Re: [pdf-devel] Doubt about pdf_alloc

[jemarch]

Hi Luca.

Sorry for the delay: I just returned from my winter holidays.

   I'm looking at the code (pdf-alloc.c);  a doubt about pdf_alloc
   function. bzr code is

     ...
     pointer = malloc (size);
     if (!pointer && size != 0)
       {
         pointer = NULL;
       }
       ... 

   Control flow enter the block if pointer is already NULL, isn't
   it? If so the block seems (at least to me) to be useless.  Is it
   a placeholder for other things yet to come?

I applied a little patch that makes pdf_alloc to behave like glibc
malloc when 0 bytes are requested.  See it below.

Thanks for reporting this :)

=== modified file 'ChangeLog'
--- ChangeLog   2009-12-22 18:05:56 +0000
+++ ChangeLog   2010-01-06 09:58:45 +0000
@@ -1,3 +1,12 @@
+2010-01-06  Jose E. Marchesi  <jema...@gnu.org>
+
+       * doc/gnupdf.texi (Memory Allocation): Documentation for
+       `pdf_alloc' updated.
+
+       * src/base/pdf-alloc.c (pdf_alloc): Modified to use the same
+       semantics that glibc malloc when asked to allocate 0 bytes.
+       Reported by Luca Braglia.
+
 2009-12-22  Jose E. Marchesi  <jema...@gnu.org>
 
        * src/base/pdf-types.c (pdf_i64_copy): Buggy assignment to

=== modified file 'doc/gnupdf.texi'
--- doc/gnupdf.texi     2009-12-18 13:15:59 +0000
+++ doc/gnupdf.texi     2010-01-06 09:55:50 +0000
@@ -320,7 +320,8 @@
 
 @table @var
 @item size
-The requested number of octects to allocate.
+The requested number of octects to allocate.  If this value is
+...@code{0} then no memory is allocated and @code{NULL} is returned.
 @end table
 
 @item Returns

=== modified file 'src/base/pdf-alloc.c'
--- src/base/pdf-alloc.c        2009-09-02 14:48:25 +0000
+++ src/base/pdf-alloc.c        2010-01-06 09:56:54 +0000
@@ -1,4 +1,4 @@
-/* -*- mode: C -*- Time-stamp: "09/09/02 16:44:43 jemarch"
+/* -*- mode: C -*- Time-stamp: "10/01/06 10:56:54 jemarch"
  *
  *       File:         pdf-alloc.c
  *       Date:         Fri Feb 22 21:05:05 2008
@@ -36,13 +36,13 @@
 inline void *
 pdf_alloc (const pdf_size_t size)
 {
-  void *pointer;
+  void *pointer = NULL;
 
-  pointer = malloc (size);
-  if (!pointer && size != 0)
+  if (size > 0)
     {
-      pointer = NULL;
+      pointer = malloc (size);
     }
+
   return pointer;
 }