================
@@ -15383,6 +15401,31 @@ static void diagnoseDeprecatedCopyOperation(Sema &S,
CXXMethodDecl *CopyOp) {
}
}
+// A defaulted copy or move assignment operator for a union copies the object
+// representation as if by a memcpy, the same way the defaulted union copy
+// constructor does. The memberwise loops in DefineImplicitCopyAssignment and
+// DefineImplicitMoveAssignment skip union members, so the whole-object copy is
+// emitted here instead. Marks AssignOp invalid and returns false on failure.
+static bool buildUnionAssignmentCopy(Sema &S, SourceLocation Loc,
+ CXXRecordDecl *ClassDecl,
+ std::optional<RefBuilder> &ExplicitObject,
+ std::optional<DerefBuilder> &DerefThis,
+ const ExprBuilder &From,
+ CXXMethodDecl *AssignOp,
+ SmallVectorImpl<Stmt *> &Statements) {
+ ExprBuilder &To = ExplicitObject ? static_cast<ExprBuilder
&>(*ExplicitObject)
+ : static_cast<ExprBuilder &>(*DerefThis);
+ StmtResult Copy = buildMemcpyForAssignmentOp(
----------------
erichkeane wrote:
> > No, I don't think we should be messing with the 'CheckMemaccessArguments'
> > bit either. I suspect the solution is for `DiagRuntimeBehavior ` to be
> > taught to pay attention to whether the warning it is trying to emit is
> > ignored. WDYT @AaronBallman ?
>
> I think more debugging is needed -- the diagnostic engine is what decides to
> skip rendering an ignored diagnostic:
>
> https://github.com/llvm/llvm-project/blob/01891953eea17544f6181bb51c973711a382702b/clang/lib/Basic/Diagnostic.cpp#L676
> so why is that logic not working?
>
> > ... which in a potentially-evaluated context defers it via DiagIfReachable
> > into the function scope's PossiblyUnreachableDiags. Those flush only when
> > ~SynthesizedFunctionScope runs PopFunctionScopeInfo at the end of the
> > synthesized body. The ignore state is read at that flush rather than at the
> > call. S
>
> It makes sense that we process those when popping the function scope, but why
> is the location of the diagnostics incorrect? I can't seem to induce a
> failure through using the pragma directly: https://godbolt.org/z/T31b1T8f1
`SetIgnoreAllWarnings` doesn't actually modify the 'loc' info of the diagnostic
being enabled. It is just a little bit of a side-channel disable for warnings.
So it only applys at the actual 'When emitted' time of the compiler, not of
the location in source. So it is a bit 'hacked' in like I said above.
To do the 'source based' bit, we'd have to do the `setSeverity` type calls, and
doing that for all warnings every time we do a union seems like a 'heavy' lift?
https://github.com/llvm/llvm-project/pull/206579
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