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build: default bindgen to gnu11 #27

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6983b93
build: default bindgen to gnu11
alex-semenyuk Mar 14, 2026
e8b5be0
bindgen: force C11 atomics and avoid x86 intrinsics on non-x86
alex-semenyuk Mar 15, 2026
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32 changes: 32 additions & 0 deletions Modules/cpython-sys/build.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,8 @@ fn generate_c_api_bindings(srcdir: &Path, builddir: Option<&str>, out_path: &Pat

// Suppress all clang warnings (deprecation warnings, etc.)
builder = builder.clang_arg("-w");
// Force C mode for CPython headers.
builder = builder.clang_arg("-x").clang_arg("c");

// Tell clang the correct target triple for cross-compilation when we have
// an LLVM-specific triple. Otherwise let bindgen translate Cargo's TARGET
Expand All @@ -80,6 +82,7 @@ fn generate_c_api_bindings(srcdir: &Path, builddir: Option<&str>, out_path: &Pat
// - WASI: sysroot in CC, -D_WASI_EMULATED_SIGNAL in CFLAGS
// - iOS: -isysroot in CPPFLAGS
let mut have_sysroot = false;
let mut std_flag: Option<String> = None;
for env_name in ["PY_CC", "PY_CPPFLAGS", "PY_CFLAGS"] {
if let Ok(value) = env::var(env_name)
&& let Some(flags) = shlex::split(&value)
Expand All @@ -95,16 +98,45 @@ fn generate_c_api_bindings(srcdir: &Path, builddir: Option<&str>, out_path: &Pat
{
builder = builder.clang_arg(path);
}
} else if flag == "-std" {
builder = builder.clang_arg(flag);
if let Some(value) = iter.next() {
builder = builder.clang_arg(value);
std_flag = Some(value.to_string());
}
} else if flag.starts_with("-I")
|| flag.starts_with("-D")
|| flag.starts_with("-std=")
|| flag.starts_with("-isystem")
{
builder = builder.clang_arg(flag);
if flag.starts_with("-std=") {
std_flag = Some(flag.trim_start_matches("-std=").to_string());
}
}
}
}
}
let needs_c11 = match std_flag.as_deref() {
None => true,
Some("c89" | "c90" | "c99" | "gnu89" | "gnu90" | "gnu99") => true,
_ => false,
};
if needs_c11 {
// Bindgen needs C11 for stdatomic.h (e.g. mimalloc); override older defaults.
builder = builder.clang_arg("-std=gnu11");
}
// Bindgen parses headers only; force C11 atomics to be available even if
// the target's std headers disable them in freestanding mode.
builder = builder
.clang_arg("-U__STDC_NO_ATOMICS__")
.clang_arg("-D__STDC_NO_ATOMICS__=0")
.clang_arg("-D__STDC_HOSTED__=1");
// Avoid x86 intrinsic headers on non-x86 targets (they can error in clang's
// builtin headers when the target/sysroot doesn't match).
if !cargo_target.contains("x86_64") && !cargo_target.contains("i686") && !cargo_target.contains("x86") {
builder = builder.clang_arg("-U__SSE2__").clang_arg("-U__MMX__");
}

// WASI SDK: WASI_SDK_PATH is set by Tools/wasm/wasi/__main__.py.
// The sysroot is at $WASI_SDK_PATH/share/wasi-sysroot.
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