c standard

[Chris Hodgins]

Florian Hengstberger wrote:
> Following is possible with gcc and g++:
> 
> #include <math.h>
> 
> double sin(double)
> {
>  return 1;
> }
> 
> int main()
> {
>  sin(1);
>  return 1;
> }
> 
> Why I don't get any warnings like:
> 
> sin prevously defined in math.h ...
> 
> when I compile with -Wall -pedantic -ansi.
> 
> Why is it possible to overwrite the definition of sin,
> is this part of the standard?
> 
> Secondly the definition (not declaration) of double sin(double)
> misses a variable!
> Is this ok, when the variable is not referenced in the code?
> 
> Thanks in advance,
> Florian
> 
> ------------------------------------------------------
> Linux/BSD: The daemons are not longer just in my head!
> ------------------------------------------------------
> Florian Hengstberger
> e0025265 at student.tuwien.ac.at
> http://stud3.tuwien.ac.at/~e0025265
> ------------------------------------------------------
> 
> 
> 
> 
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> 

I would address your question to the comp.lang.c newsgroup.  They are 
very knowledgable about such things.

Chris