[PATCH] D11191: unwind: Export _Unwind_{Get, Set}{GR, IP}() for ARM EHABI.

[Logan Chien]

logan created this revision.
logan added reviewers: rengolin, joerg, danalbert, asl, compnerd.
logan added a subscriber: cfe-commits.
logan added a dependency: D11190: unwind: Fix libc++abi and libgcc build..
Herald added subscribers: rengolin, aemerson.

I have removed the exported symbols of _Unwind_{Get,Set}{GR,IP}()
from libunwind.so in D11190.  However, it is debatable whether we should
export those symbols.  Thus, I am uploading this patch for discussion.

Arguments for this patch:

* The programs that do not include <unwind.h> and declares their own
  function declarations can still be linked with our libunwind.so.

* _Unwind_{Get,Set}{GR,IP}() are listed in C++ Itanium Level 1 unwinding API.

Arguments against this patch:

* libgcc does not provide these symbols at all.  We should not extend the ABI
  without deliberate consideration.

* Programs that didn't include <unwind.h> deserves not being compiled.  If the
  application developers have tried to port their code to ARM, they should
  already found the problem.

* ARM EHABI only specified _Unwind_VRS_{Get,Set}() for such purpose.

I personally against this patch, but I would like to see if there are other
comments/concerns.

Depends on D11190

http://reviews.llvm.org/D11191

Files:
  include/unwind.h
  src/UnwindLevel1.c

Index: src/UnwindLevel1.c
===================================================================
--- src/UnwindLevel1.c
+++ src/UnwindLevel1.c
@@ -12,6 +12,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+// ARM EHABI does not specify _Unwind_{Get,Set}{GR,IP}().  Thus, we are
+// defining inline functions to delegate the function calls to
+// _Unwind_VRS_{Get,Set}().  However, some applications might declare the
+// function protetype directly (instead of including <unwind.h>), thus we need
+// to export these functions in libunwind.so as well.
+#define __LIBUNWIND_DONT_INLINE_UNWIND_LEVEL1 1
+
 #include <inttypes.h>
 #include <stdint.h>
 #include <stdbool.h>
Index: include/unwind.h
===================================================================
--- include/unwind.h
+++ include/unwind.h
@@ -214,32 +214,40 @@
 
 #else  // LIBCXXABI_ARM_EHABI
 
+#if !defined(__LIBUNWIND_DONT_INLINE_UNWIND_LEVEL1)
+#define __LIBUNWIND_EXPORT_UNWIND_LEVEL1 static __inline__
+#else
+#define __LIBUNWIND_EXPORT_UNWIND_LEVEL1 extern
+#endif
+
 // These are de facto helper functions for ARM, which delegate the function
 // calls to _Unwind_VRS_Get/Set().  These are not a part of ARM EHABI
 // specification, thus these function MUST be inlined.  Please don't replace
 // these with the "extern" functin declaration; otherwise, the program
 // including this <unwind.h> header won't be ABI compatible and will result in
 // link error when we are linking the program with libgcc.
 
-static __inline__ uintptr_t _Unwind_GetGR(struct _Unwind_Context *context,
-                                          int index) {
+__LIBUNWIND_EXPORT_UNWIND_LEVEL1
+uintptr_t _Unwind_GetGR(struct _Unwind_Context *context, int index) {
   uintptr_t value = 0;
   _Unwind_VRS_Get(context, _UVRSC_CORE, (uint32_t)index, _UVRSD_UINT32, &value);
   return value;
 }
 
-static __inline__ void _Unwind_SetGR(struct _Unwind_Context *context,
-                                     int index, uintptr_t value) {
+__LIBUNWIND_EXPORT_UNWIND_LEVEL1
+void _Unwind_SetGR(struct _Unwind_Context *context, int index,
+                   uintptr_t value) {
   _Unwind_VRS_Set(context, _UVRSC_CORE, (uint32_t)index, _UVRSD_UINT32, &value);
 }
 
-static __inline__ uintptr_t _Unwind_GetIP(struct _Unwind_Context *context) {
+__LIBUNWIND_EXPORT_UNWIND_LEVEL1
+uintptr_t _Unwind_GetIP(struct _Unwind_Context *context) {
   // remove the thumb-bit before returning
   return _Unwind_GetGR(context, 15) & (~(uintptr_t)0x1);
 }
 
-static __inline__ void _Unwind_SetIP(struct _Unwind_Context *context,
-                                     uintptr_t value) {
+__LIBUNWIND_EXPORT_UNWIND_LEVEL1
+void _Unwind_SetIP(struct _Unwind_Context *context, uintptr_t value) {
   uintptr_t thumb_bit = _Unwind_GetGR(context, 15) & ((uintptr_t)0x1);
   _Unwind_SetGR(context, 15, value | thumb_bit);
 }


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