Use syscmd, ifelse, and sysval. Mainly as an exercise

[gnulib.git] / m4 / regex.m4

diff --git a/m4/regex.m4 b/m4/regex.m4
index a9c2383..073dac5 100644 (file)
--- a/m4/regex.m4
+++ b/m4/regex.m4
@@ -1,15 +1,23 @@
 #serial 1
 
-dnl From grep.
+dnl Derived from code in GNU grep.
 
 AC_DEFUN(jm_WITH_REGEX,
   [
-    AC_ARG_WITH(included-regex,
-               [  --without-included-regex don't compile regex],
-               jm_with_regex=$withval,
-               jm_with_regex=yes)
-    if test "$jm_with_regex" = yes; then
-      LIBOBJS="$LIBOBJS regex.o"
-    fi
+    dnl Even packages that don't use regex.c can use this macro.
+    dnl Of course, for them it doesn't do anything.
+
+    syscmd([test -f lib/regex.c])
+    ifelse(sysval, 0,
+      [
+       AC_ARG_WITH(included-regex,
+           [  --without-included-regex don't compile regex (use with caution)],
+                   jm_with_regex=$withval,
+                   jm_with_regex=yes)
+       if test "$jm_with_regex" = yes; then
+         LIBOBJS="$LIBOBJS regex.o"
+       fi
+      ],
+    )
   ]
 )