Add libbacktrace

1 files changed, 1418 insertions, 0 deletions

diff --git a/3rdparty/libbacktrace/macho.c b/3rdparty/libbacktrace/macho.c
new file mode 100644
index 000000000..b43ea22fe
--- /dev/null
+++ b/3rdparty/libbacktrace/macho.c
@@ -0,0 +1,1418 @@
+/* macho.c -- Get debug data from an Mach-O file for backtraces.
+   Copyright (C) 2012-2016 Free Software Foundation, Inc.
+   Written by John Colanduoni.
+
+   Pending upstream pull request:
+   https://github.com/ianlancetaylor/libbacktrace/pull/2
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    (1) Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+
+    (2) 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.
+
+    (3) The name of the author may not be used to
+    endorse or promote products derived from this software without
+    specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.  */
+
+#include "config.h"
+
+/* We can't use autotools to detect the pointer width of our program because
+   we may be building a fat Mach-O file containing both 32-bit and 64-bit
+   variants. However Mach-O runs a limited set of platforms so detection
+   via preprocessor is not difficult.  */
+
+#if defined(__MACH__)
+#if defined(__LP64__)
+#define BACKTRACE_BITS 64
+#else
+#define BACKTRACE_BITS 32
+#endif
+#else
+#error Attempting to build Mach-O support on incorrect platform
+#endif
+
+#if defined(__x86_64__)
+#define NATIVE_CPU_TYPE CPU_TYPE_X86_64
+#elif defined(__i386__)
+#define NATIVE_CPU_TYPE CPU_TYPE_X86
+#elif defined(__aarch64__)
+#define NATIVE_CPU_TYPE CPU_TYPE_ARM64
+#elif defined(__arm__)
+#define NATIVE_CPU_TYPE CPU_TYPE_ARM
+#else
+#error Could not detect native Mach-O cpu_type_t
+#endif
+
+#include <sys/types.h>
+#include <sys/syslimits.h>
+#include <string.h>
+#include <mach-o/loader.h>
+#include <mach-o/nlist.h>
+#include <mach-o/fat.h>
+#include <mach-o/dyld.h>
+#include <uuid/uuid.h>
+#include <dirent.h>
+#include <stdlib.h>
+
+#include "backtrace.h"
+#include "internal.h"
+
+struct macho_commands_view
+{
+    struct backtrace_view view;
+    uint32_t commands_count;
+    uint32_t commands_total_size;
+    int bytes_swapped;
+    size_t base_offset;
+};
+
+enum debug_section
+{
+    DEBUG_INFO,
+    DEBUG_LINE,
+    DEBUG_ABBREV,
+    DEBUG_RANGES,
+    DEBUG_STR,
+    DEBUG_MAX
+};
+
+static const char *const debug_section_names[DEBUG_MAX] =
+    {
+        "__debug_info",
+        "__debug_line",
+        "__debug_abbrev",
+        "__debug_ranges",
+        "__debug_str"
+    };
+
+struct found_dwarf_section
+{
+    uint32_t file_offset;
+    uintptr_t file_size;
+    const unsigned char *data;
+};
+
+/* Mach-O symbols don't have a length. As a result we have to infer it
+   by sorting the symbol addresses for each image and recording the
+   memory range attributed to each image.  */
+struct macho_symbol
+{
+    uintptr_t addr;
+    size_t size;
+    const char *name;
+};
+
+struct macho_syminfo_data
+{
+    struct macho_syminfo_data *next;
+    struct macho_symbol *symbols;
+    size_t symbol_count;
+    uintptr_t min_addr;
+    uintptr_t max_addr;
+};
+
+uint16_t
+macho_file_to_host_u16 (int file_bytes_swapped, uint16_t input)
+{
+  if (file_bytes_swapped)
+    return (input >> 8) | (input << 8);
+  else
+    return input;
+}
+
+uint32_t
+macho_file_to_host_u32 (int file_bytes_swapped, uint32_t input)
+{
+  if (file_bytes_swapped)
+    {
+      return ((input >> 24) & 0x000000FF)
+             | ((input >> 8) & 0x0000FF00)
+             | ((input << 8) & 0x00FF0000)
+             | ((input << 24) & 0xFF000000);
+    }
+  else
+    {
+      return input;
+    }
+}
+
+uint64_t
+macho_file_to_host_u64 (int file_bytes_swapped, uint64_t input)
+{
+  if (file_bytes_swapped)
+    {
+      return macho_file_to_host_u32 (file_bytes_swapped,
+                                     (uint32_t) (input >> 32))
+             | (((uint64_t) macho_file_to_host_u32 (file_bytes_swapped,
+                                                    (uint32_t) input)) << 32);
+    }
+  else
+    {
+      return input;
+    }
+}
+
+#if BACKTRACE_BITS == 64
+#define macho_file_to_host_usize macho_file_to_host_u64
+typedef struct mach_header_64 mach_header_native_t;
+#define LC_SEGMENT_NATIVE LC_SEGMENT_64
+typedef struct segment_command_64 segment_command_native_t;
+typedef struct nlist_64 nlist_native_t;
+typedef struct section_64 section_native_t;
+#else /* BACKTRACE_BITS == 32 */
+#define macho_file_to_host_usize macho_file_to_host_u32
+typedef struct mach_header mach_header_native_t;
+#define LC_SEGMENT_NATIVE LC_SEGMENT
+typedef struct segment_command segment_command_native_t;
+typedef struct nlist nlist_native_t;
+typedef struct section section_native_t;
+#endif
+
+// Gets a view into a Mach-O image, taking any slice offset into account
+int
+macho_get_view (struct backtrace_state *state, int descriptor,
+                off_t offset, size_t size,
+                backtrace_error_callback error_callback,
+                void *data, struct macho_commands_view *commands_view,
+                struct backtrace_view *view)
+{
+  return backtrace_get_view (state, descriptor,
+                             commands_view->base_offset + offset, size,
+                             error_callback, data, view);
+}
+
+int
+macho_get_commands (struct backtrace_state *state, int descriptor,
+                    backtrace_error_callback error_callback,
+                    void *data, struct macho_commands_view *commands_view,
+                    int *incompatible)
+{
+  int ret = 0;
+  int is_fat = 0;
+  struct backtrace_view file_header_view;
+  int file_header_view_valid = 0;
+  struct backtrace_view fat_archs_view;
+  int fat_archs_view_valid = 0;
+  const mach_header_native_t *file_header;
+  uint64_t commands_offset;
+
+  *incompatible = 0;
+
+  if (!backtrace_get_view (state, descriptor, 0, sizeof (mach_header_native_t),
+                           error_callback, data, &file_header_view))
+    goto end;
+  file_header_view_valid = 1;
+
+  switch (*(uint32_t *) file_header_view.data)
+    {
+      case MH_MAGIC:
+        if (BACKTRACE_BITS == 32)
+          commands_view->bytes_swapped = 0;
+        else
+          {
+            *incompatible = 1;
+            goto end;
+          }
+      break;
+      case MH_CIGAM:
+        if (BACKTRACE_BITS == 32)
+          commands_view->bytes_swapped = 1;
+        else
+          {
+            *incompatible = 1;
+            goto end;
+          }
+      break;
+      case MH_MAGIC_64:
+        if (BACKTRACE_BITS == 64)
+          commands_view->bytes_swapped = 0;
+        else
+          {
+            *incompatible = 1;
+            goto end;
+          }
+      break;
+      case MH_CIGAM_64:
+        if (BACKTRACE_BITS == 64)
+          commands_view->bytes_swapped = 1;
+        else
+          {
+            *incompatible = 1;
+            goto end;
+          }
+      break;
+      case FAT_MAGIC:
+        is_fat = 1;
+        commands_view->bytes_swapped = 0;
+      break;
+      case FAT_CIGAM:
+        is_fat = 1;
+        commands_view->bytes_swapped = 1;
+      break;
+      default:
+        goto end;
+    }
+
+  if (is_fat)
+    {
+      uint32_t native_slice_offset;
+      size_t archs_total_size;
+      uint32_t arch_count;
+      const struct fat_header *fat_header;
+      const struct fat_arch *archs;
+      uint32_t i;
+
+      fat_header = file_header_view.data;
+      arch_count =
+          macho_file_to_host_u32 (commands_view->bytes_swapped,
+                                  fat_header->nfat_arch);
+
+      archs_total_size = arch_count * sizeof (struct fat_arch);
+
+      if (!backtrace_get_view (state, descriptor, sizeof (struct fat_header),
+                               archs_total_size, error_callback,
+                               data, &fat_archs_view))
+        goto end;
+      fat_archs_view_valid = 1;
+
+      native_slice_offset = 0;
+      archs = fat_archs_view.data;
+      for (i = 0; i < arch_count; i++)
+        {
+          const struct fat_arch *raw_arch = archs + i;
+          int cpu_type =
+              (int) macho_file_to_host_u32 (commands_view->bytes_swapped,
+                                            (uint32_t) raw_arch->cputype);
+
+          if (cpu_type == NATIVE_CPU_TYPE)
+            {
+              native_slice_offset =
+                  macho_file_to_host_u32 (commands_view->bytes_swapped,
+                                          raw_arch->offset);
+
+              break;
+            }
+        }
+
+      if (native_slice_offset == 0)
+        {
+          *incompatible = 1;
+          goto end;
+        }
+
+      backtrace_release_view (state, &file_header_view, error_callback, data);
+      file_header_view_valid = 0;
+      if (!backtrace_get_view (state, descriptor, native_slice_offset,
+                               sizeof (mach_header_native_t), error_callback,
+                               data, &file_header_view))
+        goto end;
+      file_header_view_valid = 1;
+
+      // The endianess of the slice may be different than the fat image
+      switch (*(uint32_t *) file_header_view.data)
+        {
+          case MH_MAGIC:
+            if (BACKTRACE_BITS == 32)
+              commands_view->bytes_swapped = 0;
+            else
+              goto end;
+          break;
+          case MH_CIGAM:
+            if (BACKTRACE_BITS == 32)
+              commands_view->bytes_swapped = 1;
+            else
+              goto end;
+          break;
+          case MH_MAGIC_64:
+            if (BACKTRACE_BITS == 64)
+              commands_view->bytes_swapped = 0;
+            else
+              goto end;
+          break;
+          case MH_CIGAM_64:
+            if (BACKTRACE_BITS == 64)
+              commands_view->bytes_swapped = 1;
+            else
+              goto end;
+          break;
+          default:
+            goto end;
+        }
+
+      commands_view->base_offset = native_slice_offset;
+    }
+  else
+    commands_view->base_offset = 0;
+
+  file_header = file_header_view.data;
+  commands_view->commands_count =
+      macho_file_to_host_u32 (commands_view->bytes_swapped,
+                              file_header->ncmds);
+  commands_view->commands_total_size =
+      macho_file_to_host_u32 (commands_view->bytes_swapped,
+                              file_header->sizeofcmds);
+  commands_offset =
+      commands_view->base_offset + sizeof (mach_header_native_t);
+
+  if (!backtrace_get_view (state, descriptor, commands_offset,
+                           commands_view->commands_total_size, error_callback,
+                           data, &commands_view->view))
+    goto end;
+
+  ret = 1;
+
+end:
+  if (file_header_view_valid)
+    backtrace_release_view (state, &file_header_view, error_callback, data);
+  if (fat_archs_view_valid)
+    backtrace_release_view (state, &fat_archs_view, error_callback, data);
+  return ret;
+}
+
+int
+macho_get_uuid (struct backtrace_state *state ATTRIBUTE_UNUSED,
+                int descriptor ATTRIBUTE_UNUSED,
+                backtrace_error_callback error_callback,
+                void *data, struct macho_commands_view *commands_view,
+                uuid_t *uuid)
+{
+  size_t offset = 0;
+  uint32_t i = 0;
+
+  for (i = 0; i < commands_view->commands_count; i++)
+    {
+      const struct load_command *raw_command;
+      struct load_command command;
+
+      if (offset + sizeof (struct load_command)
+          > commands_view->commands_total_size)
+        {
+          error_callback (data,
+                          "executable file contains out of range command offset",
+                          0);
+          return 0;
+        }
+
+      raw_command =
+          commands_view->view.data + offset;
+      command.cmd = macho_file_to_host_u32 (commands_view->bytes_swapped,
+                                            raw_command->cmd);
+      command.cmdsize = macho_file_to_host_u32 (commands_view->bytes_swapped,
+                                                raw_command->cmdsize);
+
+      if (command.cmd == LC_UUID)
+        {
+          const struct uuid_command *uuid_command;
+
+          if (offset + sizeof (struct uuid_command)
+              > commands_view->commands_total_size)
+            {
+              error_callback (data,
+                              "executable file contains out of range command offset",
+                              0);
+              return 0;
+            }
+
+          uuid_command =
+              (struct uuid_command *) raw_command;
+          memcpy (uuid, uuid_command->uuid, sizeof (uuid_t));
+          return 1;
+        }
+
+      offset += command.cmdsize;
+    }
+
+  error_callback (data, "executable file is missing an identifying UUID", 0);
+  return 0;
+}
+
+/* Returns the base address of a Mach-O image, as encoded in the file header.
+ * WARNING: This does not take ASLR into account, which is ubiquitous on recent
+ * Darwin platforms.
+ */
+int
+macho_get_addr_range (struct backtrace_state *state ATTRIBUTE_UNUSED,
+                      int descriptor ATTRIBUTE_UNUSED,
+                      backtrace_error_callback error_callback,
+                      void *data, struct macho_commands_view *commands_view,
+                      uintptr_t *base_address, uintptr_t *max_address)
+{
+  size_t offset = 0;
+  int found_text = 0;
+  uint32_t i = 0;
+
+  *max_address = 0;
+
+  for (i = 0; i < commands_view->commands_count; i++)
+    {
+      const struct load_command *raw_command;
+      struct load_command command;
+
+      if (offset + sizeof (struct load_command)
+          > commands_view->commands_total_size)
+        {
+          error_callback (data,
+                          "executable file contains out of range command offset",
+                          0);
+          return 0;
+        }
+
+      raw_command = commands_view->view.data + offset;
+      command.cmd = macho_file_to_host_u32 (commands_view->bytes_swapped,
+                                            raw_command->cmd);
+      command.cmdsize = macho_file_to_host_u32 (commands_view->bytes_swapped,
+                                                raw_command->cmdsize);
+
+      if (command.cmd == LC_SEGMENT_NATIVE)
+        {
+          const segment_command_native_t *raw_segment;
+          uintptr_t segment_vmaddr;
+          uintptr_t segment_vmsize;
+          uintptr_t segment_maxaddr;
+          uintptr_t text_fileoff;
+
+          if (offset + sizeof (segment_command_native_t)
+              > commands_view->commands_total_size)
+            {
+              error_callback (data,
+                              "executable file contains out of range command offset",
+                              0);
+              return 0;
+            }
+
+          raw_segment = (segment_command_native_t *) raw_command;
+
+          segment_vmaddr = macho_file_to_host_usize (
+              commands_view->bytes_swapped, raw_segment->vmaddr);
+          segment_vmsize = macho_file_to_host_usize (
+              commands_view->bytes_swapped, raw_segment->vmsize);
+          segment_maxaddr = segment_vmaddr + segment_vmsize;
+
+          if (strncmp (raw_segment->segname, "__TEXT",
+                       sizeof (raw_segment->segname)) == 0)
+            {
+              text_fileoff = macho_file_to_host_usize (
+                  commands_view->bytes_swapped, raw_segment->fileoff);
+              *base_address = segment_vmaddr - text_fileoff;
+
+              found_text = 1;
+            }
+
+          if (segment_maxaddr > *max_address)
+            *max_address = segment_maxaddr;
+        }
+
+      offset += command.cmdsize;
+    }
+
+  if (found_text)
+    return 1;
+  else
+    {
+      error_callback (data, "executable is missing __TEXT segment", 0);
+      return 0;
+    }
+}
+
+static int
+macho_symbol_compare_addr (const void *left_raw, const void *right_raw)
+{
+  const struct macho_symbol *left = left_raw;
+  const struct macho_symbol *right = right_raw;
+
+  if (left->addr > right->addr)
+    return 1;
+  else if (left->addr < right->addr)
+    return -1;
+  else
+    return 0;
+}
+
+int
+macho_symbol_type_relevant (uint8_t type)
+{
+  uint8_t type_field = (uint8_t) (type & N_TYPE);
+
+  return !(type & N_EXT) &&
+         (type_field == N_ABS || type_field == N_SECT);
+}
+
+int
+macho_add_symtab (struct backtrace_state *state,
+                  backtrace_error_callback error_callback,
+                  void *data, int descriptor,
+                  struct macho_commands_view *commands_view,
+                  uintptr_t base_address, uintptr_t max_image_address,
+                  intptr_t vmslide, int *found_sym)
+{
+  struct macho_syminfo_data *syminfo_data;
+
+  int ret = 0;
+  size_t offset = 0;
+  struct backtrace_view symtab_view;
+  int symtab_view_valid = 0;
+  struct backtrace_view strtab_view;
+  int strtab_view_valid = 0;
+  size_t syminfo_index = 0;
+  size_t function_count = 0;
+  uint32_t i = 0;
+  uint32_t j = 0;
+  uint32_t symtab_index = 0;
+
+  *found_sym = 0;
+
+  for (i = 0; i < commands_view->commands_count; i++)
+    {
+      const struct load_command *raw_command;
+      struct load_command command;
+
+      if (offset + sizeof (struct load_command)
+          > commands_view->commands_total_size)
+        {
+          error_callback (data,
+                          "executable file contains out of range command offset",
+                          0);
+          return 0;
+        }
+
+      raw_command = commands_view->view.data + offset;
+      command.cmd = macho_file_to_host_u32 (commands_view->bytes_swapped,
+                                            raw_command->cmd);
+      command.cmdsize = macho_file_to_host_u32 (commands_view->bytes_swapped,
+                                                raw_command->cmdsize);
+
+      if (command.cmd == LC_SYMTAB)
+        {
+          const struct symtab_command *symtab_command;
+          uint32_t symbol_table_offset;
+          uint32_t symbol_count;
+          uint32_t string_table_offset;
+          uint32_t string_table_size;
+
+          if (offset + sizeof (struct symtab_command)
+              > commands_view->commands_total_size)
+            {
+              error_callback (data,
+                              "executable file contains out of range command offset",
+                              0);
+              return 0;
+            }
+
+          symtab_command = (struct symtab_command *) raw_command;
+
+          symbol_table_offset = macho_file_to_host_u32 (
+              commands_view->bytes_swapped, symtab_command->symoff);
+          symbol_count = macho_file_to_host_u32 (
+              commands_view->bytes_swapped, symtab_command->nsyms);
+          string_table_offset = macho_file_to_host_u32 (
+              commands_view->bytes_swapped, symtab_command->stroff);
+          string_table_size = macho_file_to_host_u32 (
+              commands_view->bytes_swapped, symtab_command->strsize);
+
+
+          if (!macho_get_view (state, descriptor, symbol_table_offset,
+                               symbol_count * sizeof (nlist_native_t),
+                               error_callback, data, commands_view,
+                               &symtab_view))
+            goto end;
+          symtab_view_valid = 1;
+
+          if (!macho_get_view (state, descriptor, string_table_offset,
+                               string_table_size, error_callback, data,
+                               commands_view, &strtab_view))
+            goto end;
+          strtab_view_valid = 1;
+
+          // Count functions first
+          for (j = 0; j < symbol_count; j++)
+            {
+              const nlist_native_t *raw_sym =
+                  ((const nlist_native_t *) symtab_view.data) + j;
+
+              if (macho_symbol_type_relevant (raw_sym->n_type))
+                {
+                  function_count += 1;
+                }
+            }
+
+          // Allocate space for the:
+          //  (a) macho_syminfo_data for this image
+          //  (b) macho_symbol entries
+          syminfo_data =
+              backtrace_alloc (state,
+                               sizeof (struct macho_syminfo_data),
+                               error_callback, data);
+          if (syminfo_data == NULL)
+            goto end;
+
+          syminfo_data->symbols = backtrace_alloc (
+              state, function_count * sizeof (struct macho_symbol),
+              error_callback, data);
+          if (syminfo_data->symbols == NULL)
+            goto end;
+
+          syminfo_data->symbol_count = function_count;
+          syminfo_data->next = NULL;
+          syminfo_data->min_addr = base_address;
+          syminfo_data->max_addr = max_image_address;
+
+          for (symtab_index = 0;
+               symtab_index < symbol_count; symtab_index++)
+            {
+              const nlist_native_t *raw_sym =
+                  ((const nlist_native_t *) symtab_view.data) +
+                  symtab_index;
+
+              if (macho_symbol_type_relevant (raw_sym->n_type))
+                {
+                  size_t strtab_index;
+                  const char *name;
+                  size_t max_len_plus_one;
+
+                  syminfo_data->symbols[syminfo_index].addr =
+                      macho_file_to_host_usize (commands_view->bytes_swapped,
+                                                raw_sym->n_value) + vmslide;
+
+                  strtab_index = macho_file_to_host_u32 (
+                      commands_view->bytes_swapped,
+                      raw_sym->n_un.n_strx);
+
+                  // Check the range of the supposed "string" we've been
+                  // given
+                  if (strtab_index >= string_table_size)
+                    {
+                      error_callback (
+                          data,
+                          "dSYM file contains out of range string table index",
+                          0);
+                      goto end;
+                    }
+
+                  name = strtab_view.data + strtab_index;
+                  max_len_plus_one = string_table_size - strtab_index;
+
+                  if (strnlen (name, max_len_plus_one) >= max_len_plus_one)
+                    {
+                      error_callback (
+                          data,
+                          "dSYM file contains unterminated string",
+                          0);
+                      goto end;
+                    }
+
+                  // Remove underscore prefixes
+                  if (name[0] == '_')
+                    {
+                      name = name + 1;
+                    }
+
+                  syminfo_data->symbols[syminfo_index].name = name;
+
+                  syminfo_index += 1;
+                }
+            }
+
+          backtrace_qsort (syminfo_data->symbols,
+                           syminfo_data->symbol_count,
+                           sizeof (struct macho_symbol),
+                           macho_symbol_compare_addr);
+
+          // Calculate symbol sizes
+          for (syminfo_index = 0;
+               syminfo_index < syminfo_data->symbol_count; syminfo_index++)
+            {
+              if (syminfo_index + 1 < syminfo_data->symbol_count)
+                {
+                  syminfo_data->symbols[syminfo_index].size =
+                      syminfo_data->symbols[syminfo_index + 1].addr -
+                      syminfo_data->symbols[syminfo_index].addr;
+                }
+              else
+                {
+                  syminfo_data->symbols[syminfo_index].size =
+                      max_image_address -
+                      syminfo_data->symbols[syminfo_index].addr;
+                }
+            }
+
+          if (!state->threaded)
+            {
+              struct macho_syminfo_data **pp;
+
+              for (pp = (struct macho_syminfo_data **) (void *) &state->syminfo_data;
+                   *pp != NULL;
+                   pp = &(*pp)->next);
+              *pp = syminfo_data;
+            }
+          else
+            {
+              while (1)
+                {
+                  struct macho_syminfo_data **pp;
+
+                  pp = (struct macho_syminfo_data **) (void *) &state->syminfo_data;
+
+                  while (1)
+                    {
+                      struct macho_syminfo_data *p;
+
+                      p = backtrace_atomic_load_pointer (pp);
+
+                      if (p == NULL)
+                        break;
+
+                      pp = &p->next;
+                    }
+
+                  if (__sync_bool_compare_and_swap (pp, NULL, syminfo_data))
+                    break;
+                }
+            }
+
+          strtab_view_valid = 0; // We need to keep string table around
+          *found_sym = 1;
+          ret = 1;
+          goto end;
+        }
+
+      offset += command.cmdsize;
+    }
+
+  // No symbol table here
+  ret = 1;
+  goto end;
+
+end:
+  if (symtab_view_valid)
+    backtrace_release_view (state, &symtab_view, error_callback, data);
+  if (strtab_view_valid)
+    backtrace_release_view (state, &strtab_view, error_callback, data);
+  return ret;
+}
+
+int
+macho_try_dwarf (struct backtrace_state *state,
+                 backtrace_error_callback error_callback,
+                 void *data, fileline *fileline_fn, uuid_t *executable_uuid,
+                 uintptr_t base_address, uintptr_t max_image_address,
+                 intptr_t vmslide, char *dwarf_filename, int *matched,
+                 int *found_sym, int *found_dwarf)
+{
+  uuid_t dwarf_uuid;
+
+  int ret = 0;
+  int dwarf_descriptor;
+  int dwarf_descriptor_valid = 0;
+  struct macho_commands_view commands_view;
+  int commands_view_valid = 0;
+  struct backtrace_view dwarf_view;
+  int dwarf_view_valid = 0;
+  size_t offset = 0;
+  struct found_dwarf_section dwarf_sections[DEBUG_MAX];
+  uintptr_t min_dwarf_offset = 0;
+  uintptr_t max_dwarf_offset = 0;
+  uint32_t i = 0;
+  uint32_t j = 0;
+  int k = 0;
+
+  *matched = 0;
+  *found_sym = 0;
+  *found_dwarf = 0;
+
+  if ((dwarf_descriptor = backtrace_open (dwarf_filename, error_callback,
+                                          data, NULL)) == 0)
+    goto end;
+  dwarf_descriptor_valid = 1;
+
+  int incompatible;
+  if (!macho_get_commands (state, dwarf_descriptor, error_callback, data,
+                           &commands_view, &incompatible))
+    {
+      // Failing to read the header here is fine, because this dSYM may be
+      // for a different architecture
+      if (incompatible)
+        {
+          ret = 1;
+        }
+      goto end;
+    }
+  commands_view_valid = 1;
+
+  // Get dSYM UUID and compare
+  if (!macho_get_uuid (state, dwarf_descriptor, error_callback, data,
+                       &commands_view, &dwarf_uuid))
+    {
+      error_callback (data, "dSYM file is missing an identifying uuid", 0);
+      goto end;
+    }
+  if (memcmp (executable_uuid, &dwarf_uuid, sizeof (uuid_t)) != 0)
+    {
+      // DWARF doesn't belong to desired executable
+      ret = 1;
+      goto end;
+    }
+
+  *matched = 1;
+
+  // Read symbol table
+  if (!macho_add_symtab (state, error_callback, data, dwarf_descriptor,
+                         &commands_view, base_address, max_image_address,
+                         vmslide, found_sym))
+    goto end;
+
+  // Get DWARF sections
+
+  memset (dwarf_sections, 0, sizeof (dwarf_sections));
+  offset = 0;
+  for (i = 0; i < commands_view.commands_count; i++)
+    {
+      const struct load_command *raw_command;
+      struct load_command command;
+
+      if (offset + sizeof (struct load_command)
+          > commands_view.commands_total_size)
+        {
+          error_callback (data,
+                          "dSYM file contains out of range command offset", 0);
+          goto end;
+        }
+
+      raw_command = commands_view.view.data + offset;
+      command.cmd = macho_file_to_host_u32 (commands_view.bytes_swapped,
+                                            raw_command->cmd);
+      command.cmdsize = macho_file_to_host_u32 (commands_view.bytes_swapped,
+                                                raw_command->cmdsize);
+
+      if (command.cmd == LC_SEGMENT_NATIVE)
+        {
+          uint32_t section_count;
+          size_t section_offset;
+          const segment_command_native_t *raw_segment;
+
+          if (offset + sizeof (segment_command_native_t)
+              > commands_view.commands_total_size)
+            {
+              error_callback (data,
+                              "dSYM file contains out of range command offset",
+                              0);
+              goto end;
+            }
+
+          raw_segment = (const segment_command_native_t *) raw_command;
+
+          if (strncmp (raw_segment->segname, "__DWARF",
+                       sizeof (raw_segment->segname)) == 0)
+            {
+              section_count = macho_file_to_host_u32 (
+                  commands_view.bytes_swapped,
+                  raw_segment->nsects);
+
+              section_offset = offset + sizeof (segment_command_native_t);
+
+              // Search sections for relevant DWARF section names
+              for (j = 0; j < section_count; j++)
+                {
+                  const section_native_t *raw_section;
+
+                  if (section_offset + sizeof (section_native_t) >
+                      commands_view.commands_total_size)
+                    {
+                      error_callback (data,
+                                      "dSYM file contains out of range command offset",
+                                      0);
+                      goto end;
+                    }
+
+                  raw_section = commands_view.view.data + section_offset;
+
+                  for (k = 0; k < DEBUG_MAX; k++)
+                    {
+                      uintptr_t dwarf_section_end;
+
+                      if (strncmp (raw_section->sectname,
+                                   debug_section_names[k],
+                                   sizeof (raw_section->sectname)) == 0)
+                        {
+                          *found_dwarf = 1;
+
+                          dwarf_sections[k].file_offset =
+                              macho_file_to_host_u32 (
+                                  commands_view.bytes_swapped,
+                                  raw_section->offset);
+                          dwarf_sections[k].file_size =
+                              macho_file_to_host_usize (
+                                  commands_view.bytes_swapped,
+                                  raw_section->size);
+
+                          if (min_dwarf_offset == 0 ||
+                              dwarf_sections[k].file_offset <
+                              min_dwarf_offset)
+                            min_dwarf_offset = dwarf_sections[k].file_offset;
+
+                          dwarf_section_end =
+                              dwarf_sections[k].file_offset +
+                              dwarf_sections[k].file_size;
+                          if (dwarf_section_end > max_dwarf_offset)
+                            max_dwarf_offset = dwarf_section_end;
+
+                          break;
+                        }
+                    }
+
+                  section_offset += sizeof (section_native_t);
+                }
+
+              break;
+            }
+        }
+
+      offset += command.cmdsize;
+    }
+
+  if (!*found_dwarf)
+    {
+      // No DWARF in this file
+      ret = 1;
+      goto end;
+    }
+
+  if (!macho_get_view (state, dwarf_descriptor, (off_t) min_dwarf_offset,
+                       max_dwarf_offset - min_dwarf_offset, error_callback,
+                       data, &commands_view, &dwarf_view))
+    goto end;
+  dwarf_view_valid = 1;
+
+  for (i = 0; i < DEBUG_MAX; i++)
+    {
+      if (dwarf_sections[i].file_offset == 0)
+        dwarf_sections[i].data = NULL;
+      else
+        dwarf_sections[i].data =
+            dwarf_view.data + dwarf_sections[i].file_offset - min_dwarf_offset;
+    }
+
+  if (!backtrace_dwarf_add (state, vmslide,
+                            dwarf_sections[DEBUG_INFO].data,
+                            dwarf_sections[DEBUG_INFO].file_size,
+                            dwarf_sections[DEBUG_LINE].data,
+                            dwarf_sections[DEBUG_LINE].file_size,
+                            dwarf_sections[DEBUG_ABBREV].data,
+                            dwarf_sections[DEBUG_ABBREV].file_size,
+                            dwarf_sections[DEBUG_RANGES].data,
+                            dwarf_sections[DEBUG_RANGES].file_size,
+                            dwarf_sections[DEBUG_STR].data,
+                            dwarf_sections[DEBUG_STR].file_size,
+                            ((__DARWIN_BYTE_ORDER == __DARWIN_BIG_ENDIAN)
+                            ^ commands_view.bytes_swapped),
+                            error_callback, data, fileline_fn))
+    goto end;
+
+  // Don't release the DWARF view because it is still in use
+  dwarf_descriptor_valid = 0;
+  dwarf_view_valid = 0;
+  ret = 1;
+
+end:
+  if (dwarf_descriptor_valid)
+    backtrace_close (dwarf_descriptor, error_callback, data);
+  if (commands_view_valid)
+    backtrace_release_view (state, &commands_view.view, error_callback, data);
+  if (dwarf_view_valid)
+    backtrace_release_view (state, &dwarf_view, error_callback, data);
+  return ret;
+}
+
+int
+macho_try_dsym (struct backtrace_state *state,
+                backtrace_error_callback error_callback,
+                void *data, fileline *fileline_fn, uuid_t *executable_uuid,
+                uintptr_t base_address, uintptr_t max_image_address,
+                intptr_t vmslide, char *dsym_filename, int *matched,
+                int *found_sym, int *found_dwarf)
+{
+  int ret = 0;
+  char dwarf_image_dir_path[PATH_MAX];
+  DIR *dwarf_image_dir;
+  int dwarf_image_dir_valid = 0;
+  struct dirent *directory_entry;
+  char dwarf_filename[PATH_MAX];
+  int dwarf_matched;
+  int dwarf_had_sym;
+  int dwarf_had_dwarf;
+
+  *matched = 0;
+  *found_sym = 0;
+  *found_dwarf = 0;
+
+  strncpy (dwarf_image_dir_path, dsym_filename, PATH_MAX);
+  strncat (dwarf_image_dir_path, "/Contents/Resources/DWARF", PATH_MAX);
+
+  if (!(dwarf_image_dir = opendir (dwarf_image_dir_path)))
+    {
+      error_callback (data, "could not open DWARF directory in dSYM",
+                      0);
+      goto end;
+    }
+  dwarf_image_dir_valid = 1;
+
+  while ((directory_entry = readdir (dwarf_image_dir)))
+    {
+      if (directory_entry->d_type != DT_REG)
+        continue;
+
+      strncpy (dwarf_filename, dwarf_image_dir_path, PATH_MAX);
+      strncat (dwarf_filename, "/", PATH_MAX);
+      strncat (dwarf_filename, directory_entry->d_name, PATH_MAX);
+
+      if (!macho_try_dwarf (state, error_callback, data, fileline_fn,
+                            executable_uuid, base_address, max_image_address,
+                            vmslide, dwarf_filename,
+                            &dwarf_matched, &dwarf_had_sym, &dwarf_had_dwarf))
+        goto end;
+
+      if (dwarf_matched)
+        {
+          *matched = 1;
+          *found_sym = dwarf_had_sym;
+          *found_dwarf = dwarf_had_dwarf;
+          ret = 1;
+          goto end;
+        }
+    }
+
+  // No matching DWARF in this dSYM
+  ret = 1;
+  goto end;
+
+end:
+  if (dwarf_image_dir_valid)
+    closedir (dwarf_image_dir);
+  return ret;
+}
+
+int
+macho_add (struct backtrace_state *state,
+           backtrace_error_callback error_callback, void *data, int descriptor,
+           const char *filename, fileline *fileline_fn, intptr_t vmslide,
+           int *found_sym, int *found_dwarf)
+{
+  uuid_t image_uuid;
+  uintptr_t image_file_base_address;
+  uintptr_t image_file_max_address;
+  uintptr_t image_actual_base_address = 0;
+  uintptr_t image_actual_max_address = 0;
+
+  int ret = 0;
+  struct macho_commands_view commands_view;
+  int commands_view_valid = 0;
+  char executable_dirname[PATH_MAX];
+  size_t filename_len;
+  DIR *executable_dir = NULL;
+  int executable_dir_valid = 0;
+  struct dirent *directory_entry;
+  char dsym_full_path[PATH_MAX];
+  static const char *extension;
+  size_t extension_len;
+  ssize_t i;
+
+  *found_sym = 0;
+  *found_dwarf = 0;
+
+  // Find Mach-O commands list
+  int incompatible;
+  if (!macho_get_commands (state, descriptor, error_callback, data,
+                           &commands_view, &incompatible))
+    goto end;
+  commands_view_valid = 1;
+
+  // First we need to get the uuid of our file so we can hunt down the correct
+  // dSYM
+  if (!macho_get_uuid (state, descriptor, error_callback, data, &commands_view,
+                       &image_uuid))
+    goto end;
+
+  // Now we need to find the in memory base address. Step one is to find out
+  // what the executable thinks the base address is
+  if (!macho_get_addr_range (state, descriptor, error_callback, data,
+                             &commands_view,
+                             &image_file_base_address,
+                             &image_file_max_address))
+    goto end;
+
+  image_actual_base_address =
+      image_file_base_address + vmslide;
+  image_actual_max_address =
+      image_file_max_address + vmslide;
+
+  if (image_actual_base_address == 0)
+    {
+      error_callback (data, "executable file is not loaded", 0);
+      goto end;
+    }
+
+  // Look for dSYM in our executable's directory
+  strncpy (executable_dirname, filename, PATH_MAX);
+  filename_len = strlen (executable_dirname);
+  for (i = filename_len - 1; i >= 0; i--)
+    {
+      if (executable_dirname[i] == '/')
+        {
+          executable_dirname[i] = '\0';
+          break;
+        }
+      else if (i == 0)
+        {
+          executable_dirname[0] = '.';
+          executable_dirname[1] = '\0';
+          break;
+        }
+    }
+
+  if (!(executable_dir = opendir (executable_dirname)))
+    {
+      error_callback (data, "could not open directory containing executable",
+                      0);
+      goto end;
+    }
+  executable_dir_valid = 1;
+
+  extension = ".dSYM";
+  extension_len = strlen (extension);
+  while ((directory_entry = readdir (executable_dir)))
+    {
+      if (directory_entry->d_namlen < extension_len)
+        continue;
+      if (strncasecmp (directory_entry->d_name + directory_entry->d_namlen
+                       - extension_len, extension, extension_len) == 0)
+        {
+          int matched;
+          int dsym_had_sym;
+          int dsym_had_dwarf;
+
+          // Found a dSYM
+          strncpy (dsym_full_path, executable_dirname, PATH_MAX);
+          strncat (dsym_full_path, "/", PATH_MAX);
+          strncat (dsym_full_path, directory_entry->d_name, PATH_MAX);
+
+          if (!macho_try_dsym (state, error_callback, data,
+                               fileline_fn, &image_uuid,
+                               image_actual_base_address,
+                               image_actual_max_address, vmslide,
+                               dsym_full_path,
+                               &matched, &dsym_had_sym, &dsym_had_dwarf))
+            goto end;
+
+          if (matched)
+            {
+              *found_sym = dsym_had_sym;
+              *found_dwarf = dsym_had_dwarf;
+              ret = 1;
+              goto end;
+            }
+        }
+    }
+
+  // No matching dSYM
+  ret = 1;
+  goto end;
+
+end:
+  if (commands_view_valid)
+    backtrace_release_view (state, &commands_view.view, error_callback,
+                            data);
+  if (executable_dir_valid)
+    closedir (executable_dir);
+  return ret;
+}
+
+static int
+macho_symbol_search (const void *vkey, const void *ventry)
+{
+  const uintptr_t *key = (const uintptr_t *) vkey;
+  const struct macho_symbol *entry = (const struct macho_symbol *) ventry;
+  uintptr_t addr;
+
+  addr = *key;
+  if (addr < entry->addr)
+    return -1;
+  else if (addr >= entry->addr + entry->size)
+    return 1;
+  else
+    return 0;
+}
+
+static void
+macho_syminfo (struct backtrace_state *state,
+               uintptr_t addr,
+               backtrace_syminfo_callback callback,
+               backtrace_error_callback error_callback ATTRIBUTE_UNUSED,
+               void *data)
+{
+  struct macho_syminfo_data *edata;
+  struct macho_symbol *sym = NULL;
+
+  if (!state->threaded)
+    {
+      for (edata = (struct macho_syminfo_data *) state->syminfo_data;
+           edata != NULL;
+           edata = edata->next)
+        {
+          if (addr >= edata->min_addr && addr <= edata->max_addr)
+            {
+              sym = ((struct macho_symbol *)
+                  bsearch (&addr, edata->symbols, edata->symbol_count,
+                           sizeof (struct macho_symbol), macho_symbol_search));
+              if (sym != NULL)
+                break;
+            }
+        }
+    }
+  else
+    {
+      struct macho_syminfo_data **pp;
+
+      pp = (struct macho_syminfo_data **) (void *) &state->syminfo_data;
+      while (1)
+        {
+          edata = backtrace_atomic_load_pointer (pp);
+          if (edata == NULL)
+            break;
+
+          if (addr >= edata->min_addr && addr <= edata->max_addr)
+            {
+              sym = ((struct macho_symbol *)
+                  bsearch (&addr, edata->symbols, edata->symbol_count,
+                           sizeof (struct macho_symbol), macho_symbol_search));
+              if (sym != NULL)
+                break;
+            }
+
+          pp = &edata->next;
+        }
+    }
+
+  if (sym == NULL)
+    callback (data, addr, NULL, 0, 0);
+  else
+    callback (data, addr, sym->name, sym->addr, sym->size);
+}
+
+
+static int
+macho_nodebug (struct backtrace_state *state ATTRIBUTE_UNUSED,
+               uintptr_t pc ATTRIBUTE_UNUSED,
+               backtrace_full_callback callback ATTRIBUTE_UNUSED,
+               backtrace_error_callback error_callback, void *data)
+{
+  error_callback (data, "no debug info in Mach-O executable", -1);
+  return 0;
+}
+
+static void
+macho_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
+              uintptr_t addr ATTRIBUTE_UNUSED,
+              backtrace_syminfo_callback callback ATTRIBUTE_UNUSED,
+              backtrace_error_callback error_callback, void *data)
+{
+  error_callback (data, "no symbol table in Mach-O executable", -1);
+}
+
+int
+backtrace_initialize (struct backtrace_state *state,
+                      const char *filename,
+                      int descriptor,
+                      backtrace_error_callback error_callback,
+                      void *data, fileline *fileline_fn)
+{
+  int ret;
+  fileline macho_fileline_fn = macho_nodebug;
+  int found_sym = 0;
+  int found_dwarf = 0;
+  uint32_t i = 0;
+  uint32_t loaded_image_count;
+
+  // Add all loaded images
+  loaded_image_count = _dyld_image_count ();
+  for (i = 0; i < loaded_image_count; i++)
+    {
+      int current_found_sym;
+      int current_found_dwarf;
+      int current_descriptor;
+      intptr_t current_vmslide;
+      const char *current_name;
+
+      current_vmslide = _dyld_get_image_vmaddr_slide (i);
+      current_name = _dyld_get_image_name (i);
+
+      if (current_name == NULL || (i != 0 && current_vmslide == 0))
+        continue;
+
+      if (!(current_descriptor =
+                backtrace_open (current_name, error_callback, data, NULL)))
+        {
+          continue;
+        }
+
+      if (macho_add (state, error_callback, data, current_descriptor,
+                      current_name, &macho_fileline_fn, current_vmslide,
+                      &current_found_sym, &current_found_dwarf))
+        {
+          found_sym = found_sym || current_found_sym;
+          found_dwarf = found_dwarf || current_found_dwarf;
+        }
+
+      backtrace_close (current_descriptor, error_callback, data);
+    }
+
+  if (!state->threaded)
+    {
+      if (found_sym)
+        state->syminfo_fn = macho_syminfo;
+      else if (state->syminfo_fn == NULL)
+        state->syminfo_fn = macho_nosyms;
+    }
+  else
+    {
+      if (found_sym)
+        backtrace_atomic_store_pointer (&state->syminfo_fn, macho_syminfo);
+      else
+        (void) __sync_bool_compare_and_swap (&state->syminfo_fn, NULL,
+                                             macho_nosyms);
+    }
+
+  if (!state->threaded)
+    {
+      if (state->fileline_fn == NULL || state->fileline_fn == macho_nodebug)
+        *fileline_fn = macho_fileline_fn;
+    }
+  else
+    {
+      fileline current_fn;
+
+      current_fn = backtrace_atomic_load_pointer (&state->fileline_fn);
+      if (current_fn == NULL || current_fn == macho_nodebug)
+        *fileline_fn = macho_fileline_fn;
+    }
+
+  return 1;
+}
+