unwind.h fix for -fvisibility=hidden users. This fixes firefox build in a system
with libunwind installed.
Patch by Jeffrey Yasskin!
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@153633 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Headers/unwind.h b/lib/Headers/unwind.h
index a99c8a1..a065920 100644
--- a/lib/Headers/unwind.h
+++ b/lib/Headers/unwind.h
@@ -31,7 +31,19 @@
# define _SHOULD_UNDEFINE_GNU_SOURCE
# define _GNU_SOURCE
# endif
-# include_next <unwind.h>
+// libunwind's unwind.h reflects the current visibility. However, Mozilla
+// builds with -fvisibility=hidden and relies on gcc's unwind.h to reset the
+// visibility to default and export its contents. gcc also allows users to
+// override its override by #defining HIDE_EXPORTS (but note, this only obeys
+// the user's -fvisibility setting; it doesn't hide any exports on its own). We
+// imitate gcc's header here:
+# ifdef HIDE_EXPORTS
+# include_next <unwind.h>
+# else
+# pragma GCC visibility push(default)
+# include_next <unwind.h>
+# pragma GCC visibility pop
+# endif
# ifdef _SHOULD_UNDEFINE_GNU_SOURCE
# undef _GNU_SOURCE
# undef _SHOULD_UNDEFINE_GNU_SOURCE
