prefix_filename(): safely handle the case where pfx_len=0

diff --git a/xdiff/xmacros.h b/xdiff/xmacros.h
index 8ef232cfad12d706aaafe705bf16c546f3597182..165a895a93e04b33ca7c8f3839ee85e0eccb4a07 100644 (file)
--- a/xdiff/xmacros.h
+++ b/xdiff/xmacros.h
@@ -30,6 +30,7 @@
 #define XDL_MAX(a, b) ((a) > (b) ? (a): (b))
 #define XDL_ABS(v) ((v) >= 0 ? (v): -(v))
 #define XDL_ISDIGIT(c) ((c) >= '0' && (c) <= '9')
+#define XDL_ISSPACE(c) (isspace((unsigned char)(c)))
 #define XDL_ADDBITS(v,b)       ((v) + ((v) >> (b)))
 #define XDL_MASKBITS(b)                ((1UL << (b)) - 1)
 #define XDL_HASHLONG(v,b)      (XDL_ADDBITS((unsigned long)(v), b) & XDL_MASKBITS(b))