[pypy-dev] cppyy fails to build on gcc 5 and clang

[Tobias Oberstein]

Hi Wim,

Am 18.01.2017 um 18:34 schrieb wlavrijsen at lbl.gov:
> Hi Tobias,
>
>> unknown type code: P
>> 1
>> unknown type code: ???
>> -178968160
>> 77
>
> that falls in the category "should never happen." Arguments are passed as
> a patch of memory, with a type code indicating how the individual arguments
> should be treated. The only way this can be wrong, is if the offset is
> wrong. I don't understand how that can happen: the offset is provided at
> run-time by the backend, where it is compiled in. The pypy-side module
> then uses that offset, so there should be only one value throughout.
>
> Still, is pypy-c build with a different compiler than the pip? Not that I

Yes. I am using

https://github.com/squeaky-pl/portable-pypy

and this is built with GCC 6.2.0.

As there isn't a standard C++ ABI, this would explain all sorts of weird 
things happening.

Or does clang deliberately try to follow gcc ABI?

I am aware that the term "C++ ABI" is an oxymoron in a way .. what's the 
ABI of a templated template? =)

>
> Also, can you try the following (this is not a public interface):

Doesn't work for me:

oberstet at thinkpad-t430s:~/scm/oberstet/scratchbox/cpp/capnproto/test1$ 
pypy MyClass.py
unknown type code: �
1
unknown type code:
1294245728
77

oberstet at thinkpad-t430s:~/scm/oberstet/scratchbox/cpp/capnproto/test1$ pypy
Python 2.7.12 (aff251e543859ce4508159dd9f1a82a2f553de00, Nov 12 2016, 
08:50:18)
[PyPy 5.6.0 with GCC 6.2.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
 >>>> import cppyy
 >>>> cppyy.gbl.gInterpreter.Declare("""
.... class MyClass {
.... public:
....     MyClass(int i = -99) : m_myint(i) {}
....         int GetMyInt() { return m_myint; }
....             void SetMyInt(int i) { m_myint = i; }
....             public:
....                 int m_myint;
....                 };""")
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
AttributeError: <class '__main__.::'> object has no attribute 
'gInterpreter' (details: "function 'cppyy_get_template' not found in 
library 'libcppyy_backend.so'")
 >>>>

--

Given all these problems even running a basic example (I haven't even 
got to capnproto generated C++ .. and this is heavily templated code, so 
even more will go wrong), and given that I have a specific use case 
(captnproto) rather than a general need to wrap C++, I think I will 
evaluate capnpy ..

--

But I think we didn't waste time:

- 2 bugs identified and fixed in cppyy
- using clang _might_ work, but pypy binaries are gcc most of the time, 
and that leads to more issues

So I think gcc 5 support is more important:

"Found GCC compiler with new ABI. Cling does not support the GCC 5 ABI yet"

The bundled Cling is too old? I am totally guessing here .. in fact I 
don't really know what I am doing;)

Cheers,
/Tobias