[Bug c/24971] New: missing prototype causes strange effect at a distance with float.

2005-11-21 Thread hansen at cmu dot edu 
(972) uname -a
FreeBSD gadoid.ices.cmu.edu 5.2.1-RELEASE FreeBSD 5.2.1-RELEASE #0: Mon Feb 23
20:45:55 GMT 2004 [EMAIL PROTECTED]:/usr/obj/usr/src/sys/GENERIC 
i386
(973) cat a.c
#include 
#include 

int main(int argc,char *argv[])
{
  float n = 40;
  int i;

  for (i = 0;i < 10;i++)
foo();

  printf("%g\n",n + 2.0);
  return 0;
}

float foo()
{
  return 1.0;
}
(974) gcc a.c -o a
a.c:17: warning: type mismatch with previous implicit declaration
a.c:10: warning: previous implicit declaration of `foo'
a.c:17: warning: `foo' was previously implicitly declared to return `int'
(975) ./a
nan
(976) 

The above program is missing a prototype for the "foo" function.  This
correctly causes a warning, but the missing prototype causes problems for
completely unrelated code.  In the above example, the foo() function is called
10 times, then an unrelated floating point operation is peformed which
incorrectly results in a "nan".  Note that if the number of loop iterations is
reduced to 6 or fewer times, the program will print the correct result.


-- 
   Summary: missing prototype causes strange effect at a distance
with float.
   Product: gcc
   Version: 3.3.3
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hansen at cmu dot edu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24971

[Bug c/24972] New: missing prototype causes strange effect at a distance with float.

2005-11-21 Thread hansen at cmu dot edu 
(972) uname -a
FreeBSD gadoid.ices.cmu.edu 5.2.1-RELEASE FreeBSD 5.2.1-RELEASE #0: Mon Feb 23
20:45:55 GMT 2004 [EMAIL PROTECTED]:/usr/obj/usr/src/sys/GENERIC 
i386
(973) cat a.c
#include 
#include 

int main(int argc,char *argv[])
{
  float n = 40;
  int i;

  for (i = 0;i < 10;i++)
foo();

  printf("%g\n",n + 2.0);
  return 0;
}

float foo()
{
  return 1.0;
}
(974) gcc a.c -o a
a.c:17: warning: type mismatch with previous implicit declaration
a.c:10: warning: previous implicit declaration of `foo'
a.c:17: warning: `foo' was previously implicitly declared to return `int'
(975) ./a
nan
(976) 

The above program is missing a prototype for the "foo" function.  This
correctly causes a warning, but the missing prototype causes problems for
completely unrelated code.  In the above example, the foo() function is called
10 times, then an unrelated floating point operation is peformed which
incorrectly results in a "nan".  Note that if the number of loop iterations is
reduced to 6 or fewer times, the program will print the correct result.


-- 
   Summary: missing prototype causes strange effect at a distance
with float.
   Product: gcc
   Version: 3.3.3
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hansen at cmu dot edu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24972

[Bug c/24973] New: missing prototype causes strange effect at a distance with float.

2005-11-21 Thread hansen at cmu dot edu 
(972) uname -a
FreeBSD gadoid.ices.cmu.edu 5.2.1-RELEASE FreeBSD 5.2.1-RELEASE #0: Mon Feb 23
20:45:55 GMT 2004 [EMAIL PROTECTED]:/usr/obj/usr/src/sys/GENERIC 
i386
(973) cat a.c
#include 
#include 

int main(int argc,char *argv[])
{
  float n = 40;
  int i;

  for (i = 0;i < 10;i++)
foo();

  printf("%g\n",n + 2.0);
  return 0;
}

float foo()
{
  return 1.0;
}
(974) gcc a.c -o a
a.c:17: warning: type mismatch with previous implicit declaration
a.c:10: warning: previous implicit declaration of `foo'
a.c:17: warning: `foo' was previously implicitly declared to return `int'
(975) ./a
nan
(976) 

The above program is missing a prototype for the "foo" function.  This
correctly causes a warning, but the missing prototype causes problems for
completely unrelated code.  In the above example, the foo() function is called
10 times, then an unrelated floating point operation is peformed which
incorrectly results in a "nan".  Note that if the number of loop iterations is
reduced to 6 or fewer times, the program will print the correct result.


-- 
   Summary: missing prototype causes strange effect at a distance
with float.
   Product: gcc
   Version: 3.3.3
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hansen at cmu dot edu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24973

[Bug c/24971] missing prototype causes strange effect at a distance with float.

2005-11-21 Thread hansen at cmu dot edu 


--- Comment #5 from hansen at cmu dot edu  2005-11-21 15:28 ---
(In reply to comment #2)
> Note the error is:
> t.c:17: error: conflicting types for ‘foo’
> t.c:10: error: previous implicit declaration of ‘foo’ was here
> 

I only get warnings in 3.3.0.  Even with warnings, I still do not think that
there should be an effect in code unrelated to the warning.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24971