• abad (23/23) Jun 01 2016 D source:
• Mike Parker (3/26) Jun 01 2016 Try this:
• Mike Parker (4/11) Jun 01 2016 And I don't know if this was just a typo in your post, but also
• abad (10/16) Jun 01 2016 That does work, though I have to explicitly cast it in my caller
• Kagamin (2/10) Jun 01 2016 Can you declare it as const char*const* one the C++ side?
• Jesse Phillips (8/9) Jun 01 2016 Just to state the problem clearly, D's const is transitive, C++

abad <abad.flt gmail.com> writes:

D source:

extern(C++) void thisWorks(const char* test);
extern(C++) void doesNotLink(const char** test);

void main() {
     char* baz1;
     char** baz2;
     thisWorks(baz1);
     doesNotLink(baz2);
}

CPP source:

#include <stdio.h>

void thisWorks(const char* test) {
     printf("hi\n");
}

void DoesNotLink(const char** test) {
     // not reached
}

The error given by the linker:
test.d:(.text._Dmain+0x21): undefined reference to 
`doesNotLink(char const* const*)'

What's happening? I know there are differences in const behavior 
between D and C++, but can't figure a way around it. Any sort of 
casting trick I tried doesn't seem to help.

Mike Parker <aldacron gmail.com> writes:

On Wednesday, 1 June 2016 at 07:09:16 UTC, abad wrote:
 D source:

 extern(C++) void thisWorks(const char* test);
 extern(C++) void doesNotLink(const char** test);

 void main() {
     char* baz1;
     char** baz2;
     thisWorks(baz1);
     doesNotLink(baz2);
 }

 CPP source:

 #include <stdio.h>

 void thisWorks(const char* test) {
     printf("hi\n");
 }

 void DoesNotLink(const char** test) {
     // not reached
 }

 The error given by the linker:
 test.d:(.text._Dmain+0x21): undefined reference to 
 `doesNotLink(char const* const*)'

 What's happening? I know there are differences in const 
 behavior between D and C++, but can't figure a way around it. 
 Any sort of casting trick I tried doesn't seem to help.

Try this:

extern(C++) void DoesNotLink(const(char)**);

Mike Parker <aldacron gmail.com> writes:

On Wednesday, 1 June 2016 at 07:17:04 UTC, Mike Parker wrote:
 On Wednesday, 1 June 2016 at 07:09:16 UTC, abad wrote:

 What's happening? I know there are differences in const 
 behavior between D and C++, but can't figure a way around it. 
 Any sort of casting trick I tried doesn't seem to help.

 Try this:

 extern(C++) void DoesNotLink(const(char)**);

And I don't know if this was just a typo in your post,  but also 
note that you 'D'oesNotLink in the CPP source you pasted and 
'd'oesNotLink in the D code.

abad <abad.flt gmail.com> writes:

On Wednesday, 1 June 2016 at 07:17:04 UTC, Mike Parker wrote:
 On Wednesday, 1 June 2016 at 07:09:16 UTC, abad wrote:

 Try this:

 extern(C++) void DoesNotLink(const(char)**);

That does work, though I have to explicitly cast it in my caller 
as well.
Like this:

doesNotLink(cast(const(char)**)baz2);

It's a bit troublesome as my code will include quite a lot of 
calls like this.

Casting is not necessary with the method call with the single 
pointer argument, as it seems to get const'ed automatically.

 And I don't know if this was just a typo in your post,  but 
 also note that you 'D'oesNotLink in the CPP source you pasted 
 and 'd'oesNotLink in the D code.

That was just a typo.

Kagamin <spam here.lot> writes:

On Wednesday, 1 June 2016 at 07:29:56 UTC, abad wrote:
 That does work, though I have to explicitly cast it in my 
 caller as well.
 Like this:

 doesNotLink(cast(const(char)**)baz2);

 It's a bit troublesome as my code will include quite a lot of 
 calls like this.

 Casting is not necessary with the method call with the single 
 pointer argument, as it seems to get const'ed automatically.

Can you declare it as const char*const* one the C++ side?

Jesse Phillips <Jesse.K.Phillips+D gmail.com> writes:

On Wednesday, 1 June 2016 at 16:16:26 UTC, Kagamin wrote:
 Can you declare it as const char*const* one the C++ side?

Just to state the problem clearly, D's const is transitive, C++ 
it is not. C linkage doesn't care about const, so you can specify 
it however you want. In C++ the const is included in the 
mangling, so it must match the declaration between C++ and D.

Transitive meaning that const will apply to all elements pointed 
to. This is why you see linker complain about not being able to 
find char const * const *