[Bug demangler/80513] demangler walks past trailing nul in mangled name in a bunch of cases

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80513

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
For the first problem this should be sufficient:

--- a/libiberty/cplus-dem.c
+++ b/libiberty/cplus-dem.c
@@ -3173,6 +3173,8 @@ gnu_special (struct work_stuff *work, const char
**mangled, string *declp)
       delta = consume_count (mangled);
       if (delta == -1)
        success = 0;
+      else if (*mangled != '_')
+        success = 0;
       else
        {
          char *method = internal_cplus_demangle (work, ++*mangled);