src/stacktrace.cc - external/github.com/gperftools/gperftools - Git at Google

 // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
 // Copyright (c) 2005, Google Inc.
 // Copyright (c) 2023, gperftools Contributors.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 // copyright notice, this list of conditions and the following disclaimer
 // in the documentation and/or other materials provided with the
 // distribution.
 //     * Neither the name of Google Inc. nor the names of its
 // contributors may be used to endorse or promote products derived from
 // this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // ---
 // Original Author: Sanjay Ghemawat.
 //
 // Most recent significant rework and extensions: Aliaksei
 // Kandratsenka (all bugs are mine).
 //
 // Produce stack trace.
 //
 // There few different ways we can try to get the stack trace:
 //
 // 1) Our hand-coded stack-unwinder.  This depends on a certain stack
 //    layout, which is used by various ABIs. It uses the frame
 //    pointer to do its work.
 //
 // 2) The libunwind library. It also doesn't call malloc (in most
 //    configurations). Note, there are at least 3 libunwind
 //    implementations currently available. "Original" libunwind,
 //    llvm's and Android's. Only original library has been tested so
 //    far.
 //
 // 3) The "libgcc" unwinder -- also the one used by the c++ exception
 //    code. It uses _Unwind_Backtrace facility of modern ABIs. Some
 //    implementations occasionally call into malloc (which we're able
 //    to handle). Some implementations also use some internal locks,
 //    so it is not entirely compatible with backtracing from signal
 //    handlers.
 //
 // 4) backtrace() unwinder (available in glibc and execinfo on some
 //    BSDs). It is typically, but not always implemented on top of
 //    "libgcc" unwinder. So we have it. We use this one on OSX.
 //
 // 5) On windows we use RtlCaptureStackBackTrace.
 //
 // Note: if you add a new implementation here, make sure it works
 // correctly when GetStackTrace() is called with max_depth == 0.
 // Some code may do that.

 #include <config.h>
 #include <stdlib.h> // for getenv
 #include <string.h> // for strcmp
 #include <stdio.h> // for fprintf
 #include "gperftools/stacktrace.h"
 #include "base/commandlineflags.h"
 #include "base/googleinit.h"
 #include "getenv_safe.h"


 // we're using plain struct and not class to avoid any possible issues
 // during initialization. Struct of pointers is easy to init at
 // link-time.
 struct GetStackImplementation {
   int (*GetStackFramesPtr)(void** result, int* sizes, int max_depth,
                            int skip_count);

   int (*GetStackFramesWithContextPtr)(void** result, int* sizes, int max_depth,
                                       int skip_count, const void *uc);

   int (*GetStackTracePtr)(void** result, int max_depth,
                           int skip_count);

   int (*GetStackTraceWithContextPtr)(void** result, int max_depth,
                                   int skip_count, const void *uc);

   const char *name;
 };

 #if HAVE_DECL_BACKTRACE
 #define STACKTRACE_INL_HEADER "stacktrace_generic-inl.h"
 #define GST_SUFFIX generic
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX
 #undef STACKTRACE_INL_HEADER
 #define HAVE_GST_generic
 #endif

 #ifdef HAVE_UNWIND_BACKTRACE
 #define STACKTRACE_INL_HEADER "stacktrace_libgcc-inl.h"
 #define GST_SUFFIX libgcc
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX
 #undef STACKTRACE_INL_HEADER
 #define HAVE_GST_libgcc
 #endif

 // libunwind uses __thread so we check for both libunwind.h and
 // __thread support
 #if defined(USE_LIBUNWIND) && defined(HAVE_TLS)
 #define STACKTRACE_INL_HEADER "stacktrace_libunwind-inl.h"
 #define GST_SUFFIX libunwind
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX
 #undef STACKTRACE_INL_HEADER
 #define HAVE_GST_libunwind
 #endif // USE_LIBUNWIND

 #if defined(__GNUC__) && (defined(__x86_64__) || defined(__i386__) || defined(__aarch64__) || defined(__riscv) || defined(__arm__))
 // NOTE: legacy 32-bit arm works fine with recent clangs, but is broken in gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92172
 #define STACKTRACE_INL_HEADER "stacktrace_generic_fp-inl.h"
 #define GST_SUFFIX generic_fp
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX
 #undef STACKTRACE_INL_HEADER
 #define HAVE_GST_generic_fp

 #undef TCMALLOC_UNSAFE_GENERIC_FP_STACKTRACE
 #define TCMALLOC_UNSAFE_GENERIC_FP_STACKTRACE 1

 #define STACKTRACE_INL_HEADER "stacktrace_generic_fp-inl.h"
 #define GST_SUFFIX generic_fp_unsafe
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX
 #undef STACKTRACE_INL_HEADER
 #define HAVE_GST_generic_fp_unsafe
 #endif

 #if defined(__ppc__) || defined(__PPC__)
 #if defined(__linux__)
 #define STACKTRACE_INL_HEADER "stacktrace_powerpc-linux-inl.h"
 #else
 #define STACKTRACE_INL_HEADER "stacktrace_powerpc-darwin-inl.h"
 #endif
 #define GST_SUFFIX ppc
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX
 #undef STACKTRACE_INL_HEADER
 #define HAVE_GST_ppc
 #endif

 #if defined(__arm__)
 #define STACKTRACE_INL_HEADER "stacktrace_arm-inl.h"
 #define GST_SUFFIX arm
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX
 #undef STACKTRACE_INL_HEADER
 #define HAVE_GST_arm
 #endif

 #ifdef TCMALLOC_ENABLE_INSTRUMENT_STACKTRACE
 #define STACKTRACE_INL_HEADER "stacktrace_instrument-inl.h"
 #define GST_SUFFIX instrument
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX
 #undef STACKTRACE_INL_HEADER
 #define HAVE_GST_instrument
 #endif

 // The Windows case -- probably cygwin and mingw will use one of the
 // x86-includes above, but if not, we can fall back to windows intrinsics.
 #if defined(_WIN32) || defined(__CYGWIN__) || defined(__CYGWIN32__) || defined(__MINGW32__)
 #define STACKTRACE_INL_HEADER "stacktrace_win32-inl.h"
 #define GST_SUFFIX win32
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX
 #undef STACKTRACE_INL_HEADER
 #define HAVE_GST_win32
 #endif

 #if __cplusplus >= 202302L
 # ifndef HAS_SOME_STACKTRACE_IMPL
 #  warning "Warning: no stacktrace capturing implementation for your OS"
 # endif
 #endif

 #if (__x86_64__ || __i386__) && FORCED_FRAME_POINTERS
 // x86-es (even i386 this days) default to no frame pointers. But
 // historically we defaulted to frame pointer unwinder whenever
 // --enable-frame-pointers is given. So we keep this behavior.
 #define PREFER_FP_UNWINDER 1
 #elif TCMALLOC_DONT_PREFER_LIBUNWIND && !defined(PREFER_LIBGCC_UNWINDER)
 #define PREFER_FP_UNWINDER 1
 #else
 #define PREFER_FP_UNWINDER 0
 #endif

 #if defined(PREFER_LIBGCC_UNWINDER) && !defined(HAVE_GST_libgcc)
 #error user asked for libgcc unwinder to be default but it is not available
 #endif

 static int null_GetStackFrames(void** result, int* sizes, int max_depth,
                                int skip_count) {
   return 0;
 }

 static int null_GetStackFramesWithContext(void** result, int* sizes, int max_depth,
                                           int skip_count, const void *uc) {
   return 0;
 }

 static int null_GetStackTrace(void** result, int max_depth,
                               int skip_count) {
   return 0;
 }

 static int null_GetStackTraceWithContext(void** result, int max_depth,
                                          int skip_count, const void *uc) {
   return 0;
 }

 static GetStackImplementation impl__null = {
   null_GetStackFrames,
   null_GetStackFramesWithContext,
   null_GetStackTrace,
   null_GetStackTraceWithContext,
   "null"
 };

 static GetStackImplementation *all_impls[] = {
 #ifdef HAVE_GST_instrument
   &impl__instrument,
 #endif
 #ifdef HAVE_GST_win32
   &impl__win32,
 #endif
 #ifdef HAVE_GST_ppc
   &impl__ppc,
 #endif
 #if defined(HAVE_GST_generic_fp) && PREFER_FP_UNWINDER
   &impl__generic_fp,
   &impl__generic_fp_unsafe,
 #endif
 #if defined(HAVE_GST_libgcc) && defined(PREFER_LIBGCC_UNWINDER)
   &impl__libgcc,
 #endif
 #ifdef HAVE_GST_libunwind
   &impl__libunwind,
 #endif
 #if defined(HAVE_GST_libgcc) && !defined(PREFER_LIBGCC_UNWINDER)
   &impl__libgcc,
 #endif
 #ifdef HAVE_GST_generic
   &impl__generic,
 #endif
 #if defined(HAVE_GST_generic_fp) && !PREFER_FP_UNWINDER
   &impl__generic_fp,
   &impl__generic_fp_unsafe,
 #endif
 #ifdef HAVE_GST_arm
   &impl__arm,
 #endif
   &impl__null
 };

 static bool get_stack_impl_inited;
 static GetStackImplementation *get_stack_impl;

 #if 0
 // This is for the benefit of code analysis tools that may have
 // trouble with the computed #include above.
 # include "stacktrace_libunwind-inl.h"
 # include "stacktrace_generic-inl.h"
 # include "stacktrace_generic_fp-inl.h"
 # include "stacktrace_powerpc-linux-inl.h"
 # include "stacktrace_win32-inl.h"
 # include "stacktrace_arm-inl.h"
 # include "stacktrace_instrument-inl.h"
 #endif

 static void init_default_stack_impl_inner(void);

 namespace tcmalloc {
   bool EnterStacktraceScope(void);
   void LeaveStacktraceScope(void);
 }

 namespace {
 using tcmalloc::EnterStacktraceScope;
 using tcmalloc::LeaveStacktraceScope;

 class StacktraceScope {
   bool stacktrace_allowed;
 public:
   StacktraceScope() {
     stacktrace_allowed = true;
     stacktrace_allowed = EnterStacktraceScope();
   }
   bool IsStacktraceAllowed() {
     return stacktrace_allowed;
   }
   // NOTE: noinline here ensures that we don't tail-call GetStackXXX
   // calls below. Which is crucial due to us having to pay attention
   // to skip_count argument.
   ATTRIBUTE_NOINLINE ~StacktraceScope() {
     if (stacktrace_allowed) {
       LeaveStacktraceScope();
     }
   }
 };

 }  // namespace

 ATTRIBUTE_NOINLINE
 PERFTOOLS_DLL_DECL int GetStackFrames(void** result, int* sizes, int max_depth,
                                       int skip_count) {
   StacktraceScope scope;
   if (!scope.IsStacktraceAllowed()) {
     return 0;
   }
   init_default_stack_impl_inner();
   return get_stack_impl->GetStackFramesPtr(result, sizes,
                                            max_depth, skip_count);
 }

 ATTRIBUTE_NOINLINE
 PERFTOOLS_DLL_DECL int GetStackFramesWithContext(void** result, int* sizes, int max_depth,
                                                  int skip_count, const void *uc) {
   StacktraceScope scope;
   if (!scope.IsStacktraceAllowed()) {
     return 0;
   }
   init_default_stack_impl_inner();
   return get_stack_impl->GetStackFramesWithContextPtr(result, sizes, max_depth,
                                                       skip_count, uc);
 }

 ATTRIBUTE_NOINLINE
 PERFTOOLS_DLL_DECL int GetStackTrace(void** result, int max_depth,
                                      int skip_count) {
   StacktraceScope scope;
   if (!scope.IsStacktraceAllowed()) {
     return 0;
   }
   init_default_stack_impl_inner();
   return get_stack_impl->GetStackTracePtr(result, max_depth, skip_count);
 }

 ATTRIBUTE_NOINLINE
 PERFTOOLS_DLL_DECL int GetStackTraceWithContext(void** result, int max_depth,
                                                 int skip_count, const void *uc) {
   StacktraceScope scope;
   if (!scope.IsStacktraceAllowed()) {
     return 0;
   }
   init_default_stack_impl_inner();
   return get_stack_impl->GetStackTraceWithContextPtr(result, max_depth,
                                                      skip_count, uc);
 }

 #if STACKTRACE_IS_TESTED
 static void init_default_stack_impl_inner() {
 }

 extern "C" {
 const char* TEST_bump_stacktrace_implementation(const char* suggestion) {
   static int selection;
   constexpr int n = sizeof(all_impls)/sizeof(all_impls[0]);

   if (!get_stack_impl_inited) {
     fprintf(stderr, "Supported stacktrace methods:\n");
     for (int i = 0; i < n; i++) {
       fprintf(stderr, "* %s\n", all_impls[i]->name);
     }
     fprintf(stderr, "\n\n");
     get_stack_impl_inited = true;
   }

   do {
     if (selection == n) {
       return nullptr;
     }
     get_stack_impl = all_impls[selection++];

     if (suggestion && strcmp(suggestion, get_stack_impl->name) != 0) {
       continue;
     }
     if (get_stack_impl == &impl__null) {
       // skip null implementation
       continue;
     }
     break;
   } while (true);

   return get_stack_impl->name;
 }
 }

 #else  // !STACKTRACE_IS_TESTED

 ATTRIBUTE_NOINLINE
 static void maybe_convert_libunwind_to_generic_fp() {
 #if defined(HAVE_GST_libunwind) && defined(HAVE_GST_generic_fp)
   if (get_stack_impl != &impl__libunwind) {
     return;
   }

   bool want_to_replace = false;

   // Sometime recently, aarch64 had completely borked libunwind, so
   // lets test this case and fall back to frame pointers (which is
   // nearly but not quite perfect). So lets check this case.
   void* stack[4];
   int rv = get_stack_impl->GetStackTracePtr(stack, 4, 0);
   want_to_replace = (rv <= 2);

   if (want_to_replace) {
     get_stack_impl = &impl__generic_fp;
   }
 #endif  // have libunwind and generic_fp
 }

 static void init_default_stack_impl_inner(void) {
   if (get_stack_impl_inited) {
     return;
   }
   get_stack_impl = all_impls[0];
   get_stack_impl_inited = true;
   const char *val = TCMallocGetenvSafe("TCMALLOC_STACKTRACE_METHOD");
   if (!val || !*val) {
     // If no explicit implementation is requested, consider changing
     // libunwind->generic_fp in some cases.
     maybe_convert_libunwind_to_generic_fp();
     return;
   }
   for (int i = 0; i < sizeof(all_impls) / sizeof(all_impls[0]); i++) {
     GetStackImplementation *c = all_impls[i];
     if (strcmp(c->name, val) == 0) {
       get_stack_impl = c;
       return;
     }
   }
   fprintf(stderr, "Unknown or unsupported stacktrace method requested: %s. Ignoring it\n", val);
 }

 ATTRIBUTE_NOINLINE
 static void init_default_stack_impl(void) {
   init_default_stack_impl_inner();
   if (EnvToBool("TCMALLOC_STACKTRACE_METHOD_VERBOSE", false)) {
     fprintf(stderr, "Chosen stacktrace method is %s\nSupported methods:\n", get_stack_impl->name);
     for (int i = 0; i < sizeof(all_impls) / sizeof(all_impls[0]); i++) {
       GetStackImplementation *c = all_impls[i];
       fprintf(stderr, "* %s\n", c->name);
     }
     fputs("\nUse TCMALLOC_STACKTRACE_METHOD environment variable to override\n", stderr);
   }
 }

 REGISTER_MODULE_INITIALIZER(stacktrace_init_default_stack_impl, init_default_stack_impl());

 #endif  // !STACKTRACE_IS_TESTED
	// -- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil --
	// Copyright (c) 2005, Google Inc.
	// Copyright (c) 2023, gperftools Contributors.
	// All rights reserved.
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are
	// met:
	//
	// * Redistributions of source code must retain the above copyright
	// notice, this list of conditions and the following disclaimer.
	// * Redistributions in binary form must reproduce the above
	// copyright notice, this list of conditions and the following disclaimer
	// in the documentation and/or other materials provided with the
	// distribution.
	// * Neither the name of Google Inc. nor the names of its
	// contributors may be used to endorse or promote products derived from
	// this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	// ---
	// Original Author: Sanjay Ghemawat.
	//
	// Most recent significant rework and extensions: Aliaksei
	// Kandratsenka (all bugs are mine).
	//
	// Produce stack trace.
	//
	// There few different ways we can try to get the stack trace:
	//
	// 1) Our hand-coded stack-unwinder. This depends on a certain stack
	// layout, which is used by various ABIs. It uses the frame
	// pointer to do its work.
	//
	// 2) The libunwind library. It also doesn't call malloc (in most
	// configurations). Note, there are at least 3 libunwind
	// implementations currently available. "Original" libunwind,
	// llvm's and Android's. Only original library has been tested so
	// far.
	//
	// 3) The "libgcc" unwinder -- also the one used by the c++ exception
	// code. It uses _Unwind_Backtrace facility of modern ABIs. Some
	// implementations occasionally call into malloc (which we're able
	// to handle). Some implementations also use some internal locks,
	// so it is not entirely compatible with backtracing from signal
	// handlers.
	//
	// 4) backtrace() unwinder (available in glibc and execinfo on some
	// BSDs). It is typically, but not always implemented on top of
	// "libgcc" unwinder. So we have it. We use this one on OSX.
	//
	// 5) On windows we use RtlCaptureStackBackTrace.
	//
	// Note: if you add a new implementation here, make sure it works
	// correctly when GetStackTrace() is called with max_depth == 0.
	// Some code may do that.

	#include <config.h>
	#include <stdlib.h> // for getenv
	#include <string.h> // for strcmp
	#include <stdio.h> // for fprintf
	#include "gperftools/stacktrace.h"
	#include "base/commandlineflags.h"
	#include "base/googleinit.h"
	#include "getenv_safe.h"


	// we're using plain struct and not class to avoid any possible issues
	// during initialization. Struct of pointers is easy to init at
	// link-time.
	struct GetStackImplementation {
	int (GetStackFramesPtr)(void* result, int* sizes, int max_depth,
	int skip_count);

	int (GetStackFramesWithContextPtr)(void* result, int* sizes, int max_depth,
	int skip_count, const void *uc);

	int (GetStackTracePtr)(void* result, int max_depth,
	int skip_count);

	int (GetStackTraceWithContextPtr)(void* result, int max_depth,
	int skip_count, const void *uc);

	const char *name;
	};

	#if HAVE_DECL_BACKTRACE
	#define STACKTRACE_INL_HEADER "stacktrace_generic-inl.h"
	#define GST_SUFFIX generic
	#include "stacktrace_impl_setup-inl.h"
	#undef GST_SUFFIX
	#undef STACKTRACE_INL_HEADER
	#define HAVE_GST_generic
	#endif

	#ifdef HAVE_UNWIND_BACKTRACE
	#define STACKTRACE_INL_HEADER "stacktrace_libgcc-inl.h"
	#define GST_SUFFIX libgcc
	#include "stacktrace_impl_setup-inl.h"
	#undef GST_SUFFIX
	#undef STACKTRACE_INL_HEADER
	#define HAVE_GST_libgcc
	#endif

	// libunwind uses __thread so we check for both libunwind.h and
	// __thread support
	#if defined(USE_LIBUNWIND) && defined(HAVE_TLS)
	#define STACKTRACE_INL_HEADER "stacktrace_libunwind-inl.h"
	#define GST_SUFFIX libunwind
	#include "stacktrace_impl_setup-inl.h"
	#undef GST_SUFFIX
	#undef STACKTRACE_INL_HEADER
	#define HAVE_GST_libunwind
	#endif // USE_LIBUNWIND

	#if defined(__GNUC__) && (defined(__x86_64__) \|\| defined(__i386__) \|\| defined(__aarch64__) \|\| defined(__riscv) \|\| defined(__arm__))
	// NOTE: legacy 32-bit arm works fine with recent clangs, but is broken in gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92172
	#define STACKTRACE_INL_HEADER "stacktrace_generic_fp-inl.h"
	#define GST_SUFFIX generic_fp
	#include "stacktrace_impl_setup-inl.h"
	#undef GST_SUFFIX
	#undef STACKTRACE_INL_HEADER
	#define HAVE_GST_generic_fp

	#undef TCMALLOC_UNSAFE_GENERIC_FP_STACKTRACE
	#define TCMALLOC_UNSAFE_GENERIC_FP_STACKTRACE 1

	#define STACKTRACE_INL_HEADER "stacktrace_generic_fp-inl.h"
	#define GST_SUFFIX generic_fp_unsafe
	#include "stacktrace_impl_setup-inl.h"
	#undef GST_SUFFIX
	#undef STACKTRACE_INL_HEADER
	#define HAVE_GST_generic_fp_unsafe
	#endif

	#if defined(__ppc__) \|\| defined(__PPC__)
	#if defined(__linux__)
	#define STACKTRACE_INL_HEADER "stacktrace_powerpc-linux-inl.h"
	#else
	#define STACKTRACE_INL_HEADER "stacktrace_powerpc-darwin-inl.h"
	#endif
	#define GST_SUFFIX ppc
	#include "stacktrace_impl_setup-inl.h"
	#undef GST_SUFFIX
	#undef STACKTRACE_INL_HEADER
	#define HAVE_GST_ppc
	#endif

	#if defined(__arm__)
	#define STACKTRACE_INL_HEADER "stacktrace_arm-inl.h"
	#define GST_SUFFIX arm
	#include "stacktrace_impl_setup-inl.h"
	#undef GST_SUFFIX
	#undef STACKTRACE_INL_HEADER
	#define HAVE_GST_arm
	#endif

	#ifdef TCMALLOC_ENABLE_INSTRUMENT_STACKTRACE
	#define STACKTRACE_INL_HEADER "stacktrace_instrument-inl.h"
	#define GST_SUFFIX instrument
	#include "stacktrace_impl_setup-inl.h"
	#undef GST_SUFFIX
	#undef STACKTRACE_INL_HEADER
	#define HAVE_GST_instrument
	#endif

	// The Windows case -- probably cygwin and mingw will use one of the
	// x86-includes above, but if not, we can fall back to windows intrinsics.
	#if defined(_WIN32) \|\| defined(__CYGWIN__) \|\| defined(__CYGWIN32__) \|\| defined(__MINGW32__)
	#define STACKTRACE_INL_HEADER "stacktrace_win32-inl.h"
	#define GST_SUFFIX win32
	#include "stacktrace_impl_setup-inl.h"
	#undef GST_SUFFIX
	#undef STACKTRACE_INL_HEADER
	#define HAVE_GST_win32
	#endif

	#if __cplusplus >= 202302L
	# ifndef HAS_SOME_STACKTRACE_IMPL
	# warning "Warning: no stacktrace capturing implementation for your OS"
	# endif
	#endif

	#if (__x86_64__ \|\| __i386__) && FORCED_FRAME_POINTERS
	// x86-es (even i386 this days) default to no frame pointers. But
	// historically we defaulted to frame pointer unwinder whenever
	// --enable-frame-pointers is given. So we keep this behavior.
	#define PREFER_FP_UNWINDER 1
	#elif TCMALLOC_DONT_PREFER_LIBUNWIND && !defined(PREFER_LIBGCC_UNWINDER)
	#define PREFER_FP_UNWINDER 1
	#else
	#define PREFER_FP_UNWINDER 0
	#endif

	#if defined(PREFER_LIBGCC_UNWINDER) && !defined(HAVE_GST_libgcc)
	#error user asked for libgcc unwinder to be default but it is not available
	#endif

	static int null_GetStackFrames(void** result, int* sizes, int max_depth,
	int skip_count) {
	return 0;
	}

	static int null_GetStackFramesWithContext(void** result, int* sizes, int max_depth,
	int skip_count, const void *uc) {
	return 0;
	}

	static int null_GetStackTrace(void** result, int max_depth,
	int skip_count) {
	return 0;
	}

	static int null_GetStackTraceWithContext(void** result, int max_depth,
	int skip_count, const void *uc) {
	return 0;
	}

	static GetStackImplementation impl__null = {
	null_GetStackFrames,
	null_GetStackFramesWithContext,
	null_GetStackTrace,
	null_GetStackTraceWithContext,
	"null"
	};

	static GetStackImplementation *all_impls[] = {
	#ifdef HAVE_GST_instrument
	&impl__instrument,
	#endif
	#ifdef HAVE_GST_win32
	&impl__win32,
	#endif
	#ifdef HAVE_GST_ppc
	&impl__ppc,
	#endif
	#if defined(HAVE_GST_generic_fp) && PREFER_FP_UNWINDER
	&impl__generic_fp,
	&impl__generic_fp_unsafe,
	#endif
	#if defined(HAVE_GST_libgcc) && defined(PREFER_LIBGCC_UNWINDER)
	&impl__libgcc,
	#endif
	#ifdef HAVE_GST_libunwind
	&impl__libunwind,
	#endif
	#if defined(HAVE_GST_libgcc) && !defined(PREFER_LIBGCC_UNWINDER)
	&impl__libgcc,
	#endif
	#ifdef HAVE_GST_generic
	&impl__generic,
	#endif
	#if defined(HAVE_GST_generic_fp) && !PREFER_FP_UNWINDER
	&impl__generic_fp,
	&impl__generic_fp_unsafe,
	#endif
	#ifdef HAVE_GST_arm
	&impl__arm,
	#endif
	&impl__null
	};

	static bool get_stack_impl_inited;
	static GetStackImplementation *get_stack_impl;

	#if 0
	// This is for the benefit of code analysis tools that may have
	// trouble with the computed #include above.
	# include "stacktrace_libunwind-inl.h"
	# include "stacktrace_generic-inl.h"
	# include "stacktrace_generic_fp-inl.h"
	# include "stacktrace_powerpc-linux-inl.h"
	# include "stacktrace_win32-inl.h"
	# include "stacktrace_arm-inl.h"
	# include "stacktrace_instrument-inl.h"
	#endif

	static void init_default_stack_impl_inner(void);

	namespace tcmalloc {
	bool EnterStacktraceScope(void);
	void LeaveStacktraceScope(void);
	}

	namespace {
	using tcmalloc::EnterStacktraceScope;
	using tcmalloc::LeaveStacktraceScope;

	class StacktraceScope {
	bool stacktrace_allowed;
	public:
	StacktraceScope() {
	stacktrace_allowed = true;
	stacktrace_allowed = EnterStacktraceScope();
	}
	bool IsStacktraceAllowed() {
	return stacktrace_allowed;
	}
	// NOTE: noinline here ensures that we don't tail-call GetStackXXX
	// calls below. Which is crucial due to us having to pay attention
	// to skip_count argument.
	ATTRIBUTE_NOINLINE ~StacktraceScope() {
	if (stacktrace_allowed) {
	LeaveStacktraceScope();
	}
	}
	};

	} // namespace

	ATTRIBUTE_NOINLINE
	PERFTOOLS_DLL_DECL int GetStackFrames(void** result, int* sizes, int max_depth,
	int skip_count) {
	StacktraceScope scope;
	if (!scope.IsStacktraceAllowed()) {
	return 0;
	}
	init_default_stack_impl_inner();
	return get_stack_impl->GetStackFramesPtr(result, sizes,
	max_depth, skip_count);
	}

	ATTRIBUTE_NOINLINE
	PERFTOOLS_DLL_DECL int GetStackFramesWithContext(void** result, int* sizes, int max_depth,
	int skip_count, const void *uc) {
	StacktraceScope scope;
	if (!scope.IsStacktraceAllowed()) {
	return 0;
	}
	init_default_stack_impl_inner();
	return get_stack_impl->GetStackFramesWithContextPtr(result, sizes, max_depth,
	skip_count, uc);
	}

	ATTRIBUTE_NOINLINE
	PERFTOOLS_DLL_DECL int GetStackTrace(void** result, int max_depth,
	int skip_count) {
	StacktraceScope scope;
	if (!scope.IsStacktraceAllowed()) {
	return 0;
	}
	init_default_stack_impl_inner();
	return get_stack_impl->GetStackTracePtr(result, max_depth, skip_count);
	}

	ATTRIBUTE_NOINLINE
	PERFTOOLS_DLL_DECL int GetStackTraceWithContext(void** result, int max_depth,
	int skip_count, const void *uc) {
	StacktraceScope scope;
	if (!scope.IsStacktraceAllowed()) {
	return 0;
	}
	init_default_stack_impl_inner();
	return get_stack_impl->GetStackTraceWithContextPtr(result, max_depth,
	skip_count, uc);
	}

	#if STACKTRACE_IS_TESTED
	static void init_default_stack_impl_inner() {
	}

	extern "C" {
	const char* TEST_bump_stacktrace_implementation(const char* suggestion) {
	static int selection;
	constexpr int n = sizeof(all_impls)/sizeof(all_impls[0]);

	if (!get_stack_impl_inited) {
	fprintf(stderr, "Supported stacktrace methods:\n");
	for (int i = 0; i < n; i++) {
	fprintf(stderr, "* %s\n", all_impls[i]->name);
	}
	fprintf(stderr, "\n\n");
	get_stack_impl_inited = true;
	}

	do {
	if (selection == n) {
	return nullptr;
	}
	get_stack_impl = all_impls[selection++];

	if (suggestion && strcmp(suggestion, get_stack_impl->name) != 0) {
	continue;
	}
	if (get_stack_impl == &impl__null) {
	// skip null implementation
	continue;
	}
	break;
	} while (true);

	return get_stack_impl->name;
	}
	}

	#else // !STACKTRACE_IS_TESTED

	ATTRIBUTE_NOINLINE
	static void maybe_convert_libunwind_to_generic_fp() {
	#if defined(HAVE_GST_libunwind) && defined(HAVE_GST_generic_fp)
	if (get_stack_impl != &impl__libunwind) {
	return;
	}

	bool want_to_replace = false;

	// Sometime recently, aarch64 had completely borked libunwind, so
	// lets test this case and fall back to frame pointers (which is
	// nearly but not quite perfect). So lets check this case.
	void* stack[4];
	int rv = get_stack_impl->GetStackTracePtr(stack, 4, 0);
	want_to_replace = (rv <= 2);

	if (want_to_replace) {
	get_stack_impl = &impl__generic_fp;
	}
	#endif // have libunwind and generic_fp
	}

	static void init_default_stack_impl_inner(void) {
	if (get_stack_impl_inited) {
	return;
	}
	get_stack_impl = all_impls[0];
	get_stack_impl_inited = true;
	const char *val = TCMallocGetenvSafe("TCMALLOC_STACKTRACE_METHOD");
	if (!val \|\| !*val) {
	// If no explicit implementation is requested, consider changing
	// libunwind->generic_fp in some cases.
	maybe_convert_libunwind_to_generic_fp();
	return;
	}
	for (int i = 0; i < sizeof(all_impls) / sizeof(all_impls[0]); i++) {
	GetStackImplementation *c = all_impls[i];
	if (strcmp(c->name, val) == 0) {
	get_stack_impl = c;
	return;
	}
	}
	fprintf(stderr, "Unknown or unsupported stacktrace method requested: %s. Ignoring it\n", val);
	}

	ATTRIBUTE_NOINLINE
	static void init_default_stack_impl(void) {
	init_default_stack_impl_inner();
	if (EnvToBool("TCMALLOC_STACKTRACE_METHOD_VERBOSE", false)) {
	fprintf(stderr, "Chosen stacktrace method is %s\nSupported methods:\n", get_stack_impl->name);
	for (int i = 0; i < sizeof(all_impls) / sizeof(all_impls[0]); i++) {
	GetStackImplementation *c = all_impls[i];
	fprintf(stderr, "* %s\n", c->name);
	}
	fputs("\nUse TCMALLOC_STACKTRACE_METHOD environment variable to override\n", stderr);
	}
	}

	REGISTER_MODULE_INITIALIZER(stacktrace_init_default_stack_impl, init_default_stack_impl());

	#endif // !STACKTRACE_IS_TESTED