On OpenBSD 6.0 the test t/exotic_names.t fails sometimes. (RT#117072)

Program received signal SIGSEGV, Segmentation fault.
0x00000a9bf44b686a in XS_Sub__Name_subname (cv=Variable "cv" is not available.
) at Name.xs:72
72                      else if (*s && s[-1] == '\'') {

(gdb) print s
$1 = 0xa9c6d507000 "test::SOME_y_STASH::SOME_y_NAME"

With OpenBSD malloc randomisation the storage for nameptr is sometimes
at the beginning of the page.  Then accessing s[-1] with s == nameptr
is fatal.

diff --git a/Name.xs b/Name.xs
index 3484085..9a4d493 100644 (file)
--- a/Name.xs
+++ b/Name.xs
@@ -63,13 +63,13 @@ subname(name, sub)
                croak("Not a subroutine reference");
 
        for (s = nameptr; s <= nameptr + namelen; s++) {
-               if (*s == ':' && s[-1] == ':') {
+               if (s > nameptr && *s == ':' && s[-1] == ':') {
                        end = s - 1;
                        begin = ++s;
                        if (seen_quote)
                                need_subst++;
                }
-               else if (*s && s[-1] == '\'') {
+               else if (s > nameptr && *s != '\0' && s[-1] == '\'') {
                        end = s - 1;
                        begin = s;
                        if (seen_quote++)