libunwind/src/UnwindLevel1-gcc-ext.c - third_party/llvm-project - Git at Google

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //
 //  Implements gcc extensions to the C++ ABI Exception Handling Level 1.
 //
 //===----------------------------------------------------------------------===//

 #include <inttypes.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

 #include "config.h"
 #include "libunwind_ext.h"
 #include "libunwind.h"
 #include "Unwind-EHABI.h"
 #include "unwind.h"

 #if defined(_AIX)
 #include <sys/debug.h>
 #endif

 #if defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)

 #if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
 #define PRIVATE_1 private_[0]
 #elif defined(_LIBUNWIND_ARM_EHABI)
 #define PRIVATE_1 unwinder_cache.reserved1
 #else
 #define PRIVATE_1 private_1
 #endif

 ///  Called by __cxa_rethrow().
 _LIBUNWIND_EXPORT _Unwind_Reason_Code
 _Unwind_Resume_or_Rethrow(_Unwind_Exception *exception_object) {
   _LIBUNWIND_TRACE_API(
       "_Unwind_Resume_or_Rethrow(ex_obj=%p), private_1=%" PRIdPTR,
       (void *)exception_object, (intptr_t)exception_object->PRIVATE_1);

   // If this is non-forced and a stopping place was found, then this is a
   // re-throw.
   // Call _Unwind_RaiseException() as if this was a new exception
   if (exception_object->PRIVATE_1 == 0) {
     return _Unwind_RaiseException(exception_object);
     // Will return if there is no catch clause, so that __cxa_rethrow can call
     // std::terminate().
   }

   // Call through to _Unwind_Resume() which distinguishes between forced and
   // regular exceptions.
   _Unwind_Resume(exception_object);
   _LIBUNWIND_ABORT("_Unwind_Resume_or_Rethrow() called _Unwind_RaiseException()"
                    " which unexpectedly returned");
 }

 /// Called by personality handler during phase 2 to get base address for data
 /// relative encodings.
 _LIBUNWIND_EXPORT uintptr_t
 _Unwind_GetDataRelBase(struct _Unwind_Context *context) {
   _LIBUNWIND_TRACE_API("_Unwind_GetDataRelBase(context=%p)", (void *)context);
 #if defined(_AIX)
   return unw_get_data_rel_base((unw_cursor_t *)context);
 #else
   (void)context;
   _LIBUNWIND_ABORT("_Unwind_GetDataRelBase() not implemented");
 #endif
 }

 /// Called by personality handler during phase 2 to get base address for text
 /// relative encodings.
 _LIBUNWIND_EXPORT uintptr_t
 _Unwind_GetTextRelBase(struct _Unwind_Context *context) {
   (void)context;
   _LIBUNWIND_TRACE_API("_Unwind_GetTextRelBase(context=%p)", (void *)context);
   _LIBUNWIND_ABORT("_Unwind_GetTextRelBase() not implemented");
 }


 /// Scans unwind information to find the function that contains the
 /// specified code address "pc".
 _LIBUNWIND_EXPORT void *_Unwind_FindEnclosingFunction(void *pc) {
   _LIBUNWIND_TRACE_API("_Unwind_FindEnclosingFunction(pc=%p)", pc);
 #if defined(_AIX)
   if (pc == NULL)
     return NULL;

   // Get the start address of the enclosing function from the function's
   // traceback table.
   uint32_t *p = (uint32_t *)pc;

   // Keep looking forward until a word of 0 is found. The traceback
   // table starts at the following word.
   while (*p)
     ++p;
   struct tbtable *TBTable = (struct tbtable *)(p + 1);

   // Get the address of the traceback table extension.
   p = (uint32_t *)&TBTable->tb_ext;

   // Skip field parminfo if it exists.
   if (TBTable->tb.fixedparms || TBTable->tb.floatparms)
     ++p;

   if (TBTable->tb.has_tboff)
     // *p contains the offset from the function start to traceback table.
     return (void *)((uintptr_t)TBTable - *p - sizeof(uint32_t));
   return NULL;
 #else
   // This is slow, but works.
   // We create an unwind cursor then alter the IP to be pc
   unw_cursor_t cursor;
   unw_context_t uc;
   unw_proc_info_t info;
   __unw_getcontext(&uc);
   __unw_init_local(&cursor, &uc);
   __unw_set_reg(&cursor, UNW_REG_IP, (unw_word_t)(intptr_t)pc);
   if (__unw_get_proc_info(&cursor, &info) == UNW_ESUCCESS)
     return (void *)(intptr_t) info.start_ip;
   else
     return NULL;
 #endif
 }

 /// Walk every frame and call trace function at each one.  If trace function
 /// returns anything other than _URC_NO_REASON, then walk is terminated.
 _LIBUNWIND_EXPORT _Unwind_Reason_Code
 _Unwind_Backtrace(_Unwind_Trace_Fn callback, void *ref) {
   unw_cursor_t cursor;
   unw_context_t uc;
   __unw_getcontext(&uc);
   __unw_init_local(&cursor, &uc);

   _LIBUNWIND_TRACE_API("_Unwind_Backtrace(callback=%p)",
                        (void *)(uintptr_t)callback);

 #if defined(_LIBUNWIND_ARM_EHABI)
   // Create a mock exception object for force unwinding.
   _Unwind_Exception ex;
   memset(&ex, '\0', sizeof(ex));
   memcpy(&ex.exception_class, "CLNGUNW", sizeof(ex.exception_class));
 #endif

   // walk each frame
   while (true) {
     _Unwind_Reason_Code result;

 #if !defined(_LIBUNWIND_ARM_EHABI)
     // ask libunwind to get next frame (skip over first frame which is
     // _Unwind_Backtrace())
     if (__unw_step(&cursor) <= 0) {
       _LIBUNWIND_TRACE_UNWINDING(" _backtrace: ended because cursor reached "
                                  "bottom of stack, returning %d",
                                  _URC_END_OF_STACK);
       return _URC_END_OF_STACK;
     }
 #else
     // Get the information for this frame.
     unw_proc_info_t frameInfo;
     if (__unw_get_proc_info(&cursor, &frameInfo) != UNW_ESUCCESS) {
       return _URC_END_OF_STACK;
     }

     // Update the pr_cache in the mock exception object.
     uint32_t *unwindInfo = (uint32_t *)frameInfo.unwind_info;
     ex.pr_cache.fnstart = frameInfo.start_ip;
     ex.pr_cache.ehtp = (_Unwind_EHT_Header *) unwindInfo;
     ex.pr_cache.additional= frameInfo.flags;

     struct _Unwind_Context *context = (struct _Unwind_Context *)&cursor;
     // Get and call the personality function to unwind the frame.
     _Unwind_Personality_Fn handler = (_Unwind_Personality_Fn)frameInfo.handler;
     if (handler == NULL) {
       return _URC_END_OF_STACK;
     }
     if (handler(_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND, &ex, context) !=
             _URC_CONTINUE_UNWIND) {
       return _URC_END_OF_STACK;
     }
 #endif // defined(_LIBUNWIND_ARM_EHABI)

     // debugging
     if (_LIBUNWIND_TRACING_UNWINDING) {
       char functionName[512];
       unw_proc_info_t frame;
       unw_word_t offset;
       __unw_get_proc_name(&cursor, functionName, 512, &offset);
       __unw_get_proc_info(&cursor, &frame);
       _LIBUNWIND_TRACE_UNWINDING(
           " _backtrace: start_ip=0x%" PRIxPTR ", func=%s, lsda=0x%" PRIxPTR ", context=%p",
           frame.start_ip, functionName, frame.lsda,
           (void *)&cursor);
     }

     // call trace function with this frame
     result = (*callback)((struct _Unwind_Context *)(&cursor), ref);
     if (result != _URC_NO_REASON) {
       _LIBUNWIND_TRACE_UNWINDING(
           " _backtrace: ended because callback returned %d", result);
       return result;
     }
   }
 }


 /// Find DWARF unwind info for an address 'pc' in some function.
 _LIBUNWIND_EXPORT const void *_Unwind_Find_FDE(const void *pc,
                                                struct dwarf_eh_bases *bases) {
   // This is slow, but works.
   // We create an unwind cursor then alter the IP to be pc
   unw_cursor_t cursor;
   unw_context_t uc;
   unw_proc_info_t info;
   __unw_getcontext(&uc);
   __unw_init_local(&cursor, &uc);
   __unw_set_reg(&cursor, UNW_REG_IP, (unw_word_t)(intptr_t)pc);
   __unw_get_proc_info(&cursor, &info);
   bases->tbase = (uintptr_t)info.extra;
   bases->dbase = 0; // dbase not used on Mac OS X
   bases->func = (uintptr_t)info.start_ip;
   _LIBUNWIND_TRACE_API("_Unwind_Find_FDE(pc=%p) => %p", pc,
                   (void *)(intptr_t) info.unwind_info);
   return (void *)(intptr_t) info.unwind_info;
 }

 /// Returns the CFA (call frame area, or stack pointer at start of function)
 /// for the current context.
 _LIBUNWIND_EXPORT uintptr_t _Unwind_GetCFA(struct _Unwind_Context *context) {
   unw_cursor_t *cursor = (unw_cursor_t *)context;
   unw_word_t result;
   __unw_get_reg(cursor, UNW_REG_SP, &result);
   _LIBUNWIND_TRACE_API("_Unwind_GetCFA(context=%p) => 0x%" PRIxPTR,
                        (void *)context, result);
   return (uintptr_t)result;
 }


 /// Called by personality handler during phase 2 to get instruction pointer.
 /// ipBefore is a boolean that says if IP is already adjusted to be the call
 /// site address.  Normally IP is the return address.
 _LIBUNWIND_EXPORT uintptr_t _Unwind_GetIPInfo(struct _Unwind_Context *context,
                                               int *ipBefore) {
   _LIBUNWIND_TRACE_API("_Unwind_GetIPInfo(context=%p)", (void *)context);
   int isSignalFrame = __unw_is_signal_frame((unw_cursor_t *)context);
   // Negative means some kind of error (probably UNW_ENOINFO), but we have no
   // good way to report that, and this maintains backward compatibility with the
   // implementation that hard-coded zero in every case, even signal frames.
   if (isSignalFrame <= 0)
     *ipBefore = 0;
   else
     *ipBefore = 1;
   return _Unwind_GetIP(context);
 }

 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)

 /// Called by programs with dynamic code generators that want
 /// to register a dynamically generated FDE.
 /// This function has existed on Mac OS X since 10.4, but
 /// was broken until 10.6.
 _LIBUNWIND_EXPORT void __register_frame(const void *fde) {
   _LIBUNWIND_TRACE_API("__register_frame(%p)", fde);
   __unw_add_dynamic_fde((unw_word_t)(uintptr_t)fde);
 }


 /// Called by programs with dynamic code generators that want
 /// to unregister a dynamically generated FDE.
 /// This function has existed on Mac OS X since 10.4, but
 /// was broken until 10.6.
 _LIBUNWIND_EXPORT void __deregister_frame(const void *fde) {
   _LIBUNWIND_TRACE_API("__deregister_frame(%p)", fde);
   __unw_remove_dynamic_fde((unw_word_t)(uintptr_t)fde);
 }


 // The following register/deregister functions are gcc extensions.
 // They have existed on Mac OS X, but have never worked because Mac OS X
 // before 10.6 used keymgr to track known FDEs, but these functions
 // never got updated to use keymgr.
 // For now, we implement these as do-nothing functions to keep any existing
 // applications working.  We also add the not in 10.6 symbol so that nwe
 // application won't be able to use them.

 #if defined(_LIBUNWIND_SUPPORT_FRAME_APIS)
 _LIBUNWIND_EXPORT void __register_frame_info_bases(const void *fde, void *ob,
                                                    void *tb, void *db) {
   (void)fde;
   (void)ob;
   (void)tb;
   (void)db;
  _LIBUNWIND_TRACE_API("__register_frame_info_bases(%p,%p, %p, %p)",
                             fde, ob, tb, db);
   // do nothing, this function never worked in Mac OS X
 }

 _LIBUNWIND_EXPORT void __register_frame_info(const void *fde, void *ob) {
   (void)fde;
   (void)ob;
   _LIBUNWIND_TRACE_API("__register_frame_info(%p, %p)", fde, ob);
   // do nothing, this function never worked in Mac OS X
 }

 _LIBUNWIND_EXPORT void __register_frame_info_table_bases(const void *fde,
                                                          void *ob, void *tb,
                                                          void *db) {
   (void)fde;
   (void)ob;
   (void)tb;
   (void)db;
   _LIBUNWIND_TRACE_API("__register_frame_info_table_bases"
                              "(%p,%p, %p, %p)", fde, ob, tb, db);
   // do nothing, this function never worked in Mac OS X
 }

 _LIBUNWIND_EXPORT void __register_frame_info_table(const void *fde, void *ob) {
   (void)fde;
   (void)ob;
   _LIBUNWIND_TRACE_API("__register_frame_info_table(%p, %p)", fde, ob);
   // do nothing, this function never worked in Mac OS X
 }

 _LIBUNWIND_EXPORT void __register_frame_table(const void *fde) {
   (void)fde;
   _LIBUNWIND_TRACE_API("__register_frame_table(%p)", fde);
   // do nothing, this function never worked in Mac OS X
 }

 _LIBUNWIND_EXPORT void *__deregister_frame_info(const void *fde) {
   (void)fde;
   _LIBUNWIND_TRACE_API("__deregister_frame_info(%p)", fde);
   // do nothing, this function never worked in Mac OS X
   return NULL;
 }

 _LIBUNWIND_EXPORT void *__deregister_frame_info_bases(const void *fde) {
   (void)fde;
   _LIBUNWIND_TRACE_API("__deregister_frame_info_bases(%p)", fde);
   // do nothing, this function never worked in Mac OS X
   return NULL;
 }
 #endif // defined(_LIBUNWIND_SUPPORT_FRAME_APIS)

 #endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)

 #endif // defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)
	//===----------------------------------------------------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//
	// Implements gcc extensions to the C++ ABI Exception Handling Level 1.
	//
	//===----------------------------------------------------------------------===//

	#include <inttypes.h>
	#include <stdbool.h>
	#include <stdint.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>

	#include "config.h"
	#include "libunwind_ext.h"
	#include "libunwind.h"
	#include "Unwind-EHABI.h"
	#include "unwind.h"

	#if defined(_AIX)
	#include <sys/debug.h>
	#endif

	#if defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)

	#if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
	#define PRIVATE_1 private_[0]
	#elif defined(_LIBUNWIND_ARM_EHABI)
	#define PRIVATE_1 unwinder_cache.reserved1
	#else
	#define PRIVATE_1 private_1
	#endif

	/// Called by __cxa_rethrow().
	_LIBUNWIND_EXPORT _Unwind_Reason_Code
	_Unwind_Resume_or_Rethrow(_Unwind_Exception *exception_object) {
	_LIBUNWIND_TRACE_API(
	"_Unwind_Resume_or_Rethrow(ex_obj=%p), private_1=%" PRIdPTR,
	(void *)exception_object, (intptr_t)exception_object->PRIVATE_1);

	// If this is non-forced and a stopping place was found, then this is a
	// re-throw.
	// Call _Unwind_RaiseException() as if this was a new exception
	if (exception_object->PRIVATE_1 == 0) {
	return _Unwind_RaiseException(exception_object);
	// Will return if there is no catch clause, so that __cxa_rethrow can call
	// std::terminate().
	}

	// Call through to _Unwind_Resume() which distinguishes between forced and
	// regular exceptions.
	_Unwind_Resume(exception_object);
	_LIBUNWIND_ABORT("_Unwind_Resume_or_Rethrow() called _Unwind_RaiseException()"
	" which unexpectedly returned");
	}

	/// Called by personality handler during phase 2 to get base address for data
	/// relative encodings.
	_LIBUNWIND_EXPORT uintptr_t
	_Unwind_GetDataRelBase(struct _Unwind_Context *context) {
	_LIBUNWIND_TRACE_API("_Unwind_GetDataRelBase(context=%p)", (void *)context);
	#if defined(_AIX)
	return unw_get_data_rel_base((unw_cursor_t *)context);
	#else
	(void)context;
	_LIBUNWIND_ABORT("_Unwind_GetDataRelBase() not implemented");
	#endif
	}

	/// Called by personality handler during phase 2 to get base address for text
	/// relative encodings.
	_LIBUNWIND_EXPORT uintptr_t
	_Unwind_GetTextRelBase(struct _Unwind_Context *context) {
	(void)context;
	_LIBUNWIND_TRACE_API("_Unwind_GetTextRelBase(context=%p)", (void *)context);
	_LIBUNWIND_ABORT("_Unwind_GetTextRelBase() not implemented");
	}


	/// Scans unwind information to find the function that contains the
	/// specified code address "pc".
	_LIBUNWIND_EXPORT void _Unwind_FindEnclosingFunction(void pc) {
	_LIBUNWIND_TRACE_API("_Unwind_FindEnclosingFunction(pc=%p)", pc);
	#if defined(_AIX)
	if (pc == NULL)
	return NULL;

	// Get the start address of the enclosing function from the function's
	// traceback table.
	uint32_t p = (uint32_t )pc;

	// Keep looking forward until a word of 0 is found. The traceback
	// table starts at the following word.
	while (*p)
	++p;
	struct tbtable TBTable = (struct tbtable )(p + 1);

	// Get the address of the traceback table extension.
	p = (uint32_t *)&TBTable->tb_ext;

	// Skip field parminfo if it exists.
	if (TBTable->tb.fixedparms \|\| TBTable->tb.floatparms)
	++p;

	if (TBTable->tb.has_tboff)
	// *p contains the offset from the function start to traceback table.
	return (void )((uintptr_t)TBTable - p - sizeof(uint32_t));
	return NULL;
	#else
	// This is slow, but works.
	// We create an unwind cursor then alter the IP to be pc
	unw_cursor_t cursor;
	unw_context_t uc;
	unw_proc_info_t info;
	__unw_getcontext(&uc);
	__unw_init_local(&cursor, &uc);
	__unw_set_reg(&cursor, UNW_REG_IP, (unw_word_t)(intptr_t)pc);
	if (__unw_get_proc_info(&cursor, &info) == UNW_ESUCCESS)
	return (void *)(intptr_t) info.start_ip;
	else
	return NULL;
	#endif
	}

	/// Walk every frame and call trace function at each one. If trace function
	/// returns anything other than _URC_NO_REASON, then walk is terminated.
	_LIBUNWIND_EXPORT _Unwind_Reason_Code
	_Unwind_Backtrace(_Unwind_Trace_Fn callback, void *ref) {
	unw_cursor_t cursor;
	unw_context_t uc;
	__unw_getcontext(&uc);
	__unw_init_local(&cursor, &uc);

	_LIBUNWIND_TRACE_API("_Unwind_Backtrace(callback=%p)",
	(void *)(uintptr_t)callback);

	#if defined(_LIBUNWIND_ARM_EHABI)
	// Create a mock exception object for force unwinding.
	_Unwind_Exception ex;
	memset(&ex, '\0', sizeof(ex));
	memcpy(&ex.exception_class, "CLNGUNW", sizeof(ex.exception_class));
	#endif

	// walk each frame
	while (true) {
	_Unwind_Reason_Code result;

	#if !defined(_LIBUNWIND_ARM_EHABI)
	// ask libunwind to get next frame (skip over first frame which is
	// _Unwind_Backtrace())
	if (__unw_step(&cursor) <= 0) {
	_LIBUNWIND_TRACE_UNWINDING(" _backtrace: ended because cursor reached "
	"bottom of stack, returning %d",
	_URC_END_OF_STACK);
	return _URC_END_OF_STACK;
	}
	#else
	// Get the information for this frame.
	unw_proc_info_t frameInfo;
	if (__unw_get_proc_info(&cursor, &frameInfo) != UNW_ESUCCESS) {
	return _URC_END_OF_STACK;
	}

	// Update the pr_cache in the mock exception object.
	uint32_t unwindInfo = (uint32_t )frameInfo.unwind_info;
	ex.pr_cache.fnstart = frameInfo.start_ip;
	ex.pr_cache.ehtp = (_Unwind_EHT_Header *) unwindInfo;
	ex.pr_cache.additional= frameInfo.flags;

	struct _Unwind_Context context = (struct _Unwind_Context )&cursor;
	// Get and call the personality function to unwind the frame.
	_Unwind_Personality_Fn handler = (_Unwind_Personality_Fn)frameInfo.handler;
	if (handler == NULL) {
	return _URC_END_OF_STACK;
	}
	if (handler(_US_VIRTUAL_UNWIND_FRAME \| _US_FORCE_UNWIND, &ex, context) !=
	_URC_CONTINUE_UNWIND) {
	return _URC_END_OF_STACK;
	}
	#endif // defined(_LIBUNWIND_ARM_EHABI)

	// debugging
	if (_LIBUNWIND_TRACING_UNWINDING) {
	char functionName[512];
	unw_proc_info_t frame;
	unw_word_t offset;
	__unw_get_proc_name(&cursor, functionName, 512, &offset);
	__unw_get_proc_info(&cursor, &frame);
	_LIBUNWIND_TRACE_UNWINDING(
	" _backtrace: start_ip=0x%" PRIxPTR ", func=%s, lsda=0x%" PRIxPTR ", context=%p",
	frame.start_ip, functionName, frame.lsda,
	(void *)&cursor);
	}

	// call trace function with this frame
	result = (callback)((struct _Unwind_Context )(&cursor), ref);
	if (result != _URC_NO_REASON) {
	_LIBUNWIND_TRACE_UNWINDING(
	" _backtrace: ended because callback returned %d", result);
	return result;
	}
	}
	}


	/// Find DWARF unwind info for an address 'pc' in some function.
	_LIBUNWIND_EXPORT const void _Unwind_Find_FDE(const void pc,
	struct dwarf_eh_bases *bases) {
	// This is slow, but works.
	// We create an unwind cursor then alter the IP to be pc
	unw_cursor_t cursor;
	unw_context_t uc;
	unw_proc_info_t info;
	__unw_getcontext(&uc);
	__unw_init_local(&cursor, &uc);
	__unw_set_reg(&cursor, UNW_REG_IP, (unw_word_t)(intptr_t)pc);
	__unw_get_proc_info(&cursor, &info);
	bases->tbase = (uintptr_t)info.extra;
	bases->dbase = 0; // dbase not used on Mac OS X
	bases->func = (uintptr_t)info.start_ip;
	_LIBUNWIND_TRACE_API("_Unwind_Find_FDE(pc=%p) => %p", pc,
	(void *)(intptr_t) info.unwind_info);
	return (void *)(intptr_t) info.unwind_info;
	}

	/// Returns the CFA (call frame area, or stack pointer at start of function)
	/// for the current context.
	_LIBUNWIND_EXPORT uintptr_t _Unwind_GetCFA(struct _Unwind_Context *context) {
	unw_cursor_t cursor = (unw_cursor_t )context;
	unw_word_t result;
	__unw_get_reg(cursor, UNW_REG_SP, &result);
	_LIBUNWIND_TRACE_API("_Unwind_GetCFA(context=%p) => 0x%" PRIxPTR,
	(void *)context, result);
	return (uintptr_t)result;
	}


	/// Called by personality handler during phase 2 to get instruction pointer.
	/// ipBefore is a boolean that says if IP is already adjusted to be the call
	/// site address. Normally IP is the return address.
	_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIPInfo(struct _Unwind_Context *context,
	int *ipBefore) {
	_LIBUNWIND_TRACE_API("_Unwind_GetIPInfo(context=%p)", (void *)context);
	int isSignalFrame = __unw_is_signal_frame((unw_cursor_t *)context);
	// Negative means some kind of error (probably UNW_ENOINFO), but we have no
	// good way to report that, and this maintains backward compatibility with the
	// implementation that hard-coded zero in every case, even signal frames.
	if (isSignalFrame <= 0)
	*ipBefore = 0;
	else
	*ipBefore = 1;
	return _Unwind_GetIP(context);
	}

	#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)

	/// Called by programs with dynamic code generators that want
	/// to register a dynamically generated FDE.
	/// This function has existed on Mac OS X since 10.4, but
	/// was broken until 10.6.
	_LIBUNWIND_EXPORT void __register_frame(const void *fde) {
	_LIBUNWIND_TRACE_API("__register_frame(%p)", fde);
	__unw_add_dynamic_fde((unw_word_t)(uintptr_t)fde);
	}


	/// Called by programs with dynamic code generators that want
	/// to unregister a dynamically generated FDE.
	/// This function has existed on Mac OS X since 10.4, but
	/// was broken until 10.6.
	_LIBUNWIND_EXPORT void __deregister_frame(const void *fde) {
	_LIBUNWIND_TRACE_API("__deregister_frame(%p)", fde);
	__unw_remove_dynamic_fde((unw_word_t)(uintptr_t)fde);
	}


	// The following register/deregister functions are gcc extensions.
	// They have existed on Mac OS X, but have never worked because Mac OS X
	// before 10.6 used keymgr to track known FDEs, but these functions
	// never got updated to use keymgr.
	// For now, we implement these as do-nothing functions to keep any existing
	// applications working. We also add the not in 10.6 symbol so that nwe
	// application won't be able to use them.

	#if defined(_LIBUNWIND_SUPPORT_FRAME_APIS)
	_LIBUNWIND_EXPORT void __register_frame_info_bases(const void fde, void ob,
	void tb, void db) {
	(void)fde;
	(void)ob;
	(void)tb;
	(void)db;
	_LIBUNWIND_TRACE_API("__register_frame_info_bases(%p,%p, %p, %p)",
	fde, ob, tb, db);
	// do nothing, this function never worked in Mac OS X
	}

	_LIBUNWIND_EXPORT void __register_frame_info(const void fde, void ob) {
	(void)fde;
	(void)ob;
	_LIBUNWIND_TRACE_API("__register_frame_info(%p, %p)", fde, ob);
	// do nothing, this function never worked in Mac OS X
	}

	_LIBUNWIND_EXPORT void __register_frame_info_table_bases(const void *fde,
	void ob, void tb,
	void *db) {
	(void)fde;
	(void)ob;
	(void)tb;
	(void)db;
	_LIBUNWIND_TRACE_API("__register_frame_info_table_bases"
	"(%p,%p, %p, %p)", fde, ob, tb, db);
	// do nothing, this function never worked in Mac OS X
	}

	_LIBUNWIND_EXPORT void __register_frame_info_table(const void fde, void ob) {
	(void)fde;
	(void)ob;
	_LIBUNWIND_TRACE_API("__register_frame_info_table(%p, %p)", fde, ob);
	// do nothing, this function never worked in Mac OS X
	}

	_LIBUNWIND_EXPORT void __register_frame_table(const void *fde) {
	(void)fde;
	_LIBUNWIND_TRACE_API("__register_frame_table(%p)", fde);
	// do nothing, this function never worked in Mac OS X
	}

	_LIBUNWIND_EXPORT void __deregister_frame_info(const void fde) {
	(void)fde;
	_LIBUNWIND_TRACE_API("__deregister_frame_info(%p)", fde);
	// do nothing, this function never worked in Mac OS X
	return NULL;
	}

	_LIBUNWIND_EXPORT void __deregister_frame_info_bases(const void fde) {
	(void)fde;
	_LIBUNWIND_TRACE_API("__deregister_frame_info_bases(%p)", fde);
	// do nothing, this function never worked in Mac OS X
	return NULL;
	}
	#endif // defined(_LIBUNWIND_SUPPORT_FRAME_APIS)

	#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)

	#endif // defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)