================
@@ -1749,17 +1751,32 @@ llvm::Value *CodeGenFunction::EmitCXXNewExpr(const
CXXNewExpr *E) {
allocator->isReservedGlobalPlacementOperator())
result = Builder.CreateLaunderInvariantGroup(result);
+ // Check the default alignment of the type and why. Users may incorrectly
+ // return misaligned memory from a replaced operator new without knowing
+ // about default alignment.
+ TypeCheckKind checkKind = CodeGenFunction::TCK_ConstructorCall;
+ CharUnits checkAlignment = result.getAlignment();
+ const TargetInfo &TI = getContext().getTargetInfo();
+ unsigned DefaultTargetAlignment = TI.getNewAlign() / TI.getCharWidth();
+ if (SanOpts.has(SanitizerKind::Alignment) &&
+ (DefaultTargetAlignment >
+ CGM.getContext().getTypeAlignInChars(allocType).getQuantity()) &&
+ !result.getAlignment().isOne() &&
----------------
gbMattN wrote:
Its an imperfect check, I've spent some time trying to find something better.
Its all for the sake of this case in the clang test catch-undef-behaviour:
```
// CHECK-LABEL: define{{.*}}throwing_new_zero_size
void *throwing_new_zero_size() {
// Nothing to check here.
// CHECK-NOT: __ubsan_handle_type_mismatch
return new (nothrow{}) char[0];
// CHECK: ret
}
}
```
afaik, a nothrow char array of size 0 is an exception to the undefined
behaviour. All I added was the isOne check as it made the test pass, but since
looking into the matter further its too broad an exception.
https://github.com/llvm/llvm-project/pull/166755
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