[Bug c/89072] -Wall -Werror should be defaults

[Bug c/89072] -Wall -Werror should be defaults

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |xry111 at gcc dot gnu.org

--- Comment #3 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
In GCC 14 several warnings will be turned to errors by default with C99 or a
newer C standard.  But generally -Werror should *never* be the default. 
Besides the reasons Segher and Rich have already given, the standard also
disallows the compiler from randomly rejecting code just because it "looks
suspicious".

[Bug c/89072] -Wall -Werror should be defaults

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

--- Comment #4 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Xi Ruoyao from comment #3)
> In GCC 14 several warnings will be turned to errors by default with C99 or a
> newer C standard.  But generally -Werror should *never* be the default. 
> Besides the reasons Segher and Rich have already given, the standard also
> disallows the compiler from randomly rejecting code just because it "looks
> suspicious".

Huh?  Where does the standard require that?  The closest to it is 4/8: "An 
implementation shall be accompanied by a document that defines all
implementation-defined and locale-specific characteristics and all
extensions." which essentially *allows* such restrictions.  It just has to
be documented.

Of course a good implementation will not reject valid code without a very
good reason to do that.

[Bug c/89072] -Wall -Werror should be defaults

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

--- Comment #5 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
Note that -Wall -Werror seem to be fine in general when they are used alone,
but this combination can be very problematic when other options are used, such
as -std=c90 -pedantic, and other warnings. So default errors need to be
restricted, e.g. rather with something like -Werror=all. But in any case, there
are currently warnings in -Wall that should not be turned into errors by
default, e.g. those related to code style (such as -Wlogical-not-parentheses)
and heuristics (such as -Wmaybe-uninitialized).

[Bug c/89072] -Wall -Werror should be defaults

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

--- Comment #6 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
BTW, note that some code may be generated (instead of being written by a
human). So having some code style being an error by default would be very bad.

[Bug c/89072] -Wall -Werror should be defaults

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

--- Comment #7 from Segher Boessenkool <segher at gcc dot gnu.org> ---
-Werror always is wrong, for any sane users.  Always.  Not just "in general".

[Bug c/89072] -Wall -Werror should be defaults

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

--- Comment #8 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to Segher Boessenkool from comment #7)
> -Werror always is wrong, for any sane users.  Always.  Not just "in general".

-Werror={something you really understand} may be OK.  A -Werror without = is
always wrong.

[Bug c/89072] -Wall -Werror should be defaults

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |jakub at gcc dot gnu.org

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
It is not always wrong, it is a reasonable choice for some projects during
their development, if they are willing to fix or work around all new warnings,
even if they are false positives.
But enabling any kind of -Werror by default is always wrong.

[Bug c/89072] -Wall -Werror should be defaults

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |mpolacek at gcc dot gnu.org
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #10 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I think we have a strong consensus here.

[Bug c/89072] -Wall -Werror should be defaults

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

--- Comment #11 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #9)
> It is not always wrong, it is a reasonable choice for some projects during
> their development, if they are willing to fix or work around all new
> warnings, even if they are false positives.

Sure.  If people want the pain, they can have it.  But it is never okay to
cause other people to have -Werror -- they may have a different compiler
(version) that no one else has tested with, they may have different warnings
enabled, etc.

> But enabling any kind of -Werror by default is always wrong.

Yup.

[Bug c/89072] -Wall -Werror should be defaults

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

--- Comment #12 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to Segher Boessenkool from comment #11)
> Sure.  If people want the pain, they can have it.  But it is never okay to
> cause other people to have -Werror -- they may have a different compiler
> (version) that no one else has tested with, they may have different warnings
> enabled, etc.

For MPFR automated tests (and sometimes during my usual development too), I use
-Werror in combination with -Wall plus some other useful warnings
(-Wold-style-declaration -Wold-style-definition -Wmissing-parameter-type
-Wmissing-prototypes -Wmissing-declarations -Wmissing-field-initializers
-Wc++-compat -Wwrite-strings -Wcast-function-type -Wcast-align=strict
-Wimplicit-fallthrough), and this is very useful, though this sometimes
triggers GCC bugs. But of course, it's for internal use only. And the use of
-Werror without "=" is valid only because I make sure that no other -W...
options are used.

[Bug c/89072] -Wall -Werror should be defaults

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

--- Comment #13 from Segher Boessenkool <segher at gcc dot gnu.org> ---
I always have -Wmissing-declarations -Wformat=2 , for some reason those aren't
in
-Wall, not even in -W .  Crazy if you ask me :-)

[Bug c/89072] -Wall -Werror should be defaults

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89072

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |egallager at gcc dot gnu.org
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=87656

--- Comment #14 from Eric Gallager <egallager at gcc dot gnu.org> ---
Now we're straying into bug 87656...