Import google-glog's Symbolize() and use it in debug_util_posix.cc.

base/third_party/symbolize/symbolize.cc

+// Copyright (c) 2006, Google Inc.
+// 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.
+//
+// Author: Satoru Takabayashi
+// Stack-footprint reduction work done by Raksit Ashok
+//
+// Implementation note:
+//
+// We don't use heaps but only use stacks.  We want to reduce the
+// stack consumption so that the symbolizer can run on small stacks.
+//
+// Here are some numbers collected with GCC 4.1.0 on x86:
+// - sizeof(Elf32_Sym)  = 16
+// - sizeof(Elf32_Shdr) = 40
+// - sizeof(Elf64_Sym)  = 24
+// - sizeof(Elf64_Shdr) = 64
+//
+// This implementation is intended to be async-signal-safe but uses
+// some functions which are not guaranteed to be so, such as memchr()
+// and memmove().  We assume they are async-signal-safe.
+//
+
+#include "utilities.h"
+
+#if defined(HAVE_SYMBOLIZE)
+
+#include <limits>
+
+#include "symbolize.h"
+#include "demangle.h"
+
+_START_GOOGLE_NAMESPACE_
+
+// We don't use assert() since it's not guaranteed to be
+// async-signal-safe.  Instead we define a minimal assertion
+// macro. So far, we don't need pretty printing for __FILE__, etc.
+
+// A wrapper for abort() to make it callable in ? :.
+static int AssertFail() {
+  abort();
+  return 0;  // Should not reach.
+}
+
+#define SAFE_ASSERT(expr) ((expr) ? 0 : AssertFail())
+
+static SymbolizeCallback g_symbolize_callback = NULL;
+void InstallSymbolizeCallback(SymbolizeCallback callback) {
+  g_symbolize_callback = callback;
+}
+
+// This function wraps the Demangle function to provide an interface
+// where the input symbol is demangled in-place.
+// To keep stack consumption low, we would like this function to not
+// get inlined.
+static ATTRIBUTE_NOINLINE void DemangleInplace(char *out, int out_size) {
+  char demangled[256];  // Big enough for sane demangled symbols.
+  if (Demangle(out, demangled, sizeof(demangled))) {
+    // Demangling succeeded. Copy to out if the space allows.
+    int len = strlen(demangled);
+    if (len + 1 <= out_size) {  // +1 for '\0'.
+      SAFE_ASSERT(len < sizeof(demangled));
+      memmove(out, demangled, len + 1);
+    }
+  }
+}
+
+_END_GOOGLE_NAMESPACE_
+
+#if defined(__ELF__)
+
+#include <dlfcn.h>
+#include <elf.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <link.h>  // For ElfW() macro.
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "symbolize.h"
+#include "config.h"
+#include "glog/raw_logging.h"
+
+// Re-runs fn until it doesn't cause EINTR.
+#define NO_INTR(fn)   do {} while ((fn) < 0 && errno == EINTR)
+
+_START_GOOGLE_NAMESPACE_
+
+// Read up to "count" bytes from file descriptor "fd" into the buffer
+// starting at "buf" while handling short reads and EINTR.  On
+// success, return the number of bytes read.  Otherwise, return -1.
+static ssize_t ReadPersistent(const int fd, void *buf, const size_t count) {
+  SAFE_ASSERT(fd >= 0);
+  SAFE_ASSERT(count >= 0 && count <= std::numeric_limits<ssize_t>::max());
+  char *buf0 = reinterpret_cast<char *>(buf);
+  ssize_t num_bytes = 0;
+  while (num_bytes < count) {
+    ssize_t len;
+    NO_INTR(len = read(fd, buf0 + num_bytes, count - num_bytes));
+    if (len < 0) {  // There was an error other than EINTR.
+      return -1;
+    }
+    if (len == 0) {  // Reached EOF.
+      break;
+    }
+    num_bytes += len;
+  }
+  SAFE_ASSERT(num_bytes <= count);
+  return num_bytes;
+}
+
+// Read up to "count" bytes from "offset" in the file pointed by file
+// descriptor "fd" into the buffer starting at "buf".  On success,
+// return the number of bytes read.  Otherwise, return -1.
+static ssize_t ReadFromOffset(const int fd, void *buf,
+                              const size_t count, const off_t offset) {
+  off_t off = lseek(fd, offset, SEEK_SET);
+  if (off == (off_t)-1) {
+    return -1;
+  }
+  return ReadPersistent(fd, buf, count);
+}
+
+// Try reading exactly "count" bytes from "offset" bytes in a file
+// pointed by "fd" into the buffer starting at "buf" while handling
+// short reads and EINTR.  On success, return true. Otherwise, return
+// false.
+static bool ReadFromOffsetExact(const int fd, void *buf,
+                                const size_t count, const off_t offset) {
+  ssize_t len = ReadFromOffset(fd, buf, count, offset);
+  return len == count;
+}
+
+// Returns elf_header.e_type if the file pointed by fd is an ELF binary.
+static int FileGetElfType(const int fd) {
+  ElfW(Ehdr) elf_header;
+  if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
+    return -1;
+  }
+  if (memcmp(elf_header.e_ident, ELFMAG, SELFMAG) != 0) {
+    return -1;
+  }
+  return elf_header.e_type;
+}
+
+// Read the section headers in the given ELF binary, and if a section
+// of the specified type is found, set the output to this section header
+// and return true.  Otherwise, return false.
+// To keep stack consumption low, we would like this function to not get
+// inlined.
+static ATTRIBUTE_NOINLINE bool
+GetSectionHeaderByType(const int fd, ElfW(Half) sh_num, const off_t sh_offset,
+                       ElfW(Word) type, ElfW(Shdr) *out) {
+  // Read at most 16 section headers at a time to save read calls.
+  ElfW(Shdr) buf[16];
+  for (int i = 0; i < sh_num;) {
+    const ssize_t num_bytes_left = (sh_num - i) * sizeof(buf[0]);
+    const ssize_t num_bytes_to_read =
+        (sizeof(buf) > num_bytes_left) ? num_bytes_left : sizeof(buf);
+    const ssize_t len = ReadFromOffset(fd, buf, num_bytes_to_read,
+                                       sh_offset + i * sizeof(buf[0]));
+    SAFE_ASSERT(len % sizeof(buf[0]) == 0);
+    const ssize_t num_headers_in_buf = len / sizeof(buf[0]);
+    SAFE_ASSERT(num_headers_in_buf <= sizeof(buf) / sizeof(buf[0]));
+    for (int j = 0; j < num_headers_in_buf; ++j) {
+      if (buf[j].sh_type == type) {
+        *out = buf[j];
+        return true;
+      }
+    }
+    i += num_headers_in_buf;
+  }
+  return false;
+}
+
+// There is no particular reason to limit section name to 63 characters,
+// but there has (as yet) been no need for anything longer either.
+const int kMaxSectionNameLen = 64;
+
+// name_len should include terminating '\0'.
+bool GetSectionHeaderByName(int fd, const char *name, size_t name_len,
+                            ElfW(Shdr) *out) {
+  ElfW(Ehdr) elf_header;
+  if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
+    return false;
+  }
+
+  ElfW(Shdr) shstrtab;
+  off_t shstrtab_offset = (elf_header.e_shoff +
+                           elf_header.e_shentsize * elf_header.e_shstrndx);
+  if (!ReadFromOffsetExact(fd, &shstrtab, sizeof(shstrtab), shstrtab_offset)) {
+    return false;
+  }
+
+  for (int i = 0; i < elf_header.e_shnum; ++i) {
+    off_t section_header_offset = (elf_header.e_shoff +
+                                   elf_header.e_shentsize * i);
+    if (!ReadFromOffsetExact(fd, out, sizeof(*out), section_header_offset)) {
+      return false;
+    }
+    char header_name[kMaxSectionNameLen];
+    if (sizeof(header_name) < name_len) {
+      RAW_LOG(WARNING, "Section name '%s' is too long (%"PRIuS"); "
+              "section will not be found (even if present).", name, name_len);
+      // No point in even trying.
+      return false;
+    }
+    off_t name_offset = shstrtab.sh_offset + out->sh_name;
+    ssize_t n_read = ReadFromOffset(fd, &header_name, name_len, name_offset);
+    if (n_read == -1) {
+      return false;
+    } else if (n_read != name_len) {
+      // Short read -- name could be at end of file.
+      continue;
+    }
+    if (memcmp(header_name, name, name_len) == 0) {
+      return true;
+    }
+  }
+  return false;
+}
+
+// Read a symbol table and look for the symbol containing the
+// pc. Iterate over symbols in a symbol table and look for the symbol
+// containing "pc".  On success, return true and write the symbol name
+// to out.  Otherwise, return false.
+// To keep stack consumption low, we would like this function to not get
+// inlined.
+static ATTRIBUTE_NOINLINE bool
+FindSymbol(uint64_t pc, const int fd, char *out, int out_size,
+           uint64_t symbol_offset, const ElfW(Shdr) *strtab,
+           const ElfW(Shdr) *symtab) {
+  if (symtab == NULL) {
+    return false;
+  }
+  const int num_symbols = symtab->sh_size / symtab->sh_entsize;
+  for (int i = 0; i < num_symbols;) {
+    off_t offset = symtab->sh_offset + i * symtab->sh_entsize;
+
+    // If we are reading Elf64_Sym's, we want to limit this array to
+    // 32 elements (to keep stack consumption low), otherwise we can
+    // have a 64 element Elf32_Sym array.
+#if __WORDSIZE == 64
+#define NUM_SYMBOLS 32
+#else
+#define NUM_SYMBOLS 64
+#endif
+
+    // Read at most NUM_SYMBOLS symbols at once to save read() calls.
+    ElfW(Sym) buf[NUM_SYMBOLS];
+    const ssize_t len = ReadFromOffset(fd, &buf, sizeof(buf), offset);
+    SAFE_ASSERT(len % sizeof(buf[0]) == 0);
+    const ssize_t num_symbols_in_buf = len / sizeof(buf[0]);
+    SAFE_ASSERT(num_symbols_in_buf <= sizeof(buf)/sizeof(buf[0]));
+    for (int j = 0; j < num_symbols_in_buf; ++j) {
+      const ElfW(Sym)& symbol = buf[j];
+      uint64_t start_address = symbol.st_value;
+      start_address += symbol_offset;
+      uint64_t end_address = start_address + symbol.st_size;
+      if (symbol.st_value != 0 &&  // Skip null value symbols.
+          symbol.st_shndx != 0 &&  // Skip undefined symbols.
+          start_address <= pc && pc < end_address) {
+        ssize_t len1 = ReadFromOffset(fd, out, out_size,
+                                      strtab->sh_offset + symbol.st_name);
+        if (len1 <= 0 || memchr(out, '\0', out_size) == NULL) {
+          return false;
+        }
+        return true;  // Obtained the symbol name.
+      }
+    }
+    i += num_symbols_in_buf;
+  }
+  return false;
+}
+
+// Get the symbol name of "pc" from the file pointed by "fd".  Process
+// both regular and dynamic symbol tables if necessary.  On success,
+// write the symbol name to "out" and return true.  Otherwise, return
+// false.
+static bool GetSymbolFromObjectFile(const int fd, uint64_t pc,
+                                    char *out, int out_size,
+                                    uint64_t map_start_address) {
+  // Read the ELF header.
+  ElfW(Ehdr) elf_header;
+  if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
+    return false;
+  }
+
+  uint64_t symbol_offset = 0;
+  if (elf_header.e_type == ET_DYN) {  // DSO needs offset adjustment.
+    symbol_offset = map_start_address;
+  }
+
+  ElfW(Shdr) symtab, strtab;
+
+  // Consult a regular symbol table first.
+  if (!GetSectionHeaderByType(fd, elf_header.e_shnum, elf_header.e_shoff,
+                              SHT_SYMTAB, &symtab)) {
+    return false;
+  }
+  if (!ReadFromOffsetExact(fd, &strtab, sizeof(strtab), elf_header.e_shoff +
+                           symtab.sh_link * sizeof(symtab))) {
+    return false;
+  }
+  if (FindSymbol(pc, fd, out, out_size, symbol_offset,
+                 &strtab, &symtab)) {
+    return true;  // Found the symbol in a regular symbol table.
+  }
+
+  // If the symbol is not found, then consult a dynamic symbol table.
+  if (!GetSectionHeaderByType(fd, elf_header.e_shnum, elf_header.e_shoff,
+                              SHT_DYNSYM, &symtab)) {
+    return false;
+  }
+  if (!ReadFromOffsetExact(fd, &strtab, sizeof(strtab), elf_header.e_shoff +
+                           symtab.sh_link * sizeof(symtab))) {
+    return false;
+  }
+  if (FindSymbol(pc, fd, out, out_size, symbol_offset,
+                 &strtab, &symtab)) {
+    return true;  // Found the symbol in a dynamic symbol table.
+  }
+
+  return false;
+}
+
+namespace {
+// Thin wrapper around a file descriptor so that the file descriptor
+// gets closed for sure.
+struct FileDescriptor {
+  const int fd_;
+  explicit FileDescriptor(int fd) : fd_(fd) {}
+  ~FileDescriptor() {
+    if (fd_ >= 0) {
+      NO_INTR(close(fd_));
+    }
+  }
+  int get() { return fd_; }
+
+ private:
+  explicit FileDescriptor(const FileDescriptor&);
+  void operator=(const FileDescriptor&);
+};
+
+// Helper class for reading lines from file.
+//
+// Note: we don't use ProcMapsIterator since the object is big (it has
+// a 5k array member) and uses async-unsafe functions such as sscanf()
+// and snprintf().
+class LineReader {
+ public:
+  explicit LineReader(int fd, char *buf, int buf_len) : fd_(fd),
+    buf_(buf), buf_len_(buf_len), bol_(buf), eol_(buf), eod_(buf) {
+  }
+
+  // Read '\n'-terminated line from file.  On success, modify "bol"
+  // and "eol", then return true.  Otherwise, return false.
+  //
+  // Note: if the last line doesn't end with '\n', the line will be
+  // dropped.  It's an intentional behavior to make the code simple.
+  bool ReadLine(const char **bol, const char **eol) {
+    if (BufferIsEmpty()) {  // First time.
+      const ssize_t num_bytes = ReadPersistent(fd_, buf_, buf_len_);
+      if (num_bytes <= 0) {  // EOF or error.
+        return false;
+      }
+      eod_ = buf_ + num_bytes;
+      bol_ = buf_;
+    } else {
+      bol_ = eol_ + 1;  // Advance to the next line in the buffer.
+      SAFE_ASSERT(bol_ <= eod_);  // "bol_" can point to "eod_".
+      if (!HasCompleteLine()) {
+        const int incomplete_line_length = eod_ - bol_;
+        // Move the trailing incomplete line to the beginning.
+        memmove(buf_, bol_, incomplete_line_length);
+        // Read text from file and append it.
+        char * const append_pos = buf_ + incomplete_line_length;
+        const int capacity_left = buf_len_ - incomplete_line_length;
+        const ssize_t num_bytes = ReadPersistent(fd_, append_pos,
+                                                 capacity_left);
+        if (num_bytes <= 0) {  // EOF or error.
+          return false;
+        }
+        eod_ = append_pos + num_bytes;
+        bol_ = buf_;
+      }
+    }
+    eol_ = FindLineFeed();
+    if (eol_ == NULL) {  // '\n' not found.  Malformed line.
+      return false;
+    }
+    *eol_ = '\0';  // Replace '\n' with '\0'.
+
+    *bol = bol_;
+    *eol = eol_;
+    return true;
+  }
+
+  // Beginning of line.
+  const char *bol() {
+    return bol_;
+  }
+
+  // End of line.
+  const char *eol() {
+    return eol_;
+  }
+
+ private:
+  explicit LineReader(const LineReader&);
+  void operator=(const LineReader&);
+
+  char *FindLineFeed() {
+    return reinterpret_cast<char *>(memchr(bol_, '\n', eod_ - bol_));
+  }
+
+  bool BufferIsEmpty() {
+    return buf_ == eod_;
+  }
+
+  bool HasCompleteLine() {
+    return !BufferIsEmpty() && FindLineFeed() != NULL;
+  }
+
+  const int fd_;
+  char * const buf_;
+  const int buf_len_;
+  char *bol_;
+  char *eol_;
+  const char *eod_;  // End of data in "buf_".
+};
+}  // namespace
+
+// Place the hex number read from "start" into "*hex".  The pointer to
+// the first non-hex character or "end" is returned.
+static char *GetHex(const char *start, const char *end, uint64_t *hex) {
+  *hex = 0;
+  const char *p;
+  for (p = start; p < end; ++p) {
+    int ch = *p;
+    if ((ch >= '0' && ch <= '9') ||
+        (ch >= 'A' && ch <= 'F') || (ch >= 'a' && ch <= 'f')) {
+      *hex = (*hex << 4) | (ch < 'A' ? ch - '0' : (ch & 0xF) + 9);
+    } else {  // Encountered the first non-hex character.
+      break;
+    }
+  }
+  SAFE_ASSERT(p <= end);
+  return const_cast<char *>(p);
+}
+
+// Search for the object file (from /proc/self/maps) that contains
+// the specified pc. If found, open this file and return the file handle,
+// and also set start_address to the start address of where this object
+// file is mapped to in memory. Otherwise, return -1.
+static ATTRIBUTE_NOINLINE int
+OpenObjectFileContainingPcAndGetStartAddress(uint64_t pc,
+                                             uint64_t &start_address) {
+  int object_fd;
+
+  // Open /proc/self/maps.
+  int maps_fd;
+  NO_INTR(maps_fd = open("/proc/self/maps", O_RDONLY));
+  FileDescriptor wrapped_maps_fd(maps_fd);
+  if (wrapped_maps_fd.get() < 0) {
+    return -1;
+  }
+
+  // Iterate over maps and look for the map containing the pc.  Then
+  // look into the symbol tables inside.
+  char buf[1024];  // Big enough for line of sane /proc/self/maps
+  LineReader reader(wrapped_maps_fd.get(), buf, sizeof(buf));
+  while (true) {
+    const char *cursor;
+    const char *eol;
+    if (!reader.ReadLine(&cursor, &eol)) {  // EOF or malformed line.
+      return -1;
+    }
+
+    // Start parsing line in /proc/self/maps.  Here is an example:
+    //
+    // 08048000-0804c000 r-xp 00000000 08:01 2142121    /bin/cat
+    //
+    // We want start address (08048000), end address (0804c000), flags
+    // (r-xp) and file name (/bin/cat).
+
+    // Read start address.
+    cursor = GetHex(cursor, eol, &start_address);
+    if (cursor == eol || *cursor != '-') {
+      return -1;  // Malformed line.
+    }
+    ++cursor;  // Skip '-'.
+
+    // Read end address.
+    uint64_t end_address;
+    cursor = GetHex(cursor, eol, &end_address);
+    if (cursor == eol || *cursor != ' ') {
+      return -1;  // Malformed line.
+    }
+    ++cursor;  // Skip ' '.
+
+    // Check start and end addresses.
+    if (!(start_address <= pc && pc < end_address)) {
+      continue;  // We skip this map.  PC isn't in this map.
+    }
+
+    // Read flags.  Skip flags until we encounter a space or eol.
+    const char * const flags_start = cursor;
+    while (cursor < eol && *cursor != ' ') {
+      ++cursor;
+    }
+    // We expect at least four letters for flags (ex. "r-xp").
+    if (cursor == eol || cursor < flags_start + 4) {
+      return -1;  // Malformed line.
+    }
+
+    // Check flags.  We are only interested in "r-x" maps.
+    if (memcmp(flags_start, "r-x", 3) != 0) {  // Not a "r-x" map.
+      continue;  // We skip this map.
+    }
+    ++cursor;  // Skip ' '.
+
+    // Skip to file name.  "cursor" now points to file offset.  We need to
+    // skip at least three spaces for file offset, dev, and inode.
+    int num_spaces = 0;
+    while (cursor < eol) {
+      if (*cursor == ' ') {
+        ++num_spaces;
+      } else if (num_spaces >= 3) {
+        // The first non-space character after  skipping three spaces
+        // is the beginning of the file name.
+        break;
+      }
+      ++cursor;
+    }
+    if (cursor == eol) {
+      return -1;  // Malformed line.
+    }
+
+    // Finally, "cursor" now points to file name of our interest.
+    NO_INTR(object_fd = open(cursor, O_RDONLY));
+    if (object_fd < 0) {
+      return -1;
+    }
+    return object_fd;
+  }
+}
+
+// The implementation of our symbolization routine.  If it
+// successfully finds the symbol containing "pc" and obtains the
+// symbol name, returns true and write the symbol name to "out".
+// Otherwise, returns false. If Callback function is installed via
+// InstallSymbolizeCallback(), the function is also called in this function,
+// and "out" is used as its output.
+// To keep stack consumption low, we would like this function to not
+// get inlined.
+static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
+                                                    int out_size) {
+  uint64_t pc0 = reinterpret_cast<uintptr_t>(pc);
+  uint64_t start_address = 0;
+
+  int object_fd = OpenObjectFileContainingPcAndGetStartAddress(pc0,
+                                                               start_address);
+  if (object_fd == -1) {
+    return false;
+  }
+  FileDescriptor wrapped_object_fd(object_fd);
+  int elf_type = FileGetElfType(wrapped_object_fd.get());
+  if (elf_type == -1) {
+    return false;
+  }
+  if (g_symbolize_callback) {
+    // Run the call back if it's installed.
+    // Note: relocation (and much of the rest of this code) will be
+    // wrong for prelinked shared libraries and PIE executables.
+    uint64 relocation = (elf_type == ET_DYN) ? start_address : 0;
+    int num_bytes_written = g_symbolize_callback(wrapped_object_fd.get(),
+                                                 pc, out, out_size,
+                                                 relocation);
+    if (num_bytes_written > 0) {
+      out += num_bytes_written;
+      out_size -= num_bytes_written;
+    }
+  }
+  if (!GetSymbolFromObjectFile(wrapped_object_fd.get(), pc0,
+                               out, out_size, start_address)) {
+    return false;
+  }
+
+  // Symbolization succeeded.  Now we try to demangle the symbol.
+  DemangleInplace(out, out_size);
+  return true;
+}
+
+_END_GOOGLE_NAMESPACE_
+
+#elif defined(OS_MACOSX) && defined(HAVE_DLADDR)
+
+#include <dlfcn.h>
+#include <string.h>
+
+_START_GOOGLE_NAMESPACE_
+
+static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
+                                                    int out_size) {
+  Dl_info info;
+  if (dladdr(pc, &info)) {
+    if (strlen(info.dli_sname) < out_size) {
+      strcpy(out, info.dli_sname);
+      // Symbolization succeeded.  Now we try to demangle the symbol.
+      DemangleInplace(out, out_size);
+      return true;
+    }
+  }
+  return false;
+}
+
+_END_GOOGLE_NAMESPACE_
+
+#else
+# error BUG: HAVE_SYMBOLIZE was wrongly set
+#endif
+
+_START_GOOGLE_NAMESPACE_
+
+bool Symbolize(void *pc, char *out, int out_size) {
+  SAFE_ASSERT(out_size >= 0);
+  return SymbolizeAndDemangle(pc, out, out_size);
+}
+
+_END_GOOGLE_NAMESPACE_
+
+#else  /* HAVE_SYMBOLIZE */
+
+#include <assert.h>
+
+#include "config.h"
+
+_START_GOOGLE_NAMESPACE_
+
+// TODO: Support other environments.
+bool Symbolize(void *pc, char *out, int out_size) {
+  assert(0);
+  return false;
+}
+
+_END_GOOGLE_NAMESPACE_
+
+#endif