2 files changed, 19 insertions, 2 deletions

diff --git a/configure.ac b/configure.ac
index 03cc3f869..605844ba2 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 6402ab588..482facdc9 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