[Bug c/35649] New: Incorrect printf warning: expect double has float

[Bug c/35649] New: Incorrect printf warning: expect double has float

[6yxwfq202 at sneakemail dot com]

With the -Wformat option The code

void foo( float a )
{
    printf("%f",a);
}

give the warning:
foo.c:3: warning: format '%f' expects type 'double', but argument 2 has type
'float'

I believe this is unnecessary because float is promoted to double in variadic
functions.


-- 
           Summary: Incorrect printf warning: expect double has float
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: trivial
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: 6yxwfq202 at sneakemail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2008-03-20 12:40 -------
Works for me.  Which target?  Obviously you may need a prototype of printf
available for -Wformat to work at all.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[6yxwfq202 at sneakemail dot com]

------- Comment #2 from 6yxwfq202 at sneakemail dot com  2008-03-20 16:04 -------
Target is h8300-elf running on pc-windows or pc-cygwin

printf prototype:
extern int printf( const char * fmt, ...);


-- 

6yxwfq202 at sneakemail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 GCC target triplet|                            |h8300-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[wilson at tuliptree dot org]

------- Comment #3 from wilson at tuliptree dot org  2008-03-22 02:13 -------
Subject: Re:   New: Incorrect printf warning: expect double has
 float

6yxwfq202 at sneakemail dot com wrote:
> foo.c:3: warning: format '%f' expects type 'double', but argument 2 has type
> 'float'
> I believe this is unnecessary because float is promoted to double in variadic
> functions.

Small 8/16 bit microprocessors often don't support all FP types. 
h8300.h has for instance
#define FLOAT_TYPE_SIZE 32
#define DOUBLE_TYPE_SIZE        32
So floats and doubles are the same thing, which is probably confusing 
something in the C front end.  Maybe a type conversion got optimized 
away (folded?) because it was a no-op for instance.  I haven't tried to 
reproduce this.

Jim


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[dj at redhat dot com]

------- Comment #4 from dj at redhat dot com  2010-01-08 20:51 -------
Still present in 4.5 trunk, also fails for rx-elf-gcc with -m32bit-doubles but
not with -m64bit-doubles.


-- 

dj at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dj at redhat dot com
   Last reconfirmed|0000-00-00 00:00:00         |2010-01-08 20:51:02
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[dj at redhat dot com]

------- Comment #5 from dj at redhat dot com  2010-09-22 20:13 -------
Still fails for both h8300-elf and rx-elf, both on 4.5 branch and 4.6 trunk.


-- 

dj at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2010-01-08 20:51:02         |2010-09-22 20:13:19
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[dj at redhat dot com]

------- Comment #6 from dj at redhat dot com  2010-09-22 20:22 -------
Created an attachment (id=21866)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21866&action=view)
possible fix

FYI I've been using this to silence the warning in my local tree...


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[paolo dot carlini at oracle dot com]

------- Comment #7 from paolo dot carlini at oracle dot com  2010-09-22 20:38 -------
I have a deja vu


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[joseph at codesourcery dot com]

------- Comment #8 from joseph at codesourcery dot com  2010-09-22 22:40 -------
Subject: Re:  Incorrect printf warning: expect double has float

On Wed, 22 Sep 2010, dj at redhat dot com wrote:

> ------- Comment #6 from dj at redhat dot com  2010-09-22 20:22 -------
> Created an attachment (id=21866)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21866&action=view)
>  --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21866&action=view)
> possible fix
> 
> FYI I've been using this to silence the warning in my local tree...

That's the wrong fix; instead, change convert_arguments to do the 
conversion from float to double even if they have the same precision.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[manu at gcc dot gnu dot org]

------- Comment #9 from manu at gcc dot gnu dot org  2010-09-23 07:54 -------
Why is this waiting? It only requires a fix.


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu dot org
             Status|WAITING                     |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|2010-09-22 20:13:19         |2010-09-23 07:54:25
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

[Bug c/35649] Incorrect printf warning: expect double has float

[amylaar at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

Jorn Wolfgang Rennecke <amylaar at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |amylaar at gcc dot gnu.org
         Resolution|---                         |FIXED

--- Comment #13 from Jorn Wolfgang Rennecke <amylaar at gcc dot gnu.org> ---
Fixed with this patch:
http://gcc.gnu.org/ml/gcc-cvs/2013-08/msg00613.html
http://gcc.gnu.org/ml/gcc-cvs/2013-08/msg00615.html

[Bug c/35649] Incorrect printf warning: expect double has float

[trevmrgn+bug at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

Trevor Morgan <trevmrgn+bug at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|h8300-elf                   |h8300-elf, rx-elf, avr

--- Comment #12 from Trevor Morgan <trevmrgn+bug at gmail dot com> 2013-04-17 15:22:48 UTC ---
printf( "%f", 2.0D );
will also produce the erroneous warning (tried on rx-elf)

[Bug c/35649] Incorrect printf warning: expect double has float

[sgh at sgh dot dk]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

Søren Holm <sgh at sgh dot dk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sgh at sgh dot dk

--- Comment #11 from Søren Holm <sgh at sgh dot dk> 2011-10-15 21:48:25 UTC ---
Iøm having the same isssue whne compiling with -fshort-double

[Bug c/35649] Incorrect printf warning: expect double has float

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35649

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

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

--- Comment #10 from Andrew Pinski <pinskia at gcc dot gnu.org> 2010-11-08 15:39:05 UTC ---
*** Bug 46372 has been marked as a duplicate of this bug. ***