🚀 go-pugleaf

In article <1992Nov3.005333.17727@Princeton.EDU> rhl@grendel.Princeton.EDU (Robert Lupton the Good) writes:
> Is the following Standard Conforming?
>    #include <math.h>
>    extern double sin();

No. Section 7.1.7 of the ISO standard:

| ... a library function should not be declared explicitly if its header
| is included.

> I'd have said yes (as the sin() merely says that I don't know about its
> arguments), but it is rejected by the IBM c89 compiler%
> % their math.h defines sin as
>	#define sin(x) __sin(x)

Which is why that restriction exists in the compiler. A more obvious
use of this is:

    #define malloc(s) (__using_D_malloc ? __D_malloc (s) : __malloc (s))
    #define free(p)   (__using_D_malloc ? __D_free (p)   : __free (p)  )

where the D malloc family is some special debugging malloc.

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