ldc can't link embedded python properly on ubuntu

[ariovistus]

and probably anywhere Py_ENABLE_SHARED is false.
symptom:
ImportError: /usr/lib/python3/dist-packages/numpy/core/multiarray.cpython-32mu.so: undefined symbol: PyExc_SystemError

ramification:
can't use numpy and other extensions

solution: insert -rdynamic early in the link flags. unfortunately, ldc rearranges flag order, and exposes no way to override.

other solution: go back to gcc for link command. please no.

[lomereiter]

Is -rdynamic the only possible workaround? Quick googling shows that many solve this problem just by adding dlopen("libpython<PYTHON_VERSION>.so.1", RTLD_LAZY | RTLD_GLOBAL); before Py_Initialize()

[JohanEngelen]

LDC has recently changed the linker flag order behavior. Please try again, and otherwise open an issue with LDC, thanks!

[ariovistus]

I assume this would be in 1.6?

[JohanEngelen]

Yes indeed, 1.6.0 has what I meant.
I may be remembering things wrong. But we had a discussion and some changes related to linking flags and their order (but perhaps only related to the flags in ldc.conf)

[ariovistus]

Ok. will check it out when I get some time.

[ariovistus]

there wouldn't happen to be a quicker way to install than build from source, would there? on 16.04, apt-get serves 0.17.1

[JohanEngelen]

curl -fsS https://dlang.org/install.sh | bash -s install ldc

[JohanEngelen]

https://dlang.org/download.html

[wilzbach]

@JohanEngelen
FYI: We can do it even a bit shorter: curl i.dlang.io | bash -s ldc

Since yesterday we also have a documentation page for the installer: https://dlang.org/install.html

[ariovistus]

Looks like ubuntu stopped building python with Py_ENABLE_SHARED=false, so this might not be much of an issue anymore.

[JohanEngelen]

@wilzbach

FYI: We can do it even a bit shorter: curl i.dlang.io | bash -s ldc

Brevity here is useless, and harms intelligibility. The original one at least makes it clear that you are downloading a shell script, and that you are installing ldc.

The installer page is very nice. (link needs to be added to the top menu!)

[ariovistus]

ubuntu 12.04 has an appropriate python build.
With pyd from master and ldc 1.6.0, the following code is sufficient to trigger the aforementioned symptom:

auto context = new InterpContext();
context.py_stmts("import numpy");

This issue has been collecting dust long enough that I do not remember how to get link to work with -rdynamic. Will need to play with it.