The package std module takes the prebuilt C library's tokens, and an unset iOS floor is the located SDK's version (2026.9.14.1)

.github/workflows/ci-macos-ios.yml

@@ -327,12 +327,12 @@ jobs:
         run: |
           set -euo pipefail
           rm -rf /tmp/iosplain && mkdir -p /tmp/iosplain/src && cd /tmp/iosplain
+          # NO FLOOR STATED: the row takes the located SDK's version, read
+          # through xcrun, and the artefact's LC_BUILD_VERSION minos says so.
           cat > mcpp.toml << 'TOML'
           [package]
           name = "iosplain"
           version = "0.1.0"
-          [build]
-          ios_deployment_target = "18.0"
           TOML
           printf 'import std;\nint main() { std::print("x\\n"); }\n' > src/main.cpp
           "$MCPP_DEV" build --target aarch64-ios-sim > mixed.log 2>&1 || { echo "FAIL: import std without llvm.libcxx no longer builds"; cat mixed.log; exit 1; }
@@ -350,6 +350,10 @@ jobs:
           grep -q -- '-isystem[^ ]*xim-x-llvm[^ ]*/c++/v1' "$ninja" && { echo "FAIL: the plain program still takes the payload's C++ headers"; exit 1; }
           art=$(ls target/aarch64-ios-sim/*/bin/iosplain | head -1)
           otool -L "$art" | grep -q '/usr/lib/libc++.1.dylib' || { echo "FAIL: the plain program does not link the SDK's libc++"; otool -L "$art"; exit 1; }
+          sdkver=$(xcrun --sdk iphonesimulator --show-sdk-version)
+          minos=$(otool -l "$art" | awk '/cmd LC_BUILD_VERSION/{f=1} f && $1=="minos"{print $2; exit}')
+          [ "$minos" = "$sdkver" ] || { echo "FAIL: with no floor stated, minos is '$minos' and the located SDK is $sdkver"; exit 1; }
+          echo "ok: an unset floor is the located SDK's version ($sdkver)"
           echo "ok: import std builds with the hazard named; plain C++ takes the SDK's headers and libc++; the builtins degradation is printed"
 
       # THE SUPPORTED PATH, which is what the `verified` tier claims: a runner

CHANGELOG.md

@@ -5,6 +5,22 @@
 
 ## [Unreleased]
 
+### 图里的 libc++ 之下,预编译 C 库的头文件也要进 std 模块的命令;iOS 行未写的部署下限取 SDK 的版本
+
+`llvm.libcxx` 的 CI 扩到它声明的每一行后量到两处引擎缺口。包提供的 std 模块在
+预编译时只拿到包自己的 `std-module-flags` 与图里各层的头文件目录,预编译 C 库
+(glibc、Apple SDK)的目录一个都没有:Linux 上它读的是 runner 的 `/usr/include`
+而不是载荷的 glibc(没有任何报告显示这一点),macOS 原生行停在 `mbstate_t`。现在
+这条命令从每个翻译单元用的同一个生产者(`host_compile_tokens`,C++ 层记为图里的)
+取 cfg 旁路、C 库目录、SDK 与部署下限。`docs/20` 曾承诺 iOS 行不写
+`ios_deployment_target` 时取 SDK 的默认;实测 clang 对无版本的 `arm64-apple-ios`
+拒绝线程局部存储(libc++abi 用到它),所以那个默认比机器上任何 SDK 都旧。现在
+定位 SDK 时同时读 `xcrun --sdk <name> --show-sdk-version`,写进同一个槽。
+
+- 判据:`tests/e2e/663` 断言包 std 模块记录的命令点名载荷的 glibc;`ci-macos-ios`
+  的纯 C++ 夹具不写下限,断言产物 `LC_BUILD_VERSION minos` 等于定位到的 SDK 版本;
+  `mcpplibs/libcxx` 的 CI 在 linux、aarch64-macos、aarch64-ios、两个模拟器行上各量一次。
+
 ### 一个框架与它的生态库仍会撞到的引擎缺口:#630 的十项
 
 #630 汇总了 HuxerUI 在六个平台上落地后引擎仍欠的十项。每一项都先在

docs/20-toolchains.md

@@ -723,9 +723,12 @@ Target aarch64-ios-sim → arm64-apple-ios18.0-simulator
 which are Apple's own spellings. No `-miphoneos-version-min` flag is emitted:
 the triple fully determines the platform and the minimum, and a flag would be a
 second place answering a question the triple already answers. Leaving the key
-unset is legal and means the SDK's own default, which clang supplies for an
-Apple target -- unlike Android, where bionic refuses an unversioned triple
-outright.
+unset is legal and means the located SDK's own version, which mcpp reads from
+`xcrun --sdk <name> --show-sdk-version` and writes into the same slot: clang's
+own default for an unversioned iOS triple is older than any SDK on the machine
+(it refused thread-local storage, which libc++abi uses; measured on Xcode
+16.4), so the triple is versioned before the driver sees it. Android differs
+in the other direction: bionic refuses an unversioned triple outright.
 
 ### The simulator's shape, and its boundary
 

docs/zh/20-toolchains.md

@@ -649,8 +649,10 @@ Target aarch64-ios-sim → arm64-apple-ios18.0-simulator
 
 这是 Apple 自己的拼法。不发 `-miphoneos-version-min` 标志:三元组已经完全决定了
 平台与最低版本,而一个标志会成为第二个回答三元组已经回答过的问题的地方。不写这个键
-是合法的,含义是 SDK 自己的默认值 —— 对一个 Apple 目标,clang 会供给它 ——
-这与 Android 不同,那里 bionic 会直接拒绝一个不带版本的三元组。
+是合法的,含义是定位到的 SDK 自己的版本:mcpp 用 `xcrun --sdk <name> --show-sdk-version`
+读出它并写进同一个槽。clang 对不带版本的 iOS 三元组给的默认比机器上任何 SDK 都旧
+(它拒绝了 libc++abi 用到的线程局部存储;在 Xcode 16.4 上实测),所以三元组在驱动看到
+之前就带上了版本。Android 的差别在另一个方向:bionic 会直接拒绝一个不带版本的三元组。
 
 ### 模拟器的形状与它的边界
 

mcpp.toml

@@ -1,6 +1,6 @@
 [package]
 name        = "mcpp"
-version = "2026.9.13.2"
+version = "2026.9.14.1"
 description = "Modern C++ build & package management tool"
 license     = "Apache-2.0"
 authors     = ["mcpp-community"]

modules/platform/src/macos/macos.cppm

@@ -74,6 +74,13 @@ bool sdkroot_answers(const std::filesystem::path& candidate,
 // today's behaviour for today's callers.
 std::optional<std::filesystem::path> sdk_path(std::string_view sdk = sdk_macos);
 
+// The version the located SDK was made for, as `xcrun --sdk <name>
+// --show-sdk-version` reports it ("18.5"). Empty off macOS and when xcrun
+// cannot answer. Read for an iOS row whose manifest states no deployment
+// floor, since clang's own default for an unversioned iOS triple is older
+// than any SDK on the machine (it refused thread-local storage; measured).
+std::optional<std::string> sdk_version(std::string_view sdk);
+
 // Built-in default deployment floor (rustc-style: every target has a
 // baseline). 14.0 = the floor of the official LLVM static libc++
 // archives; with the default-static stdlib this makes `mcpp run`
@@ -194,6 +201,17 @@ bool sdkroot_answers(const std::filesystem::path& candidate,
     return sdk == sdk_macos;
 }
 
+std::optional<std::string> sdk_version(std::string_view sdk) {
+#if defined(__APPLE__)
+    auto v = run_capture_trimmed(std::format("xcrun --sdk {} --show-sdk-version 2>/dev/null", sdk));
+    if (v.empty()) return std::nullopt;
+    return v;
+#else
+    (void)sdk;
+    return std::nullopt;
+#endif
+}
+
 std::optional<std::filesystem::path> sdk_path(std::string_view sdk) {
     auto layout = sdk_layout(sdk);
     if (!layout) return std::nullopt;

modules/versioning/src/version.cppm

@@ -31,6 +31,6 @@ import std;
 
 export namespace mcpp {
 
-inline constexpr std::string_view MCPP_VERSION = "2026.9.13.2";
+inline constexpr std::string_view MCPP_VERSION = "2026.9.14.1";
 
 } // namespace mcpp

src/build/prepare.cppm

@@ -32,6 +32,7 @@ import mcpp.modgraph.graph;
 import mcpp.modgraph.scanner;
 import mcpp.modgraph.validate;
 import mcpp.toolchain.clang;
+import mcpp.toolchain.hostflags;   // the compile-token producer the package std module reuses
 import mcpp.toolchain.cppfly;
 import mcpp.toolchain.detect;
 import mcpp.toolchain.dialect;
@@ -1664,10 +1665,12 @@ std::string min_platform_version(const mcpp::manifest::Manifest& m,
     // one target, which is why they still share this function's single return
     // and the single fingerprint slot behind it.
     //
-    // Empty is a legal answer here and not a refusal, unlike Android's. The
-    // asymmetry is a measured property of the platforms rather than a policy:
-    // Darwin's driver supplies the SDK's own deployment target when the
-    // triple carries none, and bionic rejects the unversioned triple outright.
+    // Empty is a legal answer here and not a refusal, unlike Android's, and
+    // for the iOS rows prepare fills it with the located SDK's version before
+    // this is read: an unversioned `arm64-apple-ios` made clang refuse
+    // thread-local storage (measured, Xcode 16.4), so the driver's own
+    // default is not the SDK's. Bionic rejects the unversioned triple
+    // outright, which is the other half of the asymmetry.
     if (t.is_ios()) return m.buildConfig.iosDeploymentTarget;
     return mcpp::platform::macos::deployment_target(
         m.buildConfig.macosDeploymentTarget);
@@ -2591,6 +2594,20 @@ prepare_build(bool print_fingerprint,
                 ? mcpp::platform::macos::sdk_iphonesim
                 : mcpp::platform::macos::sdk_iphoneos;
             appleSdkLocated = mcpp::platform::macos::sdk_path(which);
+            // AN UNSET FLOOR IS THE LOCATED SDK'S VERSION, READ RATHER THAN
+            // LEFT TO THE DRIVER. `docs/20` promised that an unversioned
+            // triple meant the SDK's own default; measured on macos-15 with
+            // Xcode 16.4, clang given `arm64-apple-ios` with no version
+            // refused thread-local storage for the target, which libc++abi
+            // uses, so the default it chose was older than any SDK on the
+            // machine. The version `xcrun` reports for the located SDK is the
+            // one the SDK was made for, and it enters the manifest here so
+            // that the fingerprint slot, the effective triple and every
+            // report read one value.
+            if (appleSdkLocated && m->buildConfig.iosDeploymentTarget.empty()) {
+                if (auto v = mcpp::platform::macos::sdk_version(which))
+                    m->buildConfig.iosDeploymentTarget = *v;
+            }
             if (!appleSdkLocated) {
                 // A CODE, BECAUSE THE MATRIX COMPARES REASONS AND NOT ONLY
                 // OUTCOMES. A refusal with no code is recorded as `other`,
@@ -10714,16 +10731,6 @@ prepare_build(bool print_fingerprint,
             // DWARF. Same function, not a second copy of the decision.
             for (auto& f : mcpp::toolchain::graph_runtime_compile_flags(*tc))
                 flags += " " + f;
-            // AND THE APPLE CROSS TARGET'S SDK, WHICH THE TOOLCHAIN RESOLUTION
-            // HAD ALREADY PUT ON THIS CHANNEL AND THIS ASSIGNMENT REPLACES.
-            // The module's C library is the SDK's on the iOS rows (the
-            // package supplies the C++ layer alone), and without the sysroot
-            // the precompile stops on `mbstate_t` inside libc++'s own
-            // headers. Measured on macos-15 with `llvm.libcxx` over
-            // `arm64-apple-ios18.0`: twenty "reference to unresolved using
-            // declaration" errors, every one a C library type.
-            if (!tc->appleSdkRoot.empty())
-                flags += " -isysroot " + mcpp::xlings::shq(tc->appleSdkRoot.string());
         }
         // Everything up to here says which machine the module is for; what
         // follows says where its headers are. The codegen step needs only the
@@ -10779,6 +10786,42 @@ prepare_build(bool print_fingerprint,
         // its own translation units see. Measured: without them the module
         // reaches musl's <time.h> and stops on `clockid_t', a name that header
         // declares only under the macro the package carries.
+        // THE PREBUILT C LIBRARY'S OWN TOKENS, FROM THE PRODUCER EVERY UNIT
+        // USES. A package that supplies the C++ layer over a prebuilt C
+        // library (`llvm.libcxx` over glibc, or over an Apple SDK) has no
+        // way to name that library's headers in its manifest, and the
+        // target-side broadcast below carries only graph layers. Without
+        // these the precompile reads whatever the driver finds on its own:
+        // on Linux the runner's `/usr/include` rather than the payload's
+        // glibc, a host dependency no report showed; on macOS nothing, and
+        // the precompile stops on `mbstate_t`; on the iOS rows nothing, and
+        // it stopped on the same name. Measured on 2026-09-14 across the
+        // three. `host_compile_tokens` is what every translation unit of the
+        // build gets, asked with the C++ layer marked as the graph's so that
+        // it withholds the payload's libc++ and emits the rest: the cfg
+        // bypass, the C library's directories, the SDK and the deployment
+        // floor. Same function, not a second copy.
+        //
+        // AND LAST ON THE COMMAND, after the package's own directories:
+        // `-isystem` order is search order, and libc++'s headers must precede
+        // the C library's, which libc++ states in as many words (`<cctype>`
+        // stops the build if it reaches a `<ctype.h>` that is not its own).
+        // Emitted ahead of them, glibc's `<math.h>` shadowed libc++'s wrapper
+        // and `<complex>` failed on `std::__builtin_isnan` (measured).
+        if (tc->cAbiPrebuilt) {
+            mcpp::toolchain::HostFlagOptions hopt;
+            hopt.cfgBypass             = mcpp::toolchain::HostFlagOptions::CfgBypass::Always;
+            hopt.cAbiPrebuilt          = true;
+            hopt.cxxFromGraph          = true;
+            hopt.appleSdkRoot          = tc->appleSdkRoot;
+            hopt.macosDeploymentTarget = mcpp::platform::macos::deployment_target(
+                m->buildConfig.macosDeploymentTarget);
+            for (auto& t : mcpp::toolchain::host_compile_tokens(
+                     *tc, hopt, mcpp::toolchain::no_escape)) {
+                const auto q = " " + mcpp::xlings::shq(t);
+                if (flags.find(q) == std::string::npos) flags += q;
+            }
+        }
         for (auto& f : targetSideUsage.cxxflags)
             flags += " " + mcpp::xlings::shq(f);
         tc->stdModuleFlags = flags;

tests/e2e/663_a_graph_libcxx_over_the_payloads_c_library.sh

@@ -68,6 +68,15 @@ grep -q -- '-nostdinc++' "$ninja" || fail "the compile lines carry no -nostdinc+
 grep -q -- '-nostdlib++' "$ninja" || fail "the link line carries no -nostdlib++" "$ninja"
 grep -q -- 'xim-x-llvm[^ ]*libc++\(abi\)\?\.a' "$ninja" \
     && fail "the link line still names the payload's libc++ archives" "$ninja"
+# The package's std module was precompiled against the payload's C library,
+# not against whatever the driver found on the machine: the recorded command
+# names the glibc payload. Before this assertion the command carried only
+# `--no-default-config -nostdinc++` and the runner's /usr/include stood in,
+# a host dependency no report showed.
+stdjson=$(grep -l 'llvm.libcxx\|libcxx' "$MCPP_HOME"/build-cache/v1/std/*/std-module.json 2>/dev/null | xargs -r ls -t | head -1)
+[ -n "$stdjson" ] || fail "no std-module.json records the package's module under $MCPP_HOME/build-cache/v1/std"
+grep -q 'xim-x-glibc' "$stdjson" \
+    || fail "the package std module's command does not name the payload's glibc" "$stdjson"
 bin=$(ls target/*/*/bin/app | head -1)
 ldd "$bin" | grep -q 'libc++' && fail "the artefact still links a libc++ shared object" <(ldd "$bin")
 out=$("$bin") || fail "the program exited non-zero"