[NOT TO COMMIT!] Merge Chromium-specific changes in tcmalloc thru. the original gperftools r136.

third_party/tcmalloc/chromium/src/base/sysinfo.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
@@ skipping 169 matching lines @@
 // gcc -- if you do a setenv() in a shared libarary in a global
 // constructor, the environment setting is lost by the time main() is
 // called.  The only safe thing we can do in such a situation is to
 // modify the existing envvar.  So we do a hack: in the parent, we set
 // the high bit of the 1st char of CPUPROFILE.  In the child, we
 // notice the high bit is set and append the pid().  This works
 // assuming cpuprofile filenames don't normally have the high bit set
 // in their first character!  If that assumption is violated, we'll
 // still get a profile, but one with an unexpected name.
 // TODO(csilvers): set an envvar instead when we can do it reliably.
+//
+// In Chromium this hack is intentionally disabled, because the path is not
+// re-initialized upon fork.
 bool GetUniquePathFromEnv(const char* env_name, char* path) {
   char* envval = getenv(env_name);
   if (envval == NULL || *envval == '\0')
     return false;
   if (envval[0] & 128) {                  // high bit is set
     snprintf(path, PATH_MAX, "%c%s_%u",   // add pid and clear high bit
              envval[0] & 127, envval+1, (unsigned int)(getpid()));
   } else {
     snprintf(path, PATH_MAX, "%s", envval);
+#if 0
     envval[0] |= 128;                     // set high bit for kids to see
+#endif
   }
   return true;
 }
 
 // ----------------------------------------------------------------------
 // CyclesPerSecond()
 // NumCPUs()
 //    It's important this not call malloc! -- they may be called at
 //    global-construct time, before we've set up all our proper malloc
 //    hooks and such.
@@ skipping 766 matching lines @@
   ProcMapsIterator::Buffer linebuf;
   while (it.Next(&start, &end, &flags, &offset, &inode, &filename)) {
     int written = it.FormatLine(linebuf.buf_, sizeof(linebuf.buf_),
                                 start, end, flags, offset, inode, filename,
                                 0);
     RawWrite(fd, linebuf.buf_, written);
   }
 }
 
 }  // namespace tcmalloc