[Tinycc-devel] RE :Re: sinf/sin problems

[Christian JULLIEN]

Hi,

Maybe having --strict-prototype flag could help us to detect this situation.



> ----- message d'origine -----
> De : "Daniel Glöckner" <address@hidden>
> date mer. 24/12/2014 13:54 (GMT +01:00)
> À : "address@hidden" <address@hidden>
> Objet : Re: [Tinycc-devel] sinf/sin problems
>
> Hi,
>
> just some nit-picking:
>
> On Wed, Dec 24, 2014 at 04:46:14PM +0800, Lee Duhem wrote:
> > `sinf' is defined in libm.so, you need to link with it.
>
> on Linux
>
> > As explained by Aharon, c compiler will offer an implicit declaration
> > for any undeclared function that it saw, and the return type of this
> > implicit declaration is `int'. Therefore those return values of `sin'
> > in your code will be converted to `int' first, then convert to `double'
> > for `printf' to print.
>
> The return value of a function returning an int is not passed in the
> register where a double would be returned, so you might get garbage
> that is in no way related to the input.
>
> On top of that the int is not cast to double in
> printf("\n%f", sin(1.0));
> The bytes on the stack are simply reinterpreted as double, so
> printf("%f\n", 1);
> will not print 1.000000.  That's because of the ellipsis in the
> declaration of printf.
>
> Best regards,
>
>   Daniel
>
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