https://src.fedoraproject.org/rpms/libmcrypt/blob/e02fbd614a5b7ba093e9e15ab322e7eb02d64e3b/f/libmcrypt-configure-c99-2.patch

Fix glitches in the readdir and bcopy probes.  They were
just invalid.

diff --git a/configure b/configure
index d0fb8783e147654b..4fe7660a16359171 100755
--- a/configure
+++ b/configure
@@ -6639,7 +6639,7 @@ fi
 done
 
 
-for ac_func in readdir,,
+for ac_func in readdir
 do
 as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
 echo "$as_me:$LINENO: checking for $ac_func" >&5
@@ -6741,7 +6741,7 @@ fi
 done
 
 
-for ac_func in bcopy,,
+for ac_func in bcopy
 do
 as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
 echo "$as_me:$LINENO: checking for $ac_func" >&5
diff --git a/configure.in b/configure.in
index a815778931728ec2..f0c9a0e8f73e1153 100644
--- a/configure.in
+++ b/configure.in
@@ -204,8 +204,8 @@ AC_FUNC_MEMCMP
 AC_FUNC_REALLOC
 
 AC_CHECK_FUNCS([bzero memmove memset mlock readdir_r strchr strdup strrchr])
-AC_CHECK_FUNCS([readdir,,])
-AC_CHECK_FUNCS([bcopy,,])
+AC_CHECK_FUNCS([readdir])
+AC_CHECK_FUNCS([bcopy])
 
 dnl Checks for libraries.
 AC_C_BIGENDIAN