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Fix LLVM IR generated for C-variadic arguments #59577

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Merged
merged 1 commit into from
Mar 31, 2019
Merged

Fix LLVM IR generated for C-variadic arguments #59577

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15 changes: 2 additions & 13 deletions src/librustc_codegen_ssa/mir/block.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ use syntax_pos::Pos;

use super::{FunctionCx, LocalRef};
use super::place::PlaceRef;
use super::operand::{OperandValue, OperandRef};
use super::operand::OperandRef;
use super::operand::OperandValue::{Pair, Ref, Immediate};

/// Used by `FunctionCx::codegen_terminator` for emitting common patterns
Expand Down Expand Up @@ -695,18 +695,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
// an "spoofed" `VaList`. This argument is ignored, but we need to
// populate it with a dummy operand so that the users real arguments
// are not overwritten.
let i = if sig.c_variadic && last_arg_idx.map(|x| x == i).unwrap_or(false) {
let layout = match self.cx.tcx().lang_items().va_list() {
Some(did) => bx.cx().layout_of(bx.tcx().type_of(did)),
None => bug!("`va_list` language item required for C-variadics"),
};
let op = OperandRef {
val: OperandValue::Immediate(
bx.cx().const_undef(bx.cx().immediate_backend_type(layout)
)),
layout: layout,
};
self.codegen_argument(&mut bx, op, &mut llargs, &fn_ty.args[i]);
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codegen_argument when called given a function where is_ignore is true doesn't do anything other than add padding (which we shouldn't do here for C-variadics), so this section isn't needed.

let i = if sig.c_variadic && last_arg_idx.map(|x| i >= x).unwrap_or(false) {
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If we hit the "spoofed" C-variadic argument we need to use i + 1 for each of the subsequent iterations of this loop. If we don't we'll end up using the wrong argument info.

if i + 1 < fn_ty.args.len() {
i + 1
} else {
Expand Down
21 changes: 21 additions & 0 deletions src/test/codegen/issue-58881.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
// compile-flags: -C no-prepopulate-passes
//
// only-x86_64
// ignore-windows

#![crate_type = "lib"]

extern "C" {
fn variadic_fn(_: i32, ...);
}

#[repr(C)]
struct Foo(u8);
#[repr(C)]
struct Bar(u64, u64, u64);

// Ensure that emit arguments of the correct type.
pub unsafe fn test_call_variadic() {
// CHECK: call void (i32, ...) @variadic_fn(i32 0, i8 {{.*}}, %Bar* {{.*}})
variadic_fn(0, Foo(0), Bar(0, 0, 0))
}