2017-05-19 Paul Eggert <eggert@cs.ucla.edu>
+ argp: fix shift bug
+ * lib/argp-parse.c (parser_parse_opt): Rework to avoid undefined
+ behavior on shift overflow, caught by gcc -fsanitize=undefined.
+
argp: fix pointer-subtraction bug
* lib/argp-help.c (hol_append): Don’t subtract pointers to
different arrays, as this can run afoul of -fcheck-pointer-bounds.
}
}
else
- /* A long option. We use shifts instead of masking for extracting
- the user value in order to preserve the sign. */
- err =
- group_parse (&parser->groups[group_key - 1], &parser->state,
- (opt << GROUP_BITS) >> GROUP_BITS,
- parser->opt_data.optarg);
+ /* A long option. Preserve the sign in the user key, without
+ invoking undefined behavior. Assume two's complement. */
+ {
+ unsigned uopt = opt;
+ unsigned ushifted_user_key = uopt << GROUP_BITS;
+ int shifted_user_key = ushifted_user_key;
+ int user_key;
+ if (-1 >> 1 == -1)
+ user_key = shifted_user_key >> GROUP_BITS;
+ else
+ user_key = ((ushifted_user_key >> GROUP_BITS)
+ - (shifted_user_key < 0 ? 1 << USER_BITS : 0));
+ err =
+ group_parse (&parser->groups[group_key - 1], &parser->state,
+ user_key, parser->opt_data.optarg);
+ }
if (err == EBADKEY)
/* At least currently, an option not recognized is an error in the