Hi,

the problem I want to solve is that some functions should be exported to a DLL (or not) based on a version identifier. This probably could be done also by editing the .def file but would be rather inconvenient.


Example:

----------

version(DLL_C)   // If we want a DLL interface for C
{
  export:
  extern(C):
}

int forC_aaa()
{...}

int forC_bbb()
{...}

noexport:  // Stop exporting
extern(D):  // Stop C linkage



int helper()  // Never exported
{...}



version(DLL_D)   // If we want a DLL interface for D
{
  export:
}

int aaa()
{...}

int bbb()
{...}

noexport:  // Stop exporting

----------


It would be nice also if it could be written this way:

version(DLL_D) {export} int aaa()

But maybe hard to implement.



Michael

> version(DLL_C)   // If we want a DLL interface for C
> {
>   export:
>   extern(C):
> }

AFAIK, this will not work as you expect! version() is not the same as #ifdef and friends, where you "include" something. The scope of export: and extern: ends at the closing brace! Anything after version() will have the normal D linkage.

Ciao
uwe

On Tue, 07 Jun 2005 15:30:14 -0400, Uwe Salomon <post@uwesalomon.de> wrote:

>> version(DLL_C)   // If we want a DLL interface for C
>> {
>>   export:
>>   extern(C):
>> }
>
> AFAIK, this will not work as you expect! version() is not the same as #ifdef and friends, where you "include" something. The scope of export: and extern: ends at the closing brace! Anything after version() will have the normal D linkage.
>
> Ciao
> uwe

Sometimes { } doesn't introduce a new scope, depending on the statement. In this case I don't think it does and so it should work how he is using it.

Since 'export' is a protection attribute, you can end any 'export:' attribute-statement by introducing a new protection attribute, such as 'public'.  In other words:

# version(DLL_C) {
#   export:
#   extern(C):
# }
#
# int forC_aaa() { ... }
# int forC_bbb() { ... }
#
# public:
# extern(D): // default is D, but it may be good to be explicit here
#
# int helper() { ... }
#
# version(DLL_D) {
#   export:
# }
#
# int aaa() { ... }
# int bbb() { ... }
#
# public:


> It would be nice also if it could be written this way:
> 
> version(DLL_D) {export} int aaa()
> 
> But maybe hard to implement.

Maybe the 'alias' statement could be given a new case for attribute symbols...  so you could do something like:

# version (DLL_D) { alias export a_AttrProtection; }
# else            { alias public a_AttrProtection; }
#
# a_AttrProtection int aaa() { ... }

-- Chris Sauls

Uwe Salomon wrote:
> > version(DLL_C)   // If we want a DLL interface for C
> > {
> >   export:
> >   extern(C):
> > }
> 
> AFAIK, this will not work as you expect! version() is not the same as #ifdef and friends, where you "include" something. The scope of export: and extern: ends at the closing brace! Anything after version() will have the normal D linkage.
> 
> Ciao
> uwe


I tried it and it works (tested with DMD 0.124).


Michael

Chris Sauls wrote:
> Since 'export' is a protection attribute, you can end any 'export:' attribute-statement by introducing a new protection attribute, such as 'public'.  In other words:
> 
> # version(DLL_C) {
> #   export:
> #   extern(C):
> # }
> #
> # int forC_aaa() { ... }
> # int forC_bbb() { ... }
> #
> # public:
> # extern(D): // default is D, but it may be good to be explicit here
> #
> # int helper() { ... }
> #
> # version(DLL_D) {
> #   export:
> # }
> #
> # int aaa() { ... }
> # int bbb() { ... }
> #
> # public:


Thank you!


Michael