[PATCH] D121927: [Clang] Work with multiple pragmas weak before definition

[Hubert Tong via Phabricator via cfe-commits]

hubert.reinterpretcast marked an inline comment as done.
hubert.reinterpretcast added inline comments.


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Comment at: clang/include/clang/Sema/Weak.h:62
+        return false;
+      return LHS.getAlias()->getName() == RHS.getAlias()->getName();
+    }
----------------
aaron.ballman wrote:
> Previously we cared about the source locations being the same. But... is there a situation where the aliases are the same but the source locations are different? I can't think of any, so perhaps that's worth an assert that the locations match?
We didn't really case about the source locations being the same. The removed operators were just dead code (featuring such things as compare-by-pointer-value). I have verified that splitting the deletion of them to a separate patch does not cause any build or LIT `check-all` failures. I can commit that part as an NFC patch first if you prefer.

Also, the aliases //can// be the same with different source locations. The location comes from where the `#pragma weak` is (from the parser by way of `ActOnPragmaWeakAlias`). That duplicates are ignored (meaning we only diagnose one instance) is mentioned in the patch description.

It is already the status quo that having the same alias specified with different targets (at least those not yet declared) neither produces a diagnostic nor operates by "last one wins". Instead, Clang prefers the first declared target and GCC just emits both and leaves it to the assembler to figure out (https://godbolt.org/z/EasK375j3).


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https://reviews.llvm.org/D121927