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digitalmars.D - Trying to add C++ header generation to dmd

reply Gregor =?UTF-8?B?TcO8Y2ts?= <gregormueckl gmx.de> writes:
Hi!

I tried to hack a bit on dmd to have it generate a C++ header for 
a D module. I've copied the visitor in hdrgen.d and did truly 
terrible things to it, to the point where I don't feel confident 
that I want to show that code to anyone.

So now I get something almost resembling C++ code for a few 
really trivial definitions in the input D module. But that is for 
all definitions, not just the ones marked external(C++).

This is the point where I'm actually stumped now. The 
PrettyPrintVisitor, which I used as a template, does not really 
make it easy to discover the context of a visited AST node. In 
particular, I don't know how to determine if one of the parent 
nodes possess the required extern(C++) linkage specification to 
be considered for exporting.

If there was a way for the visitor to know when the subtree below 
a certain node has been visited completely, it could then 
trivially track linkage as a kind of a contextual information.

So to anyone who knows dmd better than me: how would you go about 
implementing the visitor in such a way that it only exports the 
correct AST subtrees?

Gregor
Mar 19 2019
next sibling parent albr <albr none.such> writes:
On Tuesday, 19 March 2019 at 20:55:34 UTC, Gregor Mückl wrote:

 If there was a way for the visitor to know when the subtree 
 below a certain node has been visited completely, it could then 
 trivially track linkage as a kind of a contextual information.


DFS traversal?
Mar 20 2019
prev sibling parent reply Jacob Carlborg <doob me.com> writes:
On 2019-03-19 21:55, Gregor Mückl wrote:

 Hi!
 
 I tried to hack a bit on dmd to have it generate a C++ header for a D 
 module. I've copied the visitor in hdrgen.d and did truly terrible 
 things to it, to the point where I don't feel confident that I want to 
 show that code to anyone.
 
 So now I get something almost resembling C++ code for a few really 
 trivial definitions in the input D module. But that is for all 
 definitions, not just the ones marked external(C++).
 
 This is the point where I'm actually stumped now. The 
 PrettyPrintVisitor, which I used as a template, does not really make it 
 easy to discover the context of a visited AST node. In particular, I 
 don't know how to determine if one of the parent nodes possess the 
 required extern(C++) linkage specification to be considered for exporting.
 
 If there was a way for the visitor to know when the subtree below a 
 certain node has been visited completely, it could then trivially track 
 linkage as a kind of a contextual information.
 
 So to anyone who knows dmd better than me: how would you go about 
 implementing the visitor in such a way that it only exports the correct 
 AST subtrees?


I'm not sure if you need to look at the parent. Every declaration has a 
"linkage" field [1] identifying if it's C++, D or something else. 
Classes and structs, which don't inherit from Declaration, has a 
"classKind" field [2].

You can also have a look at this work in progress PR [3].

[1] 
https://github.com/dlang/dmd/blob/3a298e504707ccd8d633c6ea5511d46c5758fa8b/src/dmd/declaration.d#L289

[2] 
https://github.com/dlang/dmd/blob/3a298e504707ccd8d633c6ea5511d46c5758fa8b/src/dmd/aggregate.d#L86

[3] https://github.com/dlang/dmd/pull/8591

-- 
/Jacob Carlborg
Mar 20 2019
parent reply Gregor =?UTF-8?B?TcO8Y2ts?= <gregormueckl gmx.de> writes:
On Wednesday, 20 March 2019 at 10:27:27 UTC, Jacob Carlborg wrote:

 On 2019-03-19 21:55, Gregor Mückl wrote:

 [snip]


 I'm not sure if you need to look at the parent. Every 
 declaration has a "linkage" field [1] identifying if it's C++, 
 D or something else. Classes and structs, which don't inherit 
 from Declaration, has a "classKind" field [2].

 You can also have a look at this work in progress PR [3].

 [1] 
 https://github.com/dlang/dmd/blob/3a298e504707ccd8d633c6ea5511d46c5758fa8b/src/dmd/declaration.d#L289

 [2] 
 https://github.com/dlang/dmd/blob/3a298e504707ccd8d633c6ea5511d46c5758fa8b/src/dmd/aggregate.d#L86

 [3] https://github.com/dlang/dmd/pull/8591


Do these fields extend properly to children? Consider the 
following code:

extern(C++) class C
{
   int foo(int a, int b);
}

Will foo be marked with C++ linkage? The parameters as well? That 
would simplify the matter a lot.

The pull request does indeed look useful. Thanks!
Mar 20 2019
next sibling parent Stefan Koch <uplink.coder googlemail.com> writes:
On Wednesday, 20 March 2019 at 14:26:17 UTC, Gregor Mückl wrote:

 On Wednesday, 20 March 2019 at 10:27:27 UTC, Jacob Carlborg 
 wrote:

 [...]


 Do these fields extend properly to children? Consider the 
 following code:

 extern(C++) class C
 {
   int foo(int a, int b);
 }

 Will foo be marked with C++ linkage? The parameters as well? 
 That would simplify the matter a lot.

 The pull request does indeed look useful. Thanks!


It _should_ you can test it by looking if the mangle changes from 
the class without extern(C++).
Mar 20 2019
prev sibling parent Jacob Carlborg <doob me.com> writes:
On 2019-03-20 15:26, Gregor Mückl wrote:


 Do these fields extend properly to children? Consider the following code:
 
 extern(C++) class C
 {
    int foo(int a, int b);
 }
 
 Will foo be marked with C++ linkage? 


"foo" will definitely have C++ linkage.

The parameters as well? That would simplify the matter a lot.

Not sure. I don't think that matters in this case.

-- 
/Jacob Carlborg
Mar 20 2019