definition of NULL

[Eric Blake]

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Hash: SHA1

Any objections to this patch?  I know that Solaris 10 still uses the
following, which meets C99 and POSIX 2001 but is non-compliant with POSIX
2008:

#ifndef NULL
#if defined(_LP64)
#define NULL    0L
#else
#define NULL    0
#endif
#endif

But I can't think of any valid C construct that can distinguish between an
integral '0' and '((void*)0)' without causing compilation errors.  And
since most modern machines use all 0 bits as the null pointer, passing a
correctly sized integral constant through varags (as in Solaris) is
indistinguishable from passing (void*) cast.  About the only other thing I
can think of where a missing cast makes a difference is places where the
gcc __attribute__((sentinel)) takes effect (it warns if the cast is
missing, even if the integral constant is the correct size), but
installing gcc also installs a fixincludes for NULL for this very reason.
 Thus, even though Solaris cc still sees a non-POSIX definition of NULL,
gcc on Solaris sees ((void*)0) and the sentinel warning does not trigger
for this code:

execlp ("foo", "foo", NULL);

But if anyone can think of any other test we can use to ensure that NULL
can always be safely used without extra casts as an argument to a varargs
function, I'm all ears.  If nothing else, this patch will help us sniff
out if there are any platforms in the wild that define NULL to the wrong
size integral 0.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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>From e1acffdc5d7765b74fec126287b7f4c9de2c7023 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Fri, 26 Jun 2009 08:00:28 -0600
Subject: [PATCH] tests: add test for bogus NULL definition

* tests/test-stdio.c: Ensure POSIX 2008 requirement on NULL.
* tests/test-stdlib.c: Likewise.
* tests/test-string.c: Likewise.
* tests/test-locale.c: Likewise.
* tests/test-unistd.c: Likewise.
* modules/stdio-tests (Depends-on): Add verify.
* modules/stdlib-tests (Depends-on): Likewise.
* modules/string-tests (Depends-on): Likewise.
* modules/locale-tests (Depends-on): Likewise.
* modules/unistd-tests (Depends-on): Likewise.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog            |   14 ++++++++++++++
 modules/locale-tests |    1 +
 modules/stdio-tests  |    1 +
 modules/stdlib-tests |    1 +
 modules/string-tests |    1 +
 modules/unistd-tests |    1 +
 tests/test-locale.c  |    8 +++++++-
 tests/test-stdio.c   |    8 +++++++-
 tests/test-stdlib.c  |    8 +++++++-
 tests/test-string.c  |    8 +++++++-
 tests/test-unistd.c  |    6 ++++++
 11 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 3e5fdb1..573091f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2009-06-26  Eric Blake  <address@hidden>
+
+       tests: add test for bogus NULL definition
+       * tests/test-stdio.c: Ensure POSIX 2008 requirement on NULL.
+       * tests/test-stdlib.c: Likewise.
+       * tests/test-string.c: Likewise.
+       * tests/test-locale.c: Likewise.
+       * tests/test-unistd.c: Likewise.
+       * modules/stdio-tests (Depends-on): Add verify.
+       * modules/stdlib-tests (Depends-on): Likewise.
+       * modules/string-tests (Depends-on): Likewise.
+       * modules/locale-tests (Depends-on): Likewise.
+       * modules/unistd-tests (Depends-on): Likewise.
+
 2009-06-25  Eric Blake  <address@hidden>

        version-etc: fix regression
diff --git a/modules/locale-tests b/modules/locale-tests
index 3a5fa87..19bc373 100644
--- a/modules/locale-tests
+++ b/modules/locale-tests
@@ -2,6 +2,7 @@ Files:
 tests/test-locale.c

 Depends-on:
+verify

 configure.ac:

diff --git a/modules/stdio-tests b/modules/stdio-tests
index cc0f14e..c572bfb 100644
--- a/modules/stdio-tests
+++ b/modules/stdio-tests
@@ -2,6 +2,7 @@ Files:
 tests/test-stdio.c

 Depends-on:
+verify

 configure.ac:

diff --git a/modules/stdlib-tests b/modules/stdlib-tests
index 8a5a78f..3503511 100644
--- a/modules/stdlib-tests
+++ b/modules/stdlib-tests
@@ -2,6 +2,7 @@ Files:
 tests/test-stdlib.c

 Depends-on:
+verify

 configure.ac:

diff --git a/modules/string-tests b/modules/string-tests
index 67d08bb..ab8699a 100644
--- a/modules/string-tests
+++ b/modules/string-tests
@@ -2,6 +2,7 @@ Files:
 tests/test-string.c

 Depends-on:
+verify

 configure.ac:

diff --git a/modules/unistd-tests b/modules/unistd-tests
index 703d557..7f9d44d 100644
--- a/modules/unistd-tests
+++ b/modules/unistd-tests
@@ -2,6 +2,7 @@ Files:
 tests/test-unistd.c

 Depends-on:
+verify

 configure.ac:

diff --git a/tests/test-locale.c b/tests/test-locale.c
index 39e7de9..625cc43 100644
--- a/tests/test-locale.c
+++ b/tests/test-locale.c
@@ -1,5 +1,5 @@
 /* Test of <locale.h> substitute.
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009 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
@@ -20,6 +20,8 @@

 #include <locale.h>

+#include "verify.h"
+
 int a[] =
   {
     LC_ALL,
@@ -31,6 +33,10 @@ int a[] =
     LC_TIME
   };

+/* Check that NULL can be passed through varargs as a pointer type,
+   per POSIX 2008.  */
+verify (sizeof NULL == sizeof (void *));
+
 int
 main ()
 {
diff --git a/tests/test-stdio.c b/tests/test-stdio.c
index a5efa32..dcfe38d 100644
--- a/tests/test-stdio.c
+++ b/tests/test-stdio.c
@@ -1,5 +1,5 @@
 /* Test of <stdio.h> substitute.
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009 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
@@ -20,9 +20,15 @@

 #include <stdio.h>

+#include "verify.h"
+
 /* Check that the various SEEK_* macros are defined.  */
 int sk[] = { SEEK_CUR, SEEK_END, SEEK_SET };

+/* Check that NULL can be passed through varargs as a pointer type,
+   per POSIX 2008.  */
+verify (sizeof NULL == sizeof (void *));
+
 int
 main ()
 {
diff --git a/tests/test-stdlib.c b/tests/test-stdlib.c
index e103d46..ae46ba1 100644
--- a/tests/test-stdlib.c
+++ b/tests/test-stdlib.c
@@ -1,5 +1,5 @@
 /* Test of <stdlib.h> substitute.
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009 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
@@ -20,8 +20,14 @@

 #include <stdlib.h>

+#include "verify.h"
+
 int exitcode;

+/* Check that NULL can be passed through varargs as a pointer type,
+   per POSIX 2008.  */
+verify (sizeof NULL == sizeof (void *));
+
 int
 main ()
 {
diff --git a/tests/test-string.c b/tests/test-string.c
index 68014f5..fe53cd9 100644
--- a/tests/test-string.c
+++ b/tests/test-string.c
@@ -1,5 +1,5 @@
 /* Test of <string.h> substitute.
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009 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
@@ -20,6 +20,12 @@

 #include <string.h>

+#include "verify.h"
+
+/* Check that NULL can be passed through varargs as a pointer type,
+   per POSIX 2008.  */
+verify (sizeof NULL == sizeof (void *));
+
 int
 main ()
 {
diff --git a/tests/test-unistd.c b/tests/test-unistd.c
index 5fed15c..129367b 100644
--- a/tests/test-unistd.c
+++ b/tests/test-unistd.c
@@ -20,6 +20,12 @@

 #include <unistd.h>

+#include "verify.h"
+
+/* Check that NULL can be passed through varargs as a pointer type,
+   per POSIX 2008.  */
+verify (sizeof NULL == sizeof (void *));
+
 /* Check that the various SEEK_* macros are defined.  */
 int sk[] = { SEEK_CUR, SEEK_END, SEEK_SET };

-- 
1.6.3.3.334.g916e1