Prevent segfault if file cannot be opened when --ll_prof is used.

src/platform-openbsd.cc

 // Copyright 2012 the V8 project authors. 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
@@ skipping 326 matching lines @@
   // Support for ll_prof.py.
   //
   // The Linux profiler built into the kernel logs all mmap's with
   // PROT_EXEC so that analysis tools can properly attribute ticks. We
   // do a mmap with a name known by ll_prof.py and immediately munmap
   // it. This injects a GC marker into the stream of events generated
   // by the kernel and allows us to synchronize V8 code log and the
   // kernel log.
   int size = sysconf(_SC_PAGESIZE);
   FILE* f = fopen(FLAG_gc_fake_mmap, "w+");
+  if (f == NULL) {
+    OS::PrintError("Failed to open %s\n", FLAG_gc_fake_mmap);
+    OS::Abort();
+  }
   void* addr = mmap(NULL, size, PROT_READ | PROT_EXEC, MAP_PRIVATE,
                     fileno(f), 0);
   ASSERT(addr != MAP_FAILED);
   OS::Free(addr, size);
   fclose(f);
 }
 
 
 int OS::StackWalk(Vector<OS::StackFrame> frames) {
   // backtrace is a glibc extension.
@@ skipping 378 matching lines @@
   limit_mutex = CreateMutex();
 }
 
 
 void OS::TearDown() {
   delete limit_mutex;
 }
 
 
 } }  // namespace v8::internal