[clang] [compiler-rt] [UBSan] Fix incorrect alignment reported when global new returns an o… (PR #152532)

[via llvm-commits]

================
@@ -1749,17 +1739,29 @@ llvm::Value *CodeGenFunction::EmitCXXNewExpr(const CXXNewExpr *E) {
       allocator->isReservedGlobalPlacementOperator())
     result = Builder.CreateLaunderInvariantGroup(result);
 
+  // Check what type of constructor call the sanitizer is checking
+  // Different UB can occour with custom overloads of operator new
+  TypeCheckKind checkKind = CodeGenFunction::TCK_ConstructorCall;
+  const TargetInfo &TI = getContext().getTargetInfo();
+  unsigned DefaultTargetAlignment = TI.getNewAlign() / TI.getCharWidth();
+  SourceManager &SM = getContext().getSourceManager();
+  SourceLocation Loc = E->getOperatorNew()->getLocation();
+  bool IsCustomOverload = !SM.isInSystemHeader(Loc);
----------------
gbMattN wrote:

If new somehow returns bad alignment without it being a user overload, it will still be caught with the regular constructor-on error. The new error adds information specific to cases when a user has erroneously returned a smaller than allowed alignment in their overload, so I thought it best to only emit the new error in those cases. I can certainly remove some of these checks if its too overcomplicated though.

And do you mind explaining your second point some more? I don't understand it yet!

https://github.com/llvm/llvm-project/pull/152532