Re: [bug #65537] Werrors from intprops-internal.h with gcc 8.3.0

[Jeffrey Walton]

On Fri, Mar 29, 2024 at 2:15 PM Martin Dorey <INVALID.NOREPLY@gnu.org> wrote:
>
> URL:
>   <https://savannah.gnu.org/bugs/?65537>
>
>                  Summary: Werrors from intprops-internal.h with gcc 8.3.0
>                    Group: make
>                Submitter: mdorey
>                Submitted: Fri 29 Mar 2024 11:14:56 AM PDT
>                 Severity: 3 - Normal
>               Item Group: Build/Install
>                   Status: None
>                  Privacy: Public
>              Assigned to: None
>              Open/Closed: Open
>          Discussion Lock: Any
>        Component Version: SCM
>         Operating System: POSIX-Based
>            Fixed Release: None
>            Triage Status: None
>
>
>     _______________________________________________________
>
> Follow-up Comments:
>
>
> -------------------------------------------------------
> Date: Fri 29 Mar 2024 11:14:56 AM PDT By: Martin Dorey <mdorey>
> A fresh git clone of Gnu Make fails to build for me on Debian 10/Buster with:
>
> mv -f $depbase.Tpo $depbase.Po
> In file included from lib/intprops.h:21,
>                  from src/arscan.c:379:
> src/arscan.c: In function ‘parse_int’:
> lib/intprops-internal.h:39:59: error: comparison of unsigned expression < 0 is
> always false [-Werror=type-limits]
>  #define _GL_EXPR_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0)
>                                                            ^
> lib/intprops-internal.h:166:42: note: in expansion of macro
> ‘_GL_EXPR_SIGNED’
>      ((!_GL_SIGNED_TYPE_OR_EXPR (*(r)) && _GL_EXPR_SIGNED (a) &&
> _GL_EXPR_SIGNED (b) \
>                                           ^~~~~~~~~~~~~~~
> lib/intprops.h:302:37: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_WRAPV’
>  #define INT_MULTIPLY_WRAPV(a, b, r) _GL_INT_MULTIPLY_WRAPV (a, b, r)
>                                      ^~~~~~~~~~~~~~~~~~~~~~
> src/arscan.c:399:14: note: in expansion of macro ‘INT_MULTIPLY_WRAPV’
>            || INT_MULTIPLY_WRAPV (val, base, &val)
>               ^~~~~~~~~~~~~~~~~~
> lib/intprops-internal.h:372:11: error: comparison of unsigned expression < 0
> is always false [-Werror=type-limits]
>     ? ((a) < 0 \
>            ^
> lib/intprops-internal.h:167:10: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_RANGE_OVERFLOW’
>        && _GL_INT_MULTIPLY_RANGE_OVERFLOW (a, b, 0, (__typeof__ (*(r))) -1))
> \
>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lib/intprops.h:302:37: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_WRAPV’
>  #define INT_MULTIPLY_WRAPV(a, b, r) _GL_INT_MULTIPLY_WRAPV (a, b, r)
>                                      ^~~~~~~~~~~~~~~~~~~~~~
> src/arscan.c:399:14: note: in expansion of macro ‘INT_MULTIPLY_WRAPV’
>            || INT_MULTIPLY_WRAPV (val, base, &val)
>               ^~~~~~~~~~~~~~~~~~
> lib/intprops-internal.h:39:59: error: comparison of unsigned expression < 0 is
> always false [-Werror=type-limits]
>  #define _GL_EXPR_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0)
>                                                            ^
> lib/intprops-internal.h:373:10: note: in expansion of macro
> ‘_GL_EXPR_SIGNED’
>        ? (_GL_EXPR_SIGNED (_GL_INT_CONVERT (tmax, b)) \
>           ^~~~~~~~~~~~~~~
> lib/intprops-internal.h:167:10: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_RANGE_OVERFLOW’
>        && _GL_INT_MULTIPLY_RANGE_OVERFLOW (a, b, 0, (__typeof__ (*(r))) -1))
> \
>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lib/intprops.h:302:37: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_WRAPV’
>  #define INT_MULTIPLY_WRAPV(a, b, r) _GL_INT_MULTIPLY_WRAPV (a, b, r)
>                                      ^~~~~~~~~~~~~~~~~~~~~~
> src/arscan.c:399:14: note: in expansion of macro ‘INT_MULTIPLY_WRAPV’
>            || INT_MULTIPLY_WRAPV (val, base, &val)
>               ^~~~~~~~~~~~~~~~~~
> lib/intprops-internal.h:39:59: error: comparison of unsigned expression < 0 is
> always false [-Werror=type-limits]
>  #define _GL_EXPR_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0)
>                                                            ^
> lib/intprops-internal.h:380:10: note: in expansion of macro
> ‘_GL_EXPR_SIGNED’
>        ? (_GL_EXPR_SIGNED (a) \
>           ^~~~~~~~~~~~~~~
> lib/intprops-internal.h:167:10: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_RANGE_OVERFLOW’
>        && _GL_INT_MULTIPLY_RANGE_OVERFLOW (a, b, 0, (__typeof__ (*(r))) -1))
> \
>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lib/intprops.h:302:37: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_WRAPV’
>  #define INT_MULTIPLY_WRAPV(a, b, r) _GL_INT_MULTIPLY_WRAPV (a, b, r)
>                                      ^~~~~~~~~~~~~~~~~~~~~~
> src/arscan.c:399:14: note: in expansion of macro ‘INT_MULTIPLY_WRAPV’
>            || INT_MULTIPLY_WRAPV (val, base, &val)
>               ^~~~~~~~~~~~~~~~~~
> lib/intprops-internal.h:382:35: error: comparison of integer expressions of
> different signedness: ‘int’ and ‘uintmax_t’ {aka ‘long unsigned
> int’} [-Werror=sign-compare]
>           : 0 < (a) && -1 - (tmin) < (a) - 1) \
>                                    ^
> lib/intprops-internal.h:167:10: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_RANGE_OVERFLOW’
>        && _GL_INT_MULTIPLY_RANGE_OVERFLOW (a, b, 0, (__typeof__ (*(r))) -1))
> \
>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lib/intprops.h:302:37: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_WRAPV’
>  #define INT_MULTIPLY_WRAPV(a, b, r) _GL_INT_MULTIPLY_WRAPV (a, b, r)
>                                      ^~~~~~~~~~~~~~~~~~~~~~
> src/arscan.c:399:14: note: in expansion of macro ‘INT_MULTIPLY_WRAPV’
>            || INT_MULTIPLY_WRAPV (val, base, &val)
>               ^~~~~~~~~~~~~~~~~~
> lib/intprops-internal.h:386:11: error: comparison of unsigned expression < 0
> is always false [-Werror=type-limits]
>     : ((a) < 0 \
>            ^
> lib/intprops-internal.h:167:10: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_RANGE_OVERFLOW’
>        && _GL_INT_MULTIPLY_RANGE_OVERFLOW (a, b, 0, (__typeof__ (*(r))) -1))
> \
>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lib/intprops.h:302:37: note: in expansion of macro
> ‘_GL_INT_MULTIPLY_WRAPV’
>  #define INT_MULTIPLY_WRAPV(a, b, r) _GL_INT_MULTIPLY_WRAPV (a, b, r)
>                                      ^~~~~~~~~~~~~~~~~~~~~~
> src/arscan.c:399:14: note: in expansion of macro ‘INT_MULTIPLY_WRAPV’
>            || INT_MULTIPLY_WRAPV (val, base, &val)
>               ^~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> make[1]: *** [Makefile:896: src/arscan.o] Error 1
> make[1]: Leaving directory '/home/martind/download/make-2024-03-29'
> make: *** [Makefile:982: all-recursive] Error 1
> martind@stormy:~/download/make-2024-03-29$
>
> I'm not seriously suggesting it but, having found some mail from over a decade
> ago at
> https://bug-gnulib.gnu.narkive.com/IJgonyeq/test-intprops-c-many-new-warnings
> suggesting ignoring the warnings here, I unblocked myself with:
>
> --- a/maintMakefile
> +++ b/maintMakefile
> @@ -32,6 +32,7 @@ PERLFLAGS := -w
>  MAKE_CFLAGS := -C -Wall -Wextra -Werror -Wwrite-strings -Wshadow \
>         -Wdeclaration-after-statement -Wbad-function-cast -Wformat-security \
>         -Wtype-limits -Wunused-but-set-parameter -Wlogical-op -Wpointer-arith
> \
> +       -Wno-error=type-limits -Wno-error=sign-compare \
>         -Wignored-qualifiers -Wformat-signedness -Wduplicated-cond
>
>  AM_CFLAGS += $(MAKE_CFLAGS)
>
> I see there's
> https://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commitdiff;h=4d38340a76dbee56036a5fcc0f052ebcff616a59
> upstream, though not in Gnu Make.  I don't understand the macro guard there.
> Why would Paul Eggert want to avoid using the pragma in the half-open region
> between gcc 4.4 and gcc 5, while using it for the half-open region from gcc
> 4.0 to gcc 4.4?  I wondered if it was to do with when support for disabling
> warnings was added, but failed to chase down when that was.  The comment
> mentions a version after 13.2 changing behavior, so I wonder if he intended a
> change from 13.3 on, which could be expressed as 14 <= __GNUC__ + (3 <=
> __GNUC_MINOR__), which is only two characters different from what was
> committed.

If I am not mistaken, the 4d3834 commit uses the wrong pragma:

    +/* Pacify GCC 13.2 in some calls to _GL_EXPR_SIGNED.  */
    +#if defined __GNUC__ && 4 < __GNUC__ + (3 <= __GNUC_MINOR__)
    +# pragma GCC diagnostic ignored "-Wtype-limits"
    +#endif

It should use the tautological-compare warning. Or that's the one
we've been using for ages in C++. Clang had the warning before GCC,
and we used it when building with Clang.

    #pragma GCC diagnostic ignored "-Wtautological-compare"

Jeff