Fix undefined behavior when calling isdigit (#988)

diff --git a/MagickCore/delegate.c b/MagickCore/delegate.c
index ce13fb52af0479bba155c59956e7ffaabcf49275..7ecc62def7ec7ee454534ea0dc33f15e3d3bf949 100644 (file)
--- a/MagickCore/delegate.c
+++ b/MagickCore/delegate.c
@@ -931,7 +931,7 @@ RestoreMSCWarning
   extent=MagickPathExtent;  /* allocated space in string */
   number=MagickFalse;  /* is last char a number? */
   for (q=interpret_text; *p!='\0';
-    number=isdigit(*p) ? MagickTrue : MagickFalse,p++)
+    number=isdigit((int) ((unsigned char) *p)) ? MagickTrue : MagickFalse,p++)
   {
     /*
       Interpret escape characters (e.g. Filename: %M).