The subject basically says it all. The C function uses the argument to call fprintf and also passes it to other functions where it's used to call fileno, fprintf or putc.

On Wednesday, 4 July 2018 at 01:06:36 UTC, Joe wrote:
> The subject basically says it all. The C function uses the argument to call fprintf and also passes it to other functions where it's used to call fileno, fprintf or putc.

Like you would with C's fprintf (https://dlang.org/phobos/core_stdc_stdio.html#.fprintf).
For example, this is a valid D program:

---
void main(string[] args)
{
    import core.stdc.stdio;
    FILE* pFile;
    int n;
    char[100] name;

    pFile = fopen ("myfile.txt","w"); // string literals are zero-terminated
    for (n=0 ; n<3 ; n++)
    {
        puts("please, enter a name: ");
        gets(name.ptr);
        fprintf pFile, "Name %d [%-10.10s]\n",n+1,name.ptr);
    }
    fclose(pFile);
}
---

(example from http://www.cplusplus.com/reference/cstdio/fprintf)

So just add the declaration to your D file:

---
extern(C) void myCfunction(FILE* stream);
---

and as long as you link your program into the D binary, you should be good to go.
For larger C bases, tools like dstep or dpp can help translating C/C++ header files to D.

On Wednesday, 4 July 2018 at 01:58:15 UTC, Seb wrote:
> So just add the declaration to your D file:
>
> ---
> extern(C) void myCfunction(FILE* stream);
> ---

I do have a similar declaration in D.  It appears the problem is that the C program I'm trying to convert passes stdout as the argument and the D compiler complains somewhat like the following:


Error: function foo.main.myCfunction (shared(_IO_FILE)* stream) is not callable using argument types (File)

So I guess the question is what to pass instead of stdout.

On Wednesday, 4 July 2018 at 02:08:11 UTC, Joe wrote:
> On Wednesday, 4 July 2018 at 01:58:15 UTC, Seb wrote:
>> So just add the declaration to your D file:
>>
>> ---
>> extern(C) void myCfunction(FILE* stream);
>> ---
>
> I do have a similar declaration in D.  It appears the problem is that the C program I'm trying to convert passes stdout as the argument and the D compiler complains somewhat like the following:
>
>
> Error: function foo.main.myCfunction (shared(_IO_FILE)* stream) is not callable using argument types (File)
>
> So I guess the question is what to pass instead of stdout.

Hmm, calling e.g. fprintf with stdout should just work:

---
void main()
{
    import core.stdc.stdio;
    fprintf(stdout, "Hello %s", "world".ptr);
}
---

Could you maybe provide your whole code?

On Wednesday, 4 July 2018 at 02:16:00 UTC, Seb wrote:
> Hmm, calling e.g. fprintf with stdout should just work:
>
> ---
> void main()
> {
>     import core.stdc.stdio;
>     fprintf(stdout, "Hello %s", "world".ptr);
> }
> ---
>
> Could you maybe provide your whole code?

This short test program shows the error:

---
import std.stdio;


void main()
{
    extern (C) void list(FILE *fd);
    list(stdout);
}
---

Now I fixed this by changing the import to core.stdc.stdio. I guess the problem is if you import std.stdio (which brings in the other one), there are two slightly incompatible stdout's and the D takes precedence.

On Wednesday, 4 July 2018 at 02:54:47 UTC, Joe wrote:
> Now I fixed this by changing the import to core.stdc.stdio. I guess the problem is if you import std.stdio (which brings in the other one), there are two slightly incompatible stdout's and the D takes precedence.

If you import both modules (or even I think if just the D std.stdio, since it publicly imports the other), you can specify the C one by using its full name:

core.stdc.stdio.stdout

where you use it. of course you can also alias it to something shorter.

On Wednesday, 4 July 2018 at 02:54:47 UTC, Joe wrote:
> On Wednesday, 4 July 2018 at 02:16:00 UTC, Seb wrote:
>> Hmm, calling e.g. fprintf with stdout should just work:
>>
>> ---
>> void main()
>> {
>>     import core.stdc.stdio;
>>     fprintf(stdout, "Hello %s", "world".ptr);
>> }
>> ---
>>
>> Could you maybe provide your whole code?
>
> This short test program shows the error:
>
> ---
> import std.stdio;
>
>
> void main()
> {
>     extern (C) void list(FILE *fd);
>     list(stdout);
> }
> ---
>
> Now I fixed this by changing the import to core.stdc.stdio. I guess the problem is if you import std.stdio (which brings in the other one), there are two slightly incompatible stdout's and the D takes precedence.

`stdout.getFP` (stdout is of the D std.stdio.File struct type and with getFP you get the underlying FILE*)