Fix llvm-libunwind userspace build on ARM

GCC's libgcc exports a few ARM-specific symbols for ARM EABI, AEABI, or
EHABI or whatever it's called.  Export the same ones from LLVM-libunwind's
libgcc_s, on ARM.  As part of this, convert libgcc_s from a direct
Version.map to one constructed from component Symbol.map files.  This allows
the ARM-specific Symbol.map to be included only on ARM.

Fix ARM-only oddities in struct name/aliases in LLVM-libunwind to match
non-ARM definitions and ARM-specific expectations in libcxxrt /
libcompiler_rt.

No functional change intended for non-ARM architectures.

This commit does not actually flip the switch for ARM defaults from libgcc
to llvm-libunwind, but makes it possible (to compile, anyway).

1 files changed, 16 insertions, 1 deletions

diff --git a/contrib/compiler-rt/lib/builtins/gcc_personality_v0.c b/contrib/compiler-rt/lib/builtins/gcc_personality_v0.c
index d12ee03c49fe..b986bd56943e 100644
--- a/contrib/compiler-rt/lib/builtins/gcc_personality_v0.c
+++ b/contrib/compiler-rt/lib/builtins/gcc_personality_v0.c
@@ -9,8 +9,23 @@
 #include "int_lib.h"
 
 #include <unwind.h>
+/*
+ * XXX On FreeBSD, this file is compiled into three libraries:
+ *   - libcompiler_rt
+ *   - libgcc_eh
+ *   - libgcc_s
+ *
+ * In the former, the include path points to the contrib/libcxxrt/unwind-arm.h
+ * copy of unwind.h.  In the latter, the include path points to the
+ * contrib/libunwind/include/unwind.h header (LLVM libunwind).
+ *
+ * Neither (seemingly redundant) variant of unwind.h needs the redefinitions
+ * provided in the "helpful" header below, and libcxxrt's unwind-arm.h provides
+ * *no* useful distinguishing macros, so just forcibly disable the helper
+ * header on FreeBSD.
+ */
 #if defined(__arm__) && !defined(__ARM_DWARF_EH__) &&                          \
-    !defined(__USING_SJLJ_EXCEPTIONS__)
+    !defined(__USING_SJLJ_EXCEPTIONS__) && !defined(__FreeBSD__)
 // When building with older compilers (e.g. clang <3.9), it is possible that we
 // have a version of unwind.h which does not provide the EHABI declarations
 // which are quired for the C personality to conform to the specification.  In