* lib/free.c (rpl_free): Preserve errno. Check for null only if
CANNOT_FREE_NULL is defined, as an optimization for POSIX 2008
platforms that do not preserve errno.
* m4/free.m4 (gl_FUNC_FREE): Check whether free preserves errno.
Also, define CANNOT_FREE_NULL if free cannot free NULL.
* modules/free (configure.ac): Also replace 'free' if
it does not preserve errno.
---
ChangeLog | 9 +++++++++
lib/free.c | 12 ++++++++++--
m4/free.m4 | 35 ++++++++++++++++++++++++++++++++++-
modules/free | 12 ++++++------
4 files changed, 59 insertions(+), 9 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 445e2c074..e97d82aa6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,14 @@
2020-12-17 Paul Eggert <egg...@cs.ucla.edu>
+ free: preserve errno
+ * lib/free.c (rpl_free): Preserve errno. Check for null only if
+ CANNOT_FREE_NULL is defined, as an optimization for POSIX 2008
+ platforms that do not preserve errno.
+ * m4/free.m4 (gl_FUNC_FREE): Check whether free preserves errno.
+ Also, define CANNOT_FREE_NULL if free cannot free NULL.
+ * modules/free (configure.ac): Also replace 'free' if
+ it does not preserve errno.
+
idx: simplify IDX_MAX, remove IDX_WIDTH
* lib/idx.h (IDX_MAX): Simplify by removing obsolete reference
to UNSIGNED_IDX_T.
diff --git a/lib/free.c b/lib/free.c
index 50a300ffa..843ce4816 100644
--- a/lib/free.c
+++ b/lib/free.c
@@ -22,9 +22,17 @@
#include <stdlib.h>
+#include <errno.h>
+
void
rpl_free (void *p)
{
- if (p)
- free (p);
+#ifdef CANNOT_FREE_NULL
+ if (!p)
+ return;
+#endif
+
+ int err = errno;
+ free (p);
+ errno = err;
}
diff --git a/m4/free.m4 b/m4/free.m4
index a62214cd1..62daa8ecc 100644
--- a/m4/free.m4
+++ b/m4/free.m4
@@ -35,10 +35,43 @@ AC_DEFUN([gl_FUNC_FREE],
esac
])
+ dnl In the next release of POSIX, free must preserve errno.
+ dnl https://www.austingroupbugs.net/view.php?id=385
+ dnl https://sourceware.org/bugzilla/show_bug.cgi?id=17924
+ dnl For now, assume implementations other than glibc do not preserve errno
+ dnl unless they set _POSIX_VERSION to the next release number,
+ dnl whatever that happens to be.
+ AC_CACHE_CHECK([whether free is known to preserve errno],
+ [gl_cv_func_free_preserves_errno],
+ [case $host_os in
+ *-gnu* | gnu*)
+ gl_cv_func_free_preserves_errno=yes;;
+ *)
+ AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[#include <unistd.h>
+ ]],
+ [[#if _POSIX_VERSION <= 200809
+ #error "'free' is not known to preserve errno"
+ #endif
+ ]])],
+ [gl_cv_func_free_preserves_errno=yes],
+ [gl_cv_func_free_preserves_errno=no]);;
+ esac
+ ])
+
if test $gl_cv_func_free = no; then
+ AC_DEFINE([CANNOT_FREE_NULL], [1],
+ [Define to 1 if free (NULL) does not work.])
+ fi
+
+ case $gl_cv_func_free,$gl_cv_func_free_preserves_errno in
+ *yes,*yes) ;;
+ *)
AC_DEFINE([free], [rpl_free],
[Define to rpl_free if the replacement function should be used.])
- fi
+ ;;
+ esac
])
# Prerequisites of lib/free.c.
diff --git a/modules/free b/modules/free
index ec91f8889..ea2509821 100644
--- a/modules/free
+++ b/modules/free
@@ -1,8 +1,5 @@
Description:
-Work around incompatibility on older systems where free (NULL) fails.
-
-Notice:
-This module is obsolete.
+Work around systems where free sets errno or free (NULL) fails.
Files:
lib/free.c
@@ -12,10 +9,13 @@ Depends-on:
configure.ac:
gl_FUNC_FREE
-if test $gl_cv_func_free = no; then
+case $gl_cv_func_free,$gl_cv_func_free_errno in
+ *yes,*yes) ;;
+ *)
AC_LIBOBJ([free])
gl_PREREQ_FREE
-fi
+ ;;
+esac
Makefile.am:
--
2.27.0
