[Bug c/65040] New: [5 Regression] gcc-5 -Wformat broken

[Bug c/65040] New: [5 Regression] gcc-5 -Wformat broken

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

            Bug ID: 65040
           Summary: [5 Regression] gcc-5 -Wformat broken
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org

$ cat | gcc-5 -x c - -c -o /dev/null -Wformat=2
#include <stdio.h>

void x(unsigned short arg)
{
        printf("%x\n", arg);
}
^D
gives:
<stdin>: In function ‘x’:
<stdin>:5:16: warning: format ‘%x’ expects argument of type ‘unsigned int’, but
argument 2 has type ‘int’ [-Wformat=]

but we know the range of (int)arg is [0, USHORT_MAX] so the warning isn't
helpful - it is technically true but there is no reason to warn here.
>From gcc-bugs-return-476991-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Feb 12 10:33:58 2015
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Subject: [Bug target/65031] [5 Regression] ICE (segfault) on arm-linux-gnueabihf
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide031

--- Comment #2 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> ---
Appears to work with r220637. Checking if dup of PR65003.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |5.0

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-02-12
                 CC|                            |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Taking.  I think check_format_types needs a small tweak to look thru NOP_EXPRs.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

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

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

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started with r209328.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Marek Polacek from comment #2)
> Taking.  I think check_format_types needs a small tweak to look thru
> NOP_EXPRs.

Well, more like do some lame VR computation and not warn if the signedness
doesn't really matter.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mark at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

Mark Wielaard <mark at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at gcc dot gnu.org

--- Comment #5 from Mark Wielaard <mark at gcc dot gnu.org> ---
Note that this also triggers for code that looks just fine to the user:

#include <stdio.h>
#include <inttypes.h>

int
main (int argc, char **argv)
{
  uint8_t u = 16;
  printf ("u = %02" PRIx8 "\n", u);
  return 0;
}

m.c: In function ‘main’:
m.c:8:11: warning: format ‘%x’ expects argument of type ‘unsigned int’, but
argument 2 has type ‘int’ [-Wformat=]
   printf ("u = %02" PRIx8 "\n", u);
           ^

Which is somewhat surprising since the user explicitly matched the type and
format specifier.

This is caused by the definition of the PRIx format specifiers all mapping back
to "x" in inttypes.h

/* lowercase hexadecimal notation.  */
# define PRIx8          "x"
# define PRIx16         "x"
# define PRIx32         "x"
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Subject: [Bug ipa/65039] [5 Regression] g++ 5 segmentation fault when compiling with -O2 optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide039

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I reproduced this with an out-of-date trunk build, but using today's trunk it
compiles OK, so seems to be fixed.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[fche at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fche at redhat dot com

--- Comment #6 from Frank Ch. Eigler <fche at redhat dot com> ---
Note that printf is a varargs function, and is defined to widen
smaller-than-int parameters to at least int.  unsigned short is
subsumed in int.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Fri Feb 13 07:56:14 2015
New Revision: 220677

URL: https://gcc.gnu.org/viewcvs?rev=220677&root=gcc&view=rev
Log:
    PR c/65040
    * c-format.c (check_format_types): Don't warn about different
    signedness if the original value is in the range of WANTED_TYPE.

    * c-c++-common/pr65040.c: New test.

Added:
    trunk/gcc/testsuite/c-c++-common/pr65040.c
Modified:
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c-format.c
    trunk/gcc/testsuite/ChangeLog

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Should be better now.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[jirislaby at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #9 from Jiri Slaby <jirislaby at gmail dot com> ---
What about this?

#include <stdio.h>

void x(char *ch)
{
        printf("%x\n", ch[10]);
}

It still produces the warning. (I cannot reopen as I am not a reporter.)

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #10 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
That's because on your architecture char is signed by default.  Try adding
"unsigned" or using -funsigned-char and the warning should be gone.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
-funsigned-char is an option that shouldn't be used without serious
consideration.
That said, I think in that case the warning is intentional, you are indeed
passing a signed value to unsigned format.  If you don't care about that, don't
use -Wformat=2 or use -Wno-format-signedness.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[jirislaby at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #12 from Jiri Slaby <jirislaby at gmail dot com> ---
(In reply to Marek Polacek from comment #10)
> That's because on your architecture char is signed by default.  Try adding
> "unsigned" or using -funsigned-char and the warning should be gone.

Ok, I wanted to make sure, that the format string is really wrong here. It
should be %hhx.

Ouch, that will be pain to fix all those 400 bad format strings in grub2, given
they use Werror & WFormat :D.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #13 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Note that this patch had a followup: PR65066.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |---

--- Comment #14 from Richard Biener <rguenth at gcc dot gnu.org> ---
#include <stdio.h>
int main()
{
  printf ("%x%u\n", 4, 4);
}
> gcc-5 -Wall t.c -Wformat=2
t.c: In function 'main':
t.c:4:11: warning: format '%x' expects argument of type 'unsigned int', but
argument 2 has type 'int' [-Wformat=]
   printf ("%x%u\n", 4, 4);
           ^
t.c:4:11: warning: format '%u' expects argument of type 'unsigned int', but
argument 3 has type 'int' [-Wformat=]

that's undesirable as well (the constant fits in an unsigned int).

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #15 from Richard Biener <rguenth at gcc dot gnu.org> ---
I'd also say that warnings for formats that do not have a signed form are
useless,
thus for %o, %x and %X.  But I guess you beg to differ.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #16 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Ok, I can fix the integer constant case as well.

(In reply to Richard Biener from comment #15)
> I'd also say that warnings for formats that do not have a signed form are
> useless,
> thus for %o, %x and %X.  But I guess you beg to differ.

I don't know - it wasn't me who implemented this warning, I'm just doing it
less verbose ;).

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #17 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
IMHO the warning is completely useless, but perhaps some people disagree.

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
And it was just mentioned that the diagnostic should print

 [-Wformat-signedness]

not

 [-Wformat=]

(or both)

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #19 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Fri Feb 27 14:11:53 2015
New Revision: 221061

URL: https://gcc.gnu.org/viewcvs?rev=221061&root=gcc&view=rev
Log:
    PR c/65040
    * doc/invoke.texi: Update to reflect that -Wformat=2 doesn't enable
    -Wformat-signedness anymore.

    * c.opt (Wformat-signedness): Don't enable by -Wformat=2.

    * gcc.dg/pr65066.c: Use -Wformat -Wformat-signedness and not
    -Wformat=2.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c.opt
    trunk/gcc/doc/invoke.texi
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/pr65066.c

[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #20 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Closing.