[openssh-commits] [openssh] 04/07: Handle calloc(0, x) where different from malloc.

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dtucker pushed a commit to branch master
in repository openssh.

commit e9dede06e5bc582a4aeb5b1cd5a7a640d7de3609
Author: Darren Tucker <dtucker at dtucker.net>
Date:   Sun Feb 25 10:20:31 2018 +1100

    Handle calloc(0,x) where different from malloc.
    
    Configure assumes that if malloc(0) returns null then calloc(0,n)
    also does.  On some old platforms (SunOS4) malloc behaves as expected
    (as determined by AC_FUNC_MALLOC) but calloc doesn't.  Test for this
    at configure time and activate the replacement function if found, plus
    handle this case in rpl_calloc.
---
 configure.ac                | 19 +++++++++++++++++--
 openbsd-compat/bsd-malloc.c |  2 ++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 03cc3f86..605844ba 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1337,8 +1337,23 @@ AC_FUNC_STRFTIME
 AC_FUNC_MALLOC
 AC_FUNC_REALLOC
 # autoconf doesn't have AC_FUNC_CALLOC so fake it if malloc returns NULL;
-if test "x$ac_cv_func_malloc_0_nonnull" != "xyes"; then
-	AC_DEFINE(HAVE_CALLOC, 0, [calloc(x, 0) returns NULL])
+AC_MSG_CHECKING([if calloc(0, N) returns non-null])
+AC_RUN_IFELSE(
+	[AC_LANG_PROGRAM(
+		[[ #include <stdlib.h> ]],
+		[[ void *p = calloc(0, 1); exit(p == NULL); ]]
+	)],
+	[ func_calloc_0_nonnull=yes ],
+	[ func_calloc_0_nonnull=no ],
+	[ AC_MSG_WARN([cross compiling: assuming same as malloc])
+	  func_calloc_0_nonnull="$ac_cv_func_malloc_0_nonnull"]
+)
+AC_MSG_RESULT([$func_calloc_0_nonnull])
+
+if test "x$func_calloc_0_nonnull" == "xyes"; then
+	AC_DEFINE(HAVE_CALLOC, 1, [calloc(0, x) returns non-null])
+else
+	AC_DEFINE(HAVE_CALLOC, 0, [calloc(0, x) returns NULL])
 	AC_DEFINE(calloc, rpl_calloc,
 	    [Define to rpl_calloc if the replacement function should be used.])
 fi
diff --git a/openbsd-compat/bsd-malloc.c b/openbsd-compat/bsd-malloc.c
index 6402ab58..482facdc 100644
--- a/openbsd-compat/bsd-malloc.c
+++ b/openbsd-compat/bsd-malloc.c
@@ -50,6 +50,8 @@ rpl_realloc(void *ptr, size_t size)
 {
 	if (size == 0)
 		size = 1;
+	if (ptr == 0)
+		return malloc(size);
 	return realloc(ptr, size);
 }
 #endif

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