fix: give the mingw target a sysroot that holds mingw-w64 alone

Inside the Flatpak the mingw-w64 prefix is the host's /usr, and it was
clang's --sysroot as is. clang's mingw driver takes a sysroot for a tree
that holds mingw-w64 alone, and adds its include/ to the include path
and its lib/ to the library path. For /usr those are the Linux system's
own: every header mingw-w64 lacks came from glibc, and libstdc++'s
<ext/atomicity.h>, finding <sys/single_threaded.h>, had shared_ptr read
__libc_single_threaded, which nothing on Windows defines. Every program
that used one failed to link, among them every Crafter.Graphics Win32
executable, through Crafter.Asset's GLB loader. CRAFTER_MINGW_DIR=/usr
did the same outside the Flatpak (#43).

The sysroot is now MingwSysroot(): a directory in the cache, one per
prefix, holding only links to the prefix's x86_64-w64-mingw32/, lib/gcc/
and lib64/gcc/ (where openSUSE keeps gcc). Through it clang finds
mingw-w64, gcc's version and libstdc++ exactly as it does through the
mingw gcc on PATH, and nothing else. It is made by the first mingw
compile, link or CMake configure of a process, so no other command
writes to the cache for it and a failure to make it is that build's
error. The Toolchain field is now mingwPrefix, since clang never gets
the prefix itself, and it is made absolute when the toolchain is
resolved, as it ends up in link targets and directory names. Messages
keep naming paths under the prefix rather than under the view.

The prefix is also part of the mingw target's VariantId and of its std
PCM directory. Units do not track the std PCM they import: when the
fixed release built in a directory a broken build had left, the std
module was rebuilt and the objects compiled against glibc's headers
were only relinked, failing as before. As with a compiler update, a new
directory is what gets them rebuilt. It also keeps two releases that
share a cache, as the Flatpak's branches do, from rebuilding one std PCM
under each other's PCMs, and two prefixes apart. Without a prefix both
stay as they were: clang's own discovery has not changed.

Two shorter ways do not work: --sysroot=<prefix>/x86_64-w64-mingw32
loses the directory gcc's version names, so <string> is not found, and
clang ignores --gcc-toolchain and --gcc-install-dir for this target.

Fixes #43

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Jorijn van der Graaf 2026-10-31 20:48:06 +01:00
commit ab998081e1
Signed by: jorijnvdgraaf
GPG key ID: 2937E59CDCC1BCFB
7 changed files with 106 additions and 22 deletions

View file

@ -61,7 +61,7 @@ int main() {
Check(tc.libcxxVersion == LibcxxVersion("/usr/include/c++/v1"), "the system libc++ headers state the release of the system module source");
Check(tc.stdModulesDir.empty(), "no crafter-build prefix, no shipped module sources");
Check(tc.wasiSysroot == "/usr/share/wasi-sysroot", "the system wasi sysroot is the default");
Check(tc.mingwSysroot.empty(), "outside a sandbox, clang finds mingw-w64 itself: no --sysroot");
Check(tc.mingwPrefix.empty(), "outside a sandbox, clang finds mingw-w64 itself: no prefix");
Check(tc.LibcxxCompileFlags().empty() && tc.LibcxxLinkFlags().empty(), "the PATH fallback adds no libc++ flags");
}
{
@ -144,7 +144,9 @@ int main() {
in.env["CRAFTER_MINGW_DIR"] = "/opt/mingw";
Toolchain tc = ResolveToolchain(in);
Check(tc.wasiSysroot == "/opt/wasi", "CRAFTER_BUILD_WASI_SYSROOT overrides the wasi sysroot");
Check(tc.mingwSysroot == "/opt/mingw", "CRAFTER_MINGW_DIR names the mingw prefix passed as --sysroot");
Check(tc.mingwPrefix == "/opt/mingw", "CRAFTER_MINGW_DIR names the mingw prefix");
in.env["CRAFTER_MINGW_DIR"] = "mingw";
Check(ResolveToolchain(in).mingwPrefix == fs::absolute("mingw"), "a relative CRAFTER_MINGW_DIR is resolved against the working directory once, when the toolchain is");
}
{
// Sandboxed, the host's /usr stands in for the missing mingw-w64,
@ -153,11 +155,11 @@ int main() {
fs::remove_all(host);
ToolchainInputs in;
in.hostRoot = host;
Check(ResolveToolchain(in).mingwSysroot.empty(), "a host without mingw-w64 gives no --sysroot");
Check(ResolveToolchain(in).mingwPrefix.empty(), "a host without mingw-w64 gives no mingw prefix");
fs::create_directories(host / "usr" / "x86_64-w64-mingw32");
Check(ResolveToolchain(in).mingwSysroot == host / "usr", "a host with mingw-w64 gives its /usr as the mingw prefix");
Check(ResolveToolchain(in).mingwPrefix == host / "usr", "a host with mingw-w64 gives its /usr as the mingw prefix");
in.env["CRAFTER_MINGW_DIR"] = "/opt/mingw";
Check(ResolveToolchain(in).mingwSysroot == "/opt/mingw", "CRAFTER_MINGW_DIR wins over the host's");
Check(ResolveToolchain(in).mingwPrefix == "/opt/mingw", "CRAFTER_MINGW_DIR wins over the host's");
fs::remove_all(host);
}
{