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fix(mingw): view only a prefix that holds a Linux system

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The first fix showed clang every mingw prefix through a view of its
mingw-w64 parts. That broke a prefix that holds mingw-w64 alone, where
Windows libraries installed with --prefix land in include/ and lib/:
with CRAFTER_MINGW_DIR=/opt/mingw, <SDL2/SDL.h> and -lSDL2 were no
longer found. Such a prefix is clang's sysroot whole again. Only a
prefix that also holds a Linux system gets the view
(Toolchain::mingwPrefixIsSystem): the host's /usr inside the Flatpak,
whatever its include/ holds, and a prefix whose include/ has a C
library's features.h, which every glibc and musl header includes and
mingw-w64 has no use for, as CRAFTER_MINGW_DIR=/usr has.

MakeMingwSysroot makes the view in the cache, or in
$XDG_RUNTIME_DIR/crafter.build when the cache's filesystem takes no
symbolic links (vfat, exFAT, CIFS without unix extensions): the XDG
spec promises them there, and nothing else in the cache needs them.
Its path is absolute, because CMake runs the compiler from directories
of its own and a relative cache did not resolve from there. The prefix
is resolved once, absolute and lexically normal, so /opt/mingw/ and
/opt/mingw are one prefix and not two builds.

clang names a header by the path it found it at, so every diagnostic
from a viewed mingw-w64 header named a hashed cache directory.
RunBuildCommand now writes paths into the view as paths into the
prefix, as BuildStdPcm did for its manifest messages already.

Also from the review of PR #44: SysrootCompileFlags builds a mingw
command, which can make a view, so it redirects the cache like the
other tests; the manifest filter's comment names what it still keeps
out; the C path asks MingwSysroot() once.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Jorijn van der Graaf 2026-10-31 22:58:30 +01:00
commit 06b61e84f9
Signed by: jorijnvdgraaf
GPG key ID: 2937E59CDCC1BCFB
8 changed files with 262 additions and 78 deletions
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114
implementations/Crafter.Build-Toolchain.cpp
View file

@ -54,9 +54,26 @@ namespace {
fs::create_directory_symlink(target, link, ec);
std::error_code ignored;
if (ec && fs::read_symlink(link, ignored) != target) {
throw fs::filesystem_error("cannot make the mingw-w64 sysroot view", target, link, ec);
throw fs::filesystem_error("cannot make a link", target, link, ec);
}
}
// `dir` made absolute and spelled one way, once, when the toolchain is
// resolved. The mingw prefix ends up as the target of links and in the
// names of build and cache directories: a relative path read later from
// another working directory would name something else, and /opt/mingw/
// next to /opt/mingw would rebuild everything for the same directory.
fs::path PrefixPath(const fs::path& dir) {
fs::path normal = fs::absolute(dir).lexically_normal();
if (!normal.has_filename() && normal.has_relative_path()) normal = normal.parent_path();
return normal;
}
// The view MingwSysroot() made and the prefix it shows, for
// MingwViewToPrefix. Written once, before ViewMade is set.
fs::path MadeView;
fs::path ViewedPrefix;
std::atomic<bool> ViewMade = false;
}
std::string Toolchain::LibcxxCompileFlags() const {
@ -150,14 +167,19 @@ Toolchain Crafter::ResolveToolchain(const ToolchainInputs& in) {
tc.wasiSysroot = "/usr/share/wasi-sysroot";
}
if (std::string_view dir = Env(in, "CRAFTER_MINGW_DIR"); !dir.empty()) {
// Made absolute here, once: the prefix becomes the target of links
// in the cache and part of directory names, and a relative path read
// later from another working directory would name something else.
tc.mingwPrefix = fs::absolute(fs::path(dir));
tc.mingwPrefix = PrefixPath(fs::path(dir));
// A prefix that holds a Linux system as well as mingw-w64, /usr
// itself, has that system's C library in include/: features.h, which
// every glibc and musl header includes and mingw-w64 has no use for.
// One that holds mingw-w64 alone stays the sysroot, so Windows
// libraries installed into its include/ and lib/ stay visible.
tc.mingwPrefixIsSystem = fs::exists(tc.mingwPrefix / "include" / "features.h");
} else if (!in.hostRoot.empty() && fs::exists(in.hostRoot / "usr" / "x86_64-w64-mingw32")) {
// The sandbox has no mingw-w64 of its own, and no mingw gcc on PATH
// for clang to find one by.
tc.mingwPrefix = in.hostRoot / "usr";
// for clang to find one by. The host's /usr is the host's system,
// whether or not its C library's headers are installed.
tc.mingwPrefix = PrefixPath(in.hostRoot / "usr");
tc.mingwPrefixIsSystem = true;
}
return tc;
}
@ -203,31 +225,69 @@ const Toolchain& Crafter::RequireToolchain() {
return tc;
}
const fs::path& Crafter::MingwSysroot() {
// Made on first use rather than by GetToolchain(), so only a mingw build
// writes to the cache for it, and a failure surfaces as that build's
// error instead of on every command.
static const fs::path Sysroot = []() -> fs::path {
const fs::path& prefix = GetToolchain().mingwPrefix;
if (prefix.empty()) return {};
// A view per prefix keeps two shells with different
// CRAFTER_MINGW_DIRs, which share one cache, from rewriting each
// other's.
const fs::path sysroot = GetCacheDir() / "mingw-sysroot" / std::format("{:016x}", std::hash<std::string>{}(prefix.string()));
// All clang's mingw driver takes from a sysroot other than its
// include/ and the rest of its lib/: the mingw-w64 tree (headers,
// libraries, and libstdc++ where a distro's cross gcc installs it)
// and gcc's per-target directory (crtbegin.o, libgcc, and the version
// that names libstdc++'s header directory), which openSUSE keeps
// under lib64. A link to nothing is skipped like a missing directory.
for (std::string_view entry : {"x86_64-w64-mingw32", "lib/gcc", "lib64/gcc"}) {
EnsureSymlink(prefix / entry, sysroot / entry);
fs::path Crafter::MakeMingwSysroot(const fs::path& prefix, std::span<const fs::path> parents) {
std::string reasons;
for (const fs::path& parent : parents) {
// One view per prefix: two shells with different CRAFTER_MINGW_DIRs
// share one cache and would otherwise rewrite each other's.
const fs::path sysroot = parent / "mingw-sysroot" / std::format("{:016x}", std::hash<std::string>{}(prefix.string()));
try {
// All clang's mingw driver takes from a sysroot other than its
// include/ and the rest of its lib/: the mingw-w64 tree (headers,
// libraries, and libstdc++ where a distro's cross gcc installs
// it) and gcc's per-target directory (crtbegin.o, libgcc, and the
// version that names libstdc++'s header directory), which
// openSUSE keeps under lib64. A link to nothing is skipped like a
// missing directory.
for (std::string_view entry : {"x86_64-w64-mingw32", "lib/gcc", "lib64/gcc"}) {
EnsureSymlink(prefix / entry, sysroot / entry);
}
return sysroot;
} catch (const std::exception& e) {
reasons += std::format("; {}", e.what());
}
return sysroot;
}
throw std::runtime_error(std::format("cannot make a sysroot that shows clang only the mingw-w64 parts of {}{}", prefix.string(), reasons));
}
const fs::path& Crafter::MingwSysroot() {
// Made on first use rather than by GetToolchain(), so that only what
// compiles for the mingw target, a build or an AST lint of one, writes
// anything for it, and a failure surfaces as that command's error
// instead of on every command.
static const fs::path Sysroot = []() -> fs::path {
const Toolchain& tc = GetToolchain();
if (!tc.mingwPrefixIsSystem) return tc.mingwPrefix;
// In the cache, or where the XDG spec promises symbolic links when
// the cache's filesystem takes none (vfat, exFAT, CIFS without unix
// extensions), which costs nothing else crafter-build caches.
// Absolute, because CMake runs the compiler from directories of its
// own.
std::vector<fs::path> parents = { fs::absolute(GetCacheDir()) };
if (const char* runtime = std::getenv("XDG_RUNTIME_DIR"); runtime && *runtime) {
parents.push_back(fs::absolute(fs::path(runtime) / "crafter.build"));
}
fs::path view = MakeMingwSysroot(tc.mingwPrefix, parents);
MadeView = view;
ViewedPrefix = tc.mingwPrefix;
ViewMade.store(true, std::memory_order_release);
return view;
}();
return Sysroot;
}
std::string Crafter::MingwViewToPrefix(std::string text) {
if (!ViewMade.load(std::memory_order_acquire)) return text;
// With the separator, so a --sysroot= naming the view itself, in a
// command line the output quotes, stays what was run.
const std::string view = (MadeView / "").string();
const std::string prefix = (ViewedPrefix / "").string();
for (std::size_t at = text.find(view); at != std::string::npos; at = text.find(view, at + prefix.size())) {
text.replace(at, view.size(), prefix);
}
return text;
}
std::int32_t Crafter::LibcxxVersion(const fs::path& includeDir) {
// "# define _LIBCPP_VERSION 230102", the one place libc++ states its
// release in a form the preprocessor does not have to be run for.