[llvm] [llvm][StackProtector] Add noreturn to __stack_chk_fail aliassee (PR #143976)

[Eli Friedman via llvm-commits]

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@@ -725,7 +725,9 @@ BasicBlock *CreateFailBB(Function *F, const Triple &Trip) {
     StackChkFail =
         M->getOrInsertFunction("__stack_chk_fail", Type::getVoidTy(Context));
   }
-  cast<Function>(StackChkFail.getCallee())->addFnAttr(Attribute::NoReturn);
+  cast<Function>(
+      cast<GlobalValue>(StackChkFail.getCallee())->getAliaseeObject())
+      ->addFnAttr(Attribute::NoReturn);
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efriedma-quic wrote:

This can also fail, if you try hard enough.

If the global already exists for some reason (`M->getNamedValue("__stack_chk_fail") != nullptr`), we probably shouldn't try to mess with it.  Maybe we can stick a noreturn attribute on the call instead.

https://github.com/llvm/llvm-project/pull/143976