How to define syscall() in freebsd?

[Joakim]

On Thursday, 12 July 2018 at 13:55:58 UTC, Brian wrote:
> the code is error:
> extern (C) nothrow @nogc size_t syscall(size_t ident);
> extern (C) nothrow @nogc size_t syscall(size_t ident, size_t 
> arg0);
> extern (C) nothrow @nogc size_t syscall(size_t ident, long* 
> arg0);
>
> long tid;
> syscall(SYS_thr_self, &tid);
> writeln(tid);
>
> Error: Function type does not match previously declared 
> function with the same mangled name: syscall

Just like in C, you cannot declare multiple extern(C) functions 
with the same name.

> Change to:
> extern (C) nothrow @nogc size_t syscall(size_t ident);
> extern (C) nothrow @nogc size_t syscall(size_t ident, size_t 
> arg0);
> extern (C) nothrow @nogc size_t syscall(size_t ident, long* 
> arg0);
>
> long tid;
> syscall(SYS_thr_self, &tid);
> writeln(tid);

What did you change? I see no difference.

> Error: none of the overloads of syscall are callable using 
> argument types (int, long*), candidates are:
> source/app.d(3,33):        kiss.sys.syscall.syscall(ulong ident)
> source/app.d(4,33):        kiss.sys.syscall.syscall(ulong 
> ident, ulong arg0)

Look at the types: the error says you're passing an int and long* 
on 64-bit to functions with different types.

> Change to:
> // extern (C) nothrow @nogc size_t syscall(size_t ident);
> // extern (C) nothrow @nogc size_t syscall(size_t ident, size_t 
> arg0);
> extern (C) nothrow @nogc size_t syscall(size_t ident, long* 
> arg0);
>
> long tid;
> syscall(SYS_thr_self, &tid);
> writeln(tid);
>
> result:
>
> 100567

Probably related to first issue mentioned- you cannot overload C 
functions- maybe the compiler finds the third now that you 
removed the disallowed overloads.