-/* Perform a binary search to find which option the command-line INPUT
- matches. Returns its index in the option array, and N_OPTS
- (cl_options_count) on failure.
-
- This routine is quite subtle. A normal binary search is not good
- enough because some options can be suffixed with an argument, and
- multiple sub-matches can occur, e.g. input of "-pedantic" matching
- the initial substring of "-pedantic-errors".
-
- A more complicated example is -gstabs. It should match "-g" with
- an argument of "stabs". Suppose, however, that the number and list
- of switches are such that the binary search tests "-gen-decls"
- before having tested "-g". This doesn't match, and as "-gen-decls"
- is less than "-gstabs", it will become the lower bound of the
- binary search range, and "-g" will never be seen. To resolve this
- issue, opts.sh makes "-gen-decls" point, via the back_chain member,
- to "-g" so that failed searches that end between "-gen-decls" and
- the lexicographically subsequent switch know to go back and see if
- "-g" causes a match (which it does in this example).
-
- This search is done in such a way that the longest match for the
- front end in question wins. If there is no match for the current
- front end, the longest match for a different front end is returned
- (or N_OPTS if none) and the caller emits an error message. */
-static size_t
-find_opt (const char *input, int lang_mask)
-{
- size_t mn, mx, md, opt_len;
- size_t match_wrong_lang;
- int comp;
-
- mn = 0;
- mx = cl_options_count;
-
- /* Find mn such this lexicographical inequality holds:
- cl_options[mn] <= input < cl_options[mn + 1]. */
- while (mx - mn > 1)
- {
- md = (mn + mx) / 2;
- opt_len = cl_options[md].opt_len;
- comp = strncmp (input, cl_options[md].opt_text + 1, opt_len);
-
- if (comp < 0)
- mx = md;
- else
- mn = md;
- }
-
- /* This is the switch that is the best match but for a different
- front end, or cl_options_count if there is no match at all. */
- match_wrong_lang = cl_options_count;
-
- /* Backtrace the chain of possible matches, returning the longest
- one, if any, that fits best. With current GCC switches, this
- loop executes at most twice. */
- do
- {
- const struct cl_option *opt = &cl_options[mn];
-
- /* Is this switch a prefix of the input? */
- if (!strncmp (input, opt->opt_text + 1, opt->opt_len))
- {
- /* If language is OK, and the match is exact or the switch
- takes a joined argument, return it. */
- if ((opt->flags & lang_mask)
- && (input[opt->opt_len] == '\0' || (opt->flags & CL_JOINED)))
- return mn;
-
- /* If we haven't remembered a prior match, remember this
- one. Any prior match is necessarily better. */
- if (match_wrong_lang == cl_options_count)
- match_wrong_lang = mn;
- }
-
- /* Try the next possibility. This is cl_options_count if there
- are no more. */
- mn = opt->back_chain;
- }
- while (mn != cl_options_count);
-
- /* Return the best wrong match, or cl_options_count if none. */
- return match_wrong_lang;
-}
-
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