[Bug c/31907] New: isnan builtin doesn't work

[Bug c/31907] New: isnan builtin doesn't work

[akr at m17n dot org]

isnan(0.0/0.0) returns false.
It returns true if -fno-builtin.

KUROBOX-PRO(22:33:53)% cat tst.c 
extern void abort(void);
extern int isnan(double v);

int main()
{
  if (!isnan(0.0/0.0))
    abort();
  return 0;
}
KUROBOX-PRO(22:34:02)% ~/src/gcc/bin/gcc -v tst.c          
Using built-in specs.
Target: armv5tejl-unknown-linux-gnu
Configured with: ../gcc-4.1.2/configure --prefix=/home/akr/src/gcc
--enable-languages=c
Thread model: posix
gcc version 4.1.2
 /home/akr/src/gcc/libexec/gcc/armv5tejl-unknown-linux-gnu/4.1.2/cc1 -quiet -v
tst.c -quiet -dumpbase tst.c -auxbase tst -version -o /tmp/ccBo6vhT.s
ignoring nonexistent directory
"/home/akr/src/gcc/lib/gcc/armv5tejl-unknown-linux-gnu/4.1.2/../../../../armv5tejl-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /home/akr/src/gcc/include
 /home/akr/src/gcc/lib/gcc/armv5tejl-unknown-linux-gnu/4.1.2/include
 /usr/include
End of search list.
GNU C version 4.1.2 (armv5tejl-unknown-linux-gnu)
        compiled by GNU C version 4.1.2.
GGC heuristics: --param ggc-min-expand=38 --param ggc-min-heapsize=15791
Compiler executable checksum: 332d6ae8f800e7865f327fc747ec5bd6
 as -o /tmp/cc8FEJCO.o /tmp/ccBo6vhT.s
 /home/akr/src/gcc/libexec/gcc/armv5tejl-unknown-linux-gnu/4.1.2/collect2
--eh-frame-hdr -dynamic-linker /lib/ld-linux.so.2 -X -m armelf_linux -p
/usr/lib/crt1.o /usr/lib/crti.o
/home/akr/src/gcc/lib/gcc/armv5tejl-unknown-linux-gnu/4.1.2/crtbegin.o
-L/home/akr/src/gcc/lib/gcc/armv5tejl-unknown-linux-gnu/4.1.2
-L/home/akr/src/gcc/lib/gcc/armv5tejl-unknown-linux-gnu/4.1.2/../../..
/tmp/cc8FEJCO.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed
-lgcc_s --no-as-needed
/home/akr/src/gcc/lib/gcc/armv5tejl-unknown-linux-gnu/4.1.2/crtend.o
/usr/lib/crtn.o
KUROBOX-PRO(22:34:09)% ./a.out 
zsh: abort      ./a.out

It doesn't abort if -fno-builtin is used.

KUROBOX-PRO(22:34:18)% ~/src/gcc/bin/gcc -fno-builtin tst.c
KUROBOX-PRO(22:34:22)% ./a.out


-- 
           Summary: isnan builtin doesn't work
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: akr at m17n dot org
 GCC build triplet: armv5tejl-unknown-linux-gnu
  GCC host triplet: armv5tejl-unknown-linux-gnu
GCC target triplet: armv5tejl-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31907

[Bug target/31907] isnan builtin doesn't work

[akr at m17n dot org]

------- Comment #1 from akr at m17n dot org  2007-11-23 07:52 -------
(In reply to comment #0)
> isnan(0.0/0.0) returns false.
> It returns true if -fno-builtin.

I found it is a problem of FPU emulation in Linux kernel.

The problem is caused by FASTFPE.
NWFPE doesn't have the problem.


-- 

akr at m17n dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31907