Re: other/8974: fabs error with -ansi

[Warren du Plessis <warren at eng dot up dot ac dot za>]

Hi,

If I try to link with "-static -ansi -lm" I get the following error message:
/tmp/cc6IBIGC.o: In function `main':
/tmp/cc6IBIGC.o(.text+0x43): undefined reference to `fabs'
/tmp/cc6IBIGC.o(.text+0x89): undefined reference to `fabs'
/tmp/cc6IBIGC.o(.text+0xca): undefined reference to `fabs'
collect2: ld returned 1 exit status
If I remove the -ansi flag and compile with "-static -lm" everything 
works perfectly as I explained previously.

I tried compiling with -O through -O8 (just to make sure! - I know the 
docs say that there is nothing above -O3, but a friend of mine says that 
it goes up to -O5 or -O6 at least) and got exactly the same results.

My friend says that it could be a typecasting problem if that helps.

Thanks for your help!
Warren

bangerth@dealii.org wrote:

> Synopsis: fabs error with -ansi
>
> State-Changed-From-To: open->feedback
> State-Changed-By: bangerth
> State-Changed-When: Fri Dec 20 19:37:38 2002
> State-Changed-Why:
>    The problem you write seems as if for certain numbers the
>    implementation of fabs is doing something wrong, but only
>    on certain machines. Now, fabs is a function that libm
>    implements, not the compiler, so to find out where the
>    problem lies exactly, try the following:
>    
>    - try linking with -static on a machine where it works.
>      This makes sure that not the local libm is taken, but the
>      one from the system where it works. Try the other way
>      round and see whether it then also fails on the machines
>      it worked on previously.
>    - Try what happens when you switch on optimization.
>    
>    Just for the reference, I cannot reproduce the problem
>    on a PIII, but that was to be expected from your report.
>    
>    Thanks
>      Wolfgang
>
> http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8974
>
>
>