fputs, stdout

Jonathan M Davis newsgroup.d at jmdavisprog.com
Tue Nov 7 04:46:12 UTC 2017


On Tuesday, November 07, 2017 04:34:30 Tony via Digitalmars-d-learn wrote:
> There is a fputs/stdout in core.stdc.stdio.  std.stdio "public
> imports" that:
>
> "public import core.stdc.stdio;"
>
> Wondering why:
>
> import core.stdc.stdio : fputs;
> import core.stdc.stdio : stdout;
>
> void main()
> {
>     fputs( cast(const char *)"hello world\n",stdout);
> }
>
> compiles and runs, but if I change the imports to:
>
> import std.stdio : fputs;
> import std.stdio : stdout;
>
> I get this compile error:
>
> fputs_test.d(11): Error: function core.stdc.stdio.fputs (scope
> const(char*) s, shared(_IO_FILE)* stream) is not callable using
> argument types (const(char*), File)

stdout in core.stdc.stdio and stdout in std.stdio are two different things.
In core.stdc.stdio it's a FILE*, and in std.stdio it's std.stdio.File.
Basically, core.stdc.stdio gives you the C version, and std.stdio gives you
the D version. However, there is no fputs in std.stdio. Rather, std.stdio
publicly imports core.stdc.stdio. So, it's the same fputs in
core.stdc.stdio, and it expects a FILE*, whereas since you import stdout
from std.stdio, you got the File, not the FILE*. So, they're not compatible.

- Jonathan M Davis



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