Fix VMS-specific wraparound error in S_mayberelocate.

In trimming the trailing slash from a Unix path spec, we haven't
(since 5.003 or so) been ensuring that we weren't stepping off
the beginning of the string.  No, it's not normal to have '/' as
a library path, but if it happens we shouldn't allow a zero or
negative (actually wraparound since unsigned) value for the path
length.

1 files changed, 1 insertions, 1 deletions

diff --git a/perl.c b/perl.c
index 7652052242..827191520f 100644
--- a/perl.c
+++ b/perl.c
@@ -4529,7 +4529,7 @@ S_mayberelocate(pTHX_ const char *const dir, STRLEN len, U32 flags)
 
 	if ((unix = tounixspec_ts(SvPV(libdir,len),NULL)) != NULL) {
 	    len = strlen(unix);
-	    while (unix[len-1] == '/') len--;  /* Cosmetic */
+	    while (len > 1 && unix[len-1] == '/') len--;  /* Cosmetic */
 	    sv_usepvn(libdir,unix,len);
 	}
 	else