• Heinz <malagana15 yahoo.es> Feb 13 2009
• Mike Parker <aldacron gmail.com> Feb 13 2009
• Frits van Bommel <fvbommel REMwOVExCAPSs.nl> Feb 13 2009

Heinz <malagana15 yahoo.es> writes:

torhu Wrote:

 On 10.02.2009 19:51, Heinz wrote:
 Heinz Wrote:

 I attached a rar file with the sources just to see what i'm talking about. The
example is from the DMD site. Included is the extern D (ok) and the extern C
(fails). To compile open "compile.bat" and to run the programs use "run.bat".


 Try this:
 alias extern (C) void function(void*) MyDLL_Initialize_fp;
 alias extern (C) void function() MyDLL_Terminate_fp;
 alias extern (C) MyClass function() getMyClass_fp;


Haha! cool man, thanx, it works.
I never though it could be the type but adding extern(C), the program treats
variables as C function pointers. I had no idea at all that i can create
extern(C) variables to be trated as C type. I learned something new today!
Thanks again.

Mike Parker <aldacron gmail.com> writes:

Heinz wrote:
 torhu Wrote:
 
 On 10.02.2009 19:51, Heinz wrote:
 Heinz Wrote:

 I attached a rar file with the sources just to see what i'm talking about. The
example is from the DMD site. Included is the extern D (ok) and the extern C
(fails). To compile open "compile.bat" and to run the programs use "run.bat".


 alias extern (C) void function(void*) MyDLL_Initialize_fp;
 alias extern (C) void function() MyDLL_Terminate_fp;
 alias extern (C) MyClass function() getMyClass_fp;


 Haha! cool man, thanx, it works.
 I never though it could be the type but adding extern(C), the program treats
variables as C function pointers. I had no idea at all that i can create
extern(C) variables to be trated as C type. I learned something new today!
 Thanks again.
 


It doesn't affect normal variables. Calling a function through a 
function pointer, the calling convention still must be known in order 
for parameters to be properly passed. So any time you define a function 
pointer to point to a C function or to pass to a C API as a callback, it 
must have the proper extern linkage.

Frits van Bommel <fvbommel REMwOVExCAPSs.nl> writes:

Mike Parker wrote:
 Heinz wrote:
 torhu Wrote:

 On 10.02.2009 19:51, Heinz wrote:
 Heinz Wrote:

 I attached a rar file with the sources just to see what i'm talking 
 about. The example is from the DMD site. Included is the extern D 
 (ok) and the extern C (fails). To compile open "compile.bat" and to 
 run the programs use "run.bat".


 alias extern (C) void function(void*) MyDLL_Initialize_fp;
 alias extern (C) void function() MyDLL_Terminate_fp;
 alias extern (C) MyClass function() getMyClass_fp;


 Haha! cool man, thanx, it works.
 I never though it could be the type but adding extern(C), the program 
 treats variables as C function pointers. I had no idea at all that i 
 can create extern(C) variables to be trated as C type. I learned 
 something new today!
 Thanks again.


 It doesn't affect normal variables. Calling a function through a 
 function pointer, the calling convention still must be known in order 
 for parameters to be properly passed. So any time you define a function 
 pointer to point to a C function or to pass to a C API as a callback, it 
 must have the proper extern linkage.


Actually, extern(C) does affect normal variables. In particular, it 
affects their name mangling. (And if the type of the variable includes a 
'raw' function pointer type (not an alias/typedef to one), I'm pretty 
sure it also modifies that type to use a C calling convention function 
pointer type)

The example above, though, does not directly affect any variables 
because they're only alias declarations.