Tweaks to perf jitdump support

runtime/vm/os_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "vm/os.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 133 matching lines @@
     out_file_ = NULL;
     clock_fd_ = -1;
     clock_id_ = kInvalidClockId;
     code_sequence_ = 0;
     Dart_FileOpenCallback file_open = Isolate::file_open_callback();
     Dart_FileWriteCallback file_write = Isolate::file_write_callback();
     Dart_FileCloseCallback file_close = Isolate::file_close_callback();
     if ((file_open == NULL) || (file_write == NULL) || (file_close == NULL)) {
       return;
     }
-    // The Jitdump code observer writes all jitted code into
-    // /tmp/jit-<pid>.dump, we open the file once on initialization and close
-    // it when the VM is going down.
+    // The Jitdump code observer writes all jitted code into the file
+    // 'perf.jitdump' in the current working directory. We open the file once
+    // on initialization and close it when the VM is going down.
     {
       // Open the file.
-      const char* format = "/tmp/jit-%" Pd ".dump";
-      intptr_t pid = getpid();
-      intptr_t len = OS::SNPrint(NULL, 0, format, pid);
-      char* filename = new char[len + 1];
-      OS::SNPrint(filename, len + 1, format, pid);
+      const char* filename = "perf.jitdump";
       out_file_ = (*file_open)(filename, true);
       ASSERT(out_file_ != NULL);
       // Write the jit dump header.
       WriteHeader();
     }
     // perf uses an internal clock and because our output is merged with data
     // collected by perf our timestamps must be consistent. Using
     // the posix-clock-module (/dev/trace_clock) as our time source ensures
     // we are consistent with the perf timestamps.
     clock_id_ = kInvalidClockId;
@@ skipping 446 matching lines @@
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)