extern C function in a namespace cannot be accessed

[yanghao]

I am new to cppyy, not sure if this is an issue or simply I didn't get the right way to use it.

It seems that if a function is declared as extern "C" then it is not accessible from cppyy.
Here is a quick way to test it:

$ cat test.h
namespace test {
        extern "C" int test_extern_c(void);
        int test_normal(void);
}
$ python3
Python 3.10.0+ (heads/v3.10-dirty:099a94fba3, Nov  5 2021, 13:02:25) [GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cppyy
>>> cppyy.include("test.h")
True
>>> cppyy.gbl.test.test_normal
<cppyy.CPPOverload object at 0x7f1dfb343340>
>>> cppyy.gbl.test.test_extern_c
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: <namespace cppyy.gbl.test at 0x561e5d770300> has no attribute 'test_extern_c'. Full details:
  type object 'test' has no attribute 'test_extern_c'
  'test::test_extern_c' is not a known C++ class
  'test_extern_c' is not a known C++ template
  'test_extern_c' is not a known C++ enum
>>>
>>> cppyy.gbl.test_extern_c
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: <namespace cppyy.gbl at 0x561e5bf3e580> has no attribute 'test_extern_c'. Full details:
  type object '' has no attribute 'test_extern_c'
  'test_extern_c' is not a known C++ class
  'test_extern_c' is not a known C++ template
  'test_extern_c' is not a known C++ enum
>>>

Did I miss anything?

Thanks a lot.

[wlav]

Thanks for the report! Now fixed in repo: wlav/cppyy-backend@068e895

Applying the above, if used from source, requires both rebuilding cppyy-cling and cppyy-backend, which is a bit of a hassle, but I can't think of a workaround, other than providing a manual helper/wrapper. (Which should probably be fine if there are no more than a handful of these functions.)

[yanghao]

@wlav Thanks for confirming this. Yes, right now I just pick up the definition from header files and using cppdef to define it again and it works perfectly fine.