens
+        // to ship /usr/include — silently non-hermetic, broken on
+        // header-less machines. For C++ they must come AFTER the libc++
+        // block (its C-header wrappers reach libc via #include_next), so
+        // they are collected separately and appended in order below —
+        // byte-consistent with what llvm.lua's install hook generates.
+        if (!glibcLibDir.empty()) {
+            auto glibcInclude = glibcLibDir.parent_path() / "include";
+            if (std::filesystem::exists(glibcInclude / "features.h"))
+                cHdr += "-isystem " + glibcInclude.string() + "\n";
+            constexpr std::string_view kLinuxLimits = "include/linux/limits.h";
+            auto linuxHeaders = mcpp::xlings::paths::find_sibling_package(
+                payloadRoot / "bin" / "clang++", "linux-headers", kLinuxLimits);
+            if (!linuxHeaders)
+                linuxHeaders = mcpp::xlings::paths::find_home_tool(
+                    "linux-headers", kLinuxLimits);
+            if (linuxHeaders)
+                cHdr += "-isystem " + (*linuxHeaders / "include").string() + "\n";
+        }
+
         if (std::filesystem::exists(cxxInclude)) {
             cxxOnly += "-nostdinc++\n-stdlib=libc++\n";
             cxxOnly += "-isystem " + cxxInclude.string() + "\n";
@@ -264,6 +286,9 @@ export void fixup_clang_cfg(const std::filesystem::path& payloadRoot,
             auto tripleInclude = payloadRoot / "include" / triple / "c++" / "v1";
             if (std::filesystem::exists(tripleInclude))
                 cxxOnly += "-isystem " + tripleInclude.string() + "\n";
+        }
+        cxxOnly += cHdr;
+        if (!triple.empty()) {
             auto tripleLib = payloadRoot / "lib" / triple;
             if (std::filesystem::exists(tripleLib)) {
                 cxxOnly += "-L" + tripleLib.string() + "\n";
@@ -281,7 +306,7 @@ export void fixup_clang_cfg(const std::filesystem::path& payloadRoot,
         if (!name.ends_with(".cfg")) continue;
         const bool isCxx = name.find("++") != std::string::npos;
         std::ofstream os(it->path());
-        os << common << (isCxx ? cxxOnly : std::string{});
+        os << common << (isCxx ? cxxOnly : cHdr);
     }
 }
 
@@ -376,7 +401,7 @@ void llvm_post_install_fixup(const mcpp::config::GlobalConfig& cfg,
 // runtime libs. Idempotent via a content-fingerprinted marker.
 //
 // Bump when the fixup logic changes so existing installs re-run it.
-constexpr std::string_view kFixupRev = "hermetic-2";
+constexpr std::string_view kFixupRev = "hermetic-3";
 
 export void ensure_post_install_fixup(const mcpp::config::GlobalConfig& cfg,
                                       const std::filesystem::path& payloadRoot,