[Bug c/23913] New: float/int binary conversion -- "-O2 -march=i686"

[Bug c/23913] New: float/int binary conversion -- "-O2 -march=i686"

[larschri at pvv dot ntnu dot no]

Full example files are here:
http://www.pvv.ntnu.no/~larschri/cast-bug/

The compiled program fails to do binary conversion between float and int. Both
sizeof(int) and sizeof(float) is 4, so the two floats below should have the same
binary representation after being written/read to/from the integer object.

float f1 = 4.5;
int i =    *((int*)&f1);
float f2 = *((float*)&i);
assert(f1 == f2);

$ gcc --version
gcc (GCC) 4.0.1 20050727 (Red Hat 4.0.1-5)
Copyright (C) 2005 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ gcc -O2 -march=i686 cast-bug.c
$ ./a.out
a.out: cast-bug.c:8: main: Assertion `f1 == f2' failed.
Aborted

-- 
           Summary: float/int binary conversion -- "-O2 -march=i686"
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: larschri at pvv dot ntnu dot no
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23913

[Bug c/23913] float/int binary conversion -- "-O2 -march=i686"

[larschri at pvv dot ntnu dot no]

------- Additional Comments From larschri at pvv dot ntnu dot no  2005-09-16 11:12 -------
Created an attachment (id=9739)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9739&action=view)
.i file that triggers the bug.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23913

[Bug c/23913] float/int binary conversion -- "-O2 -march=i686"

[ebotcazou at gcc dot gnu dot org]

------- Additional Comments From ebotcazou at gcc dot gnu dot org  2005-09-16 11:16 -------
Your code violates ISO C aliasing rules.  See the docs about -fstrict-aliasing.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23913

[Bug c/23913] float/int binary conversion -- "-O2 -march=i686"

[larschri at pvv dot ntnu dot no]

------- Additional Comments From larschri at pvv dot ntnu dot no  2005-09-16 11:34 -------
I see - thanks!

I didn't use the -Wall options when changing from C++ to C. g++ had the same
problem, but didn't give any warnings with -Wall.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23913

[Bug c/23913] float/int binary conversion -- "-O2 -march=i686"

[larschri at pvv dot ntnu dot no]

------- Additional Comments From larschri at pvv dot ntnu dot no  2005-09-16 12:12 -------
I have filed this enhancment ticket: [Bug c++/23915]

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23913

[Bug c/23913] float/int binary conversion -- "-O2 -march=i686"

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-16 14:18 -------
Mark as a dup of bug 21920.

*** This bug has been marked as a duplicate of 21920 ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23913

[Bug c/23913] float/int binary conversion -- "-O2 -march=i686"

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-16 14:18 -------
Reopening to ...

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23913