[PATCHv2 2/4] xalloc-oversized: new module

[Eric Blake]

Due to inline functions, mere inclusion of xalloc.h can result
in a link dependency on xalloc_die() on some platforms.  However,
there are several modules that want to use just xalloc_oversized
in order to short-circuit the potential to call xalloc_die.
Splitting the macro into a new header and module makes this easy.

* modules/xalloc-oversized: New module.
* modules/xalloc (Depends-on): Add it.
* lib/xalloc.h (xalloc_oversized): Move...
* lib/xalloc-oversized.h: ...into new file.

Signed-off-by: Eric Blake <address@hidden>
---

Rather than copy the body and comments for xalloc_oversized
into multiple files, I think this layout works nicer.

 ChangeLog                |    6 ++++++
 lib/xalloc-oversized.h   |   38 ++++++++++++++++++++++++++++++++++++++
 lib/xalloc.h             |   17 +----------------
 modules/xalloc           |    1 +
 modules/xalloc-oversized |   20 ++++++++++++++++++++
 5 files changed, 66 insertions(+), 16 deletions(-)
 create mode 100644 lib/xalloc-oversized.h
 create mode 100644 modules/xalloc-oversized

diff --git a/ChangeLog b/ChangeLog
index 138c169..049f0e0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2011-04-27  Eric Blake  <address@hidden>

+       xalloc-oversized: new module
+       * modules/xalloc-oversized: New module.
+       * modules/xalloc (Depends-on): Add it.
+       * lib/xalloc.h (xalloc_oversized): Move...
+       * lib/xalloc-oversized.h: ...into new file.
+
        utimecmp: drop dependency on xmalloc
        * lib/utimecmp.c (utimecmp): Work even if hash table cache fails
        due to memory pressure.
diff --git a/lib/xalloc-oversized.h b/lib/xalloc-oversized.h
new file mode 100644
index 0000000..ab19bcf
--- /dev/null
+++ b/lib/xalloc-oversized.h
@@ -0,0 +1,38 @@
+/* xalloc-oversized.h -- memory allocation size checking
+
+   Copyright (C) 1990-2000, 2003-2004, 2006-2011 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef XALLOC_OVERSIZED_H_
+# define XALLOC_OVERSIZED_H_
+
+# include <stddef.h>
+
+/* Return 1 if an array of N objects, each of size S, cannot exist due
+   to size arithmetic overflow.  S must be positive and N must be
+   nonnegative.  This is a macro, not an inline function, so that it
+   works correctly even when SIZE_MAX < N.
+
+   By gnulib convention, SIZE_MAX represents overflow in size
+   calculations, so the conservative dividend to use here is
+   SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
+   However, malloc (SIZE_MAX) fails on all known hosts where
+   sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
+   exactly-SIZE_MAX allocations on such hosts; this avoids a test and
+   branch when S is known to be 1.  */
+# define xalloc_oversized(n, s) \
+    ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
+
+#endif /* !XALLOC_OVERSIZED_H_ */
diff --git a/lib/xalloc.h b/lib/xalloc.h
index 86b9b3e..c1bbe7e 100644
--- a/lib/xalloc.h
+++ b/lib/xalloc.h
@@ -20,6 +20,7 @@

 # include <stddef.h>

+# include "xalloc-oversized.h"

 # ifdef __cplusplus
 extern "C" {
@@ -65,22 +66,6 @@ void *xmemdup (void const *p, size_t s)
 char *xstrdup (char const *str)
       _GL_ATTRIBUTE_MALLOC;

-/* Return 1 if an array of N objects, each of size S, cannot exist due
-   to size arithmetic overflow.  S must be positive and N must be
-   nonnegative.  This is a macro, not an inline function, so that it
-   works correctly even when SIZE_MAX < N.
-
-   By gnulib convention, SIZE_MAX represents overflow in size
-   calculations, so the conservative dividend to use here is
-   SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
-   However, malloc (SIZE_MAX) fails on all known hosts where
-   sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
-   exactly-SIZE_MAX allocations on such hosts; this avoids a test and
-   branch when S is known to be 1.  */
-# define xalloc_oversized(n, s) \
-    ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
-
-
 /* In the following macros, T must be an elementary or structure/union or
    typedef'ed type, or a pointer to such a type.  To apply one of the
    following macros to a function pointer or array type, you need to typedef
diff --git a/modules/xalloc b/modules/xalloc
index 43ee942..0edcfc6 100644
--- a/modules/xalloc
+++ b/modules/xalloc
@@ -9,6 +9,7 @@ m4/xalloc.m4
 Depends-on:
 inline
 xalloc-die
+xalloc-oversized

 configure.ac:
 gl_XALLOC
diff --git a/modules/xalloc-oversized b/modules/xalloc-oversized
new file mode 100644
index 0000000..708c621
--- /dev/null
+++ b/modules/xalloc-oversized
@@ -0,0 +1,20 @@
+Description:
+Check for memory allocation overflow.  Also see xalloc.
+
+Files:
+lib/xalloc-oversized.h
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+
+Include:
+"xalloc-oversized.h"
+
+License:
+GPL
+
+Maintainer:
+all
-- 
1.7.4.4