Calling C functions

[CrypticMetaphor]

On 12/9/2010 3:57 PM, Steven Schveighoffer wrote:
> On Thu, 09 Dec 2010 09:37:03 -0500, CrypticMetaphor
> <CrypticMetaphor88 at gmail.com> wrote:
>
>> I found this page that describes how to call c functions from D.
>>
>> I found this page that describes how:
>> http://arsdnet.net/dtips/#cfunc
>>
>> on that page he uses gcc, and I use dmc, but I get different results.
>> This is what I did
>>
>> // cfile.c file
>> extern int globalFromD;
>>
>> void functionFromC(int a) {
>> globalFromD = a;
>> }
>> // end cfile.c
>>
>> // dfile.d
>> extern(C) { // this is needed to make it available from C
>> int globalFromD;
>> }
>> extern(C) { // also needed when listing the prototypes for your C
>> functions
>> void functionFromC(int);
>> }
>>
>> import std.stdio; // for writefln
>>
>> int main() {
>> globalFromD = 100;
>> writefln("%d", globalFromD);
>>
>> functionFromC(500);
>> writefln("%d", globalFromD);
>>
>> return 0;
>> }
>> // end dfile.d
>>
>> I compile with:
>> dmc -c cfile.c
>> And I get an cfile.obj, which is the object code (.o in gcc).
>> Then I compile the D code
>> dmd dfile.d cfile.obj
>> and I get no errors, so I run it, the result:
>> // start result
>> C:\DCode\libtest>dfile.exe
>> 100
>> 100
>>
>> C:\DCode\libtest>
>> // end result
>>
>> Why is it still 100? It should be 500. I don't think functionFromC(
>> int ) is being called, and I can't really find any other sources that
>> clearly explain how to do this simple stuff, so can anyone explain how
>> to fix it?
>
> I'm guessing that this is a later D2 compiler? If so, then the default
> storage for globals is in Thread Local Storage (local to each thread).
> This could explain why it doesn't work, because globalFromD is in TLS in
> D-land, but in the normal global space in C-land. But there is no
> declaration of the global-space version then, so I'm surprised it would
> compile then.
>
> I'm really curious why this doesn't work but does compile.
>
> What version of D compiler are you using?
>
> When using dmd 2.050 on linux I get this error when compiling:
>
> steves at steve-laptop:~/testd$ gcc -c testc.c
> steves at steve-laptop:~/testd$ ~/dmd-2.050/linux/bin/dmd testcallc.d testc.o
> /usr/bin/ld: globalFromD: TLS definition in testcallc.o section .tbss
> mismatches non-TLS reference in testc.o
> testc.o: could not read symbols: Bad value
> collect2: ld returned 1 exit status
> --- errorlevel 1
>
> Maybe it's a bug in Windows dmd?
>
> -Steve

Yeah I am using D2

dmc version: 8.42n
dmd version: 2.050

Windows XP. But yeah, it compiles

here is a screenshot:
http://img813.imageshack.us/img813/8230/testu.gif

So I gotta read more about threads eh? But that's all the way at the end 
of the book :-(

But anyway, it should not compile right?

Should I submit a bug report or something?
And how I supposed to call the c function?