simplify posix MappedFile::Init and add useful logs

net/disk_cache/blockfile/mapped_file_posix.cc

Index: net/disk_cache/blockfile/mapped_file_posix.cc
diff --git a/net/disk_cache/blockfile/mapped_file_posix.cc b/net/disk_cache/blockfile/mapped_file_posix.cc
index 966fc72686e7b6e2f33bcc4ac4e824027f81806e..159bb95de820d7c2e2e1d6cfdfb2fc4ce2ff6600 100644
--- a/net/disk_cache/blockfile/mapped_file_posix.cc
+++ b/net/disk_cache/blockfile/mapped_file_posix.cc
@@ -5,6 +5,7 @@
 #include "net/disk_cache/blockfile/mapped_file.h"
 
 #include <errno.h>
+#include <string.h>

[rvargas (doing something else), 2014/07/07 23:30:32]

(and this should not be needed)

[Mostyn Bramley-Moore, 2014/07/08 08:07:19]

Done.

 #include <sys/mman.h>
 
 #include "base/files/file_path.h"
@@ -26,8 +27,9 @@ void* MappedFile::Init(const base::FilePath& name, size_t size) {
                  platform_file(), 0);
   init_ = true;
   view_size_ = size;
-  DCHECK(reinterpret_cast<intptr_t>(buffer_) != -1);
-  if (reinterpret_cast<intptr_t>(buffer_) == -1)
+  DLOG_IF(FATAL, buffer_ == MAP_FAILED) << "Failed to mmap " << name.value()
+                                        << ": " << strerror(errno);

[rvargas (doing something else), 2014/07/07 23:30:32]

nit: use DPLOG_IF instead

[Mostyn Bramley-Moore, 2014/07/08 08:07:19]

I hadn't noticed the P logging macros before- nice.

Done.

+  if (buffer_ == MAP_FAILED)
     buffer_ = 0;
 
   // Make sure we detect hardware failures reading the headers.