[clang] [clang-tools-extra] [llvm] [LLVM][CLANG] Update signal-handling behavior to comply with POSIX (PR #169340)

[David Tenty via cfe-commits]

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@@ -99,8 +99,16 @@ using SignalHandlerCallback = void (*)(void *);
 
 /// Add a function to be called when an abort/kill signal is delivered to the
 /// process. The handler can have a cookie passed to it to identify what
-/// instance of the handler it is.
+/// instance of the handler it is. On Unix systems, the
+/// NeedsPOSIXUtilitySignalHandling argument indicates whether POSIX signal
+/// handling semantics are followed, so that the signal handler resignals
+/// itself to terminate after handling the signal.
+#ifdef _WIN32
 LLVM_ABI void AddSignalHandler(SignalHandlerCallback FnPtr, void *Cookie);
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daltenty wrote:

Since this function is external ABI facing, I'm inclined to say the interface should be the same on all platforms (even if the additional param is a no-op for non-UNIX targets) or the user code will have to handle the difference.

https://github.com/llvm/llvm-project/pull/169340