Proof of Concept: Binding to and extending C++ objects via a metric
downs
default_357-line at yahoo.de
Wed Dec 9 16:02:29 PST 2009
g wrote:
> downs Wrote:
>
>> I've just committed a module to tools (tools.cpp, http://dsource.org/projects/scrapple/Trunk/tools/tools/cpp.d ) that should enable linking and using any C++ library with D programs without creating a C wrapper for it.
>>
>> The code has been tested with a simple multiple-inheritance sample: http://paste.dprogramming.com/dpv8hpjp
>>
>> The D code to bind to this is http://paste.dprogramming.com/dphlv1ot . It requires a symlink to the tools folder in its directory.
>>
>> Caveats:
>>
>> - D1
>> - Only works on g++4's "newapi" layout and mangling (but should be reasonably portable).
>> - Diamond pattern is untested and unsupported.
>> - Class protection is completely unsupported - public only.
>> - RTTI must be generated manually (normally the compiler would do this). See the D half of the sample.
>> - Dynamic casting from and to generated classes is not implemented.
>> - The C++ code that does this is long and full of special cases, so
>> - For the example, I ended up hardcoding a manual translation between A and B.
>> - If you need dynamic casting, I recommend hardcoding the required paths based on classinfo pointer comparisons.
>> - The C++ DSL parser is not very tested. Occasional bugs may occur.
>> - When building with LDC, fixup_vtable() needs to be called for every newly created C++ class object.
>> - This is because LDC does not yet support initialization from global variable addresses.
>>
>> Building the sample is a two-step process:
>>
>> g++ test.cpp -c -g -o test.o
>> gdc -J. cpp_demo.d tools/cpp.d tools/base.d tools/smart_import.d tools/ctfe.d tools/compat.d tools/text.d tools/tests.d tools/log.d test.o \
>> -o cpptest -lstdc++ -L /usr/lib/gcc/i686-pc-linux-gnu/4.3.2/ -g # adapt library path as appropriate
>>
>>
>> Writing this also gave us what I believe to be a fair contender to Most Horrifying Statement of D Ever Written:
>>
>> fndefs ~= `mixin("extern(C) `~t~` "~`~mname~`~"`~fnparams~`; ");`~'\n'~
>> `mixin("`~fn~`("~refToParamList("Params!(typeof(&"~`~mname~`~"))", isRef!(typeof(mixin("&"~`~mname~`))))~") {
>> return "~`~mname~`~"("~refToValueList(isRef!(typeof(mixin("&"~`~mname~`))))~");
>> }
>> "); `;
>>
>> --downs
>
> if you have problems seeing the first link:
> http://dsource.org/projects/scrapple/browser/trunk/tools/tools/cpp.d
Oops. Sorry for that. (Never a post without an error!)
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