https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82063
--- Comment #2 from jim.wilson at linaro dot org --- On Thu, Aug 31, 2017 at 1:32 PM, manu at gcc dot gnu.org <gcc-bugzi...@gcc.gnu.org> wrote: > This is already possible: > https://gcc.gnu.org/onlinedocs/gccint/Option-properties.html > > LangEnabledBy(language, opt) > LangEnabledBy(language, opt, posarg, negarg) > ... > > See examples in c.opt. I did already look at examples, and read the docs, and step through code in the debugger. Posarg and negarg are integers, which are ignored for options that take a string as an argument. So no, this doesn't work. Note in optc-gen.awk, where the handle_generated_option call is generated, the fourth argument is always NULL. This is "const char *arg" which is the argument for options that take string arguments. The fifth argument, int value, is where the posarg/negarg value gets passed. Also, note, in the file opts-common.c, in the function set_options, in the case CLVC_STRING, it uses only arg, it does not use value. Since the posarg/negarg values end up in value here, they are ignored, and are useless. I would rather ask why the -Walloc-size-larger-than= option is (unsuccessfully) being enabled by -Wall. It seems an odd one to try to enable by default. Another weirdness I just noticed, the docs say that a size suffix is optional, but in the function alloc_max_size in calls.c, if no suffix is specified, it does unit = 0; ... w *= unit; which means the argument always gets ignored unless there is a size suffix. I think that should be unit = 1; instead.
