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Rollup merge of #119587 - beepster4096:system_varargs, r=petrochenkov

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Varargs support for system ABI

This PR allows functions with the `system` ABI to be variadic (under the `extended_varargs_abi_support` feature tracked in #100189). On x86 windows, the `system` ABI is equivalent to `C` for variadic functions. On other platforms, `system` is already equivalent to `C`.

Fixes #110505
This commit is contained in:
Matthias Krüger 2024-01-13 15:10:28 +01:00 • committed by GitHub
commit 7b507db24b
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8 changed files with 34 additions and 13 deletions
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8
compiler/rustc_target/src/spec/mod.rs
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@ -2401,10 +2401,14 @@ impl DerefMut for Target {
impl Target {
/// Given a function ABI, turn it into the correct ABI for this target.
pub fn adjust_abi(&self, abi: Abi) -> Abi {
pub fn adjust_abi(&self, abi: Abi, c_variadic: bool) -> Abi {
match abi {
Abi::C { .. } => self.default_adjusted_cabi.unwrap_or(abi),
Abi::System { unwind } if self.is_like_windows && self.arch == "x86" => {
// On Windows, `extern "system"` behaves like msvc's `__stdcall`.
// `__stdcall` only applies on x86 and on non-variadic functions:
// https://learn.microsoft.com/en-us/cpp/cpp/stdcall?view=msvc-170
Abi::System { unwind } if self.is_like_windows && self.arch == "x86" && !c_variadic => {
Abi::Stdcall { unwind }
}
Abi::System { unwind } => Abi::C { unwind },