Use ftruncate() instead of fwrite() to extend files....

base/shared_memory_posix.cc

Index: base/shared_memory_posix.cc
===================================================================
--- base/shared_memory_posix.cc	(revision 24242)
+++ base/shared_memory_posix.cc	(working copy)
@@ -194,8 +194,6 @@
   file_closer.reset(fp);  // close when we go out of scope
 
   // Make sure the (new) file is the right size.
-  // According to the man page, "Use of truncate() to extend a file is
-  // not portable."
   if (size && (posix_flags & (O_RDWR | O_CREAT))) {
     // Get current size.
     size_t current_size = 0;

[Mark Mentovai, 2009/08/26 01:22:51]

While you're here, move the declaration down to where it's actually used.

[pink (ping after 24hrs), 2009/08/26 15:16:57]

Done.

@@ -203,24 +201,11 @@
     if (fstat(fileno(fp), &stat) != 0)
       return false;
     current_size = stat.st_size;
-    // Possibly grow.
-    if (current_size < size) {
-      if (fseeko(fp, current_size, SEEK_SET) != 0)
+    if (current_size != size) {
+      if (ftruncate(fileno(fp), size) != 0)
         return false;
-      size_t writesize = size - current_size;
-      scoped_array<char> buf(new char[writesize]);
-      memset(buf.get(), 0, writesize);
-      if (fwrite(buf.get(), 1, writesize, fp) != writesize) {
-          return false;
-      }
-      if (fflush(fp) != 0)
+      if (fseeko(fp, size, SEEK_SET) != 0)
         return false;
-    } else if (current_size > size) {
-      // possibly shrink.
-      if ((ftruncate(fileno(fp), size) != 0) ||
-          (fflush(fp) != 0)) {
-        return false;
-      }
     }
   }