[clang] [analyzer] Fix false double free when including 3rd-party headers with overloaded delete operator as system headers (PR #85224)

[Balazs Benics via cfe-commits]

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@@ -1090,7 +1090,8 @@ static bool isStandardNewDelete(const FunctionDecl *FD) {
   // If the header for operator delete is not included, it's still defined
   // in an invalid source location. Check to make sure we don't crash.
   return !L.isValid() ||
-         FD->getASTContext().getSourceManager().isInSystemHeader(L);
+         (!FD->hasBody() && // FIXME: Still a false alarm after CTU inlining.
+          FD->getASTContext().getSourceManager().isInSystemHeader(L));
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steakhal wrote:

This check still has some problems.
`FD` is not guaranteed to be the function decl which has the body, thus consequently, the location of `FD` might not point to the definition, even if FD has a definition.

`FD` likely points to the last decl declaration spelling.
I didn't have time to publish my extra tests demonstrating this, but I'll come back to this.

https://github.com/llvm/llvm-project/pull/85224