Disabling errors but keeping warnings

Mason slash.tmp@free.fr
Wed Apr 26 21:56:00 GMT 2017

+ Jakub, Martin, Joseph

Link to original message:

On 26/04/2017 22:35, Segher Boessenkool wrote:

>>> The manual says:
>>> """
>>> When an unrecognized warning option is requested (e.g.,
>>> @option{-Wunknown-warning}), GCC emits a diagnostic stating
>>> that the option is not recognized.  However, if the @option{-Wno-} form
>>> is used, the behavior is slightly different: no diagnostic is
>>> produced for @option{-Wno-unknown-warning} unless other diagnostics
>>> are being produced.  This allows the use of new @option{-Wno-} options
>>> with old compilers, but if something goes wrong, the compiler
>>> warns that an unrecognized option is present.
>>> """

I've run more tests. My results are below.

$ touch empty.c
$ gcc-4.8 -c -Wall -Werror -Wno-foo       empty.c 
$ gcc-5   -c -Wall -Werror -Wno-foo       empty.c 
$ gcc-6   -c -Wall -Werror -Wno-foo       empty.c 
$ gcc-4.8 -c -Wall -Werror -Wno-error=foo empty.c 
cc1: error: -Werror=foo: no option -Wfoo
$ gcc-5   -c -Wall -Werror -Wno-error=foo empty.c 
cc1: error: -Werror=foo: no option -Wfoo
$ gcc-6   -c -Wall -Werror -Wno-error=foo empty.c 
cc1: error: -Werror=foo: no option -Wfoo

Conclusion: all versions I tested behave the same.

1) *Turning off* an unrecognized option is possible.
2) *Downgrading* an unrecognized option from error to warning
   is not currently possible.

gcc/opts.c:    error_at (loc, "-Werror=%s: no option -%s", arg, new_option);

/* Enable (or disable if VALUE is 0) a warning option ARG (language
   mask LANG_MASK, option handlers HANDLERS) as an error for option
   structures OPTS and OPTS_SET, diagnostic context DC (possibly
   NULL), location LOC.  This is used by -Werror=.  */

static void
enable_warning_as_error (const char *arg, int value, unsigned int lang_mask,
			 const struct cl_option_handlers *handlers,
			 struct gcc_options *opts,
			 struct gcc_options *opts_set,
			 location_t loc, diagnostic_context *dc)

Is it supposed to be possible to downgrade an unrecognized option
from error to warning?

What I would like is being able to pass
-Wall -Werror -Wno-error=misleading-indentation
to any version of gcc.


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