[clang] [llvm] [LLVM][Clang][Cygwin] Fix building Clang for Cygwin (PR #134494)

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@@ -847,7 +847,11 @@ void llvm::sys::PrintStackTrace(raw_ostream &OS, int Depth) {
 
     const char *name = strrchr(dlinfo.dli_fname, '/');
     if (!name)
+#ifdef __CYGWIN__
+      OS << format(" %-*s", width, &dlinfo.dli_fname);
----------------
jeremyd2019 wrote:

> Can we even trust Cygwin's `dli_fname` to always be null terminated?

Yes.  It calls cygwin_conv_path to fill it, and cygwin_conv_path will set `ENOSPC` and not touch the buffer if it's not big enough.  If cygwin_conv_path fails dladdr will return 0.

https://github.com/llvm/llvm-project/pull/134494