[Bug c++/97086] New: aix: ceilf and truncf do not preserve the sign bit when output is rounded to 0

[Bug c++/97086] New: aix: ceilf and truncf do not preserve the sign bit when output is rounded to 0

[mfarazma.ext at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97086

            Bug ID: 97086
           Summary: aix: ceilf and truncf do not preserve the sign bit
                    when output is rounded to 0
           Product: gcc
           Version: 8.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mfarazma.ext at gmail dot com
  Target Milestone: ---

Test program:

#include <iostream>
#include <math.h>

int main(){
         float input = -0.1;
         printf("%f\n", ceilf(-0.1));  // -0.000000 , correct
         printf("%f\n", ceilf(input)); // 0.000000  , wrong
  return 0;
}

Compile with:
g++ test.cc
./a.out

"ceilf" does not preserve the sign bit when its input is passed by value and
the output is rounded to 0.

The same happens when using "truncf".

[Bug target/97086] aix: ceilf and truncf do not preserve the sign bit when output is rounded to 0

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97086

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |target

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This might NOT be a GCC issue but rather an issue with the libc that AIX has.

[Bug target/97086] aix: ceilf and truncf do not preserve the sign bit when output is rounded to 0

[mfarazma.ext at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97086

--- Comment #2 from m farazma <mfarazma.ext at gmail dot com> ---
Wanted to point out the same happens when using "nearbyint":
```
#include <iostream>
#include <math.h>

int main(){
 std::cout << nearbyintf(-0) << std::endl;
 return 0;
}
```
expected: -0
actual: 0

https://en.cppreference.com/w/c/numeric/math/nearbyint
Above url clearly mentions "If arg is ±0, it is returned, unmodified".

[Bug target/97086] aix: ceilf and truncf do not preserve the sign bit when output is rounded to 0

[mfarazma.ext at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97086

--- Comment #3 from m farazma <mfarazma.ext at gmail dot com> ---
Sorry the above example needs to be changed to this in order to reproduce the
bug:

```
#include <iostream>
#include <math.h>

int main(){
 float a = -0.0;
 std::cout << nearbyintf(a) << std::endl;
 return 0;
}
```