I know I prefer using shared() when interfacing with C. I've tried using __gshared once when interfacing with C code. But I had crashes all the time, using shared instead made my app stable again. It might be related to the way the C code worked, since multiple threads were involved. Anyway.. that's my experience with gshared..
On 12/9/10, Steven Schveighoffer <schvei...@yahoo.com> wrote: > On Thu, 09 Dec 2010 10:15:59 -0500, CrypticMetaphor > <crypticmetapho...@gmail.com> wrote: > >> On 12/9/2010 3:57 PM, Steven Schveighoffer wrote: >>> On Thu, 09 Dec 2010 09:37:03 -0500, CrypticMetaphor >>> <crypticmetapho...@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: >>> >>> ste...@steve-laptop:~/testd$ gcc -c testc.c >>> ste...@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 :-( > > No, not really. TLS is related to threads, but you don't really have to > understand how threads work to understand where things are stored. > > I don't know where it is in the book, but try looking for Thread Local > Storage in the index? > >> But anyway, it should not compile right? >> >> Should I submit a bug report or something? > > Yes please, and be sure to specify that it correctly does not compile on > linux. http://d.puremagic.com/issues/enter_bug.cgi > >> And how I supposed to call the c function? > > Mark the extern(C) integer as __gshared in D. That will put it in the > global namespace instead of TLS. > > e.g.: > > extern(C) { // this is needed to make it available from C > __gshared int globalFromD; > } > > -Steve >
