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Python 3.4 & undefined reference to `_PyGen_Send' #1968

KeyWeeUsr opened this issue Oct 30, 2017 · 2 comments

Python 3.4 & undefined reference to `_PyGen_Send' #1968

KeyWeeUsr opened this issue Oct 30, 2017 · 2 comments


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KeyWeeUsr commented Oct 30, 2017

  • GCC from mingwpy-0.1.0b3
  • Python 3.4.4
  • Cython 0.27.2

I think it was introduced in 0.27, our build reports the issue for Python 3.4 versions. See this commit - 72acc2c and

// _PyGen_Send() is not exported before Py3.6

Also notice 3.3+ referenced here and not in the rest of the lines:

#if CYTHON_COMPILING_IN_CPYTHON && PY_VERSION_HEX >= 0x03030000 && (!defined(_MSC_VER) || PY_VERSION_HEX >= 0x03060000)


writing build\temp.win32-3.4\Release\kivy\_event.def
C:\Python34\Scripts\gcc.exe -shared -s build\temp.win32-3.4\Release\kivy\_event.o build\temp.win32-3.4\Release\kivy\_event.def -LC:\Python34\libs -LC:\Python34\libs -LC:\Python34\PCbuild -lpython34 -lmsvcr100 -o C:\projects\kivy\kivy\_event.pyd -lm
\temp.win32-3.4\Release\kivy\_event.o:_event.c:(.text+0x45da): undefined reference to `_PyGen_Send'
build\temp.win32-3.4\Release\kivy\_event.o:_event.c:(.text+0x9290): undefined reference to `_PyGen_Send
collect2.exe: error: ld returned 1 exit status
 error: command 'C:\\Python34\\Scripts\\gcc.exe' failed with exit status 1
Failed with exit code 1

The file _event.pxd hasn't changed for quite a while + the build worked fine with <0.27.

Any ideas how to fix it without downgrading to 0.26?

@scoder scoder added this to the 0.27.3 milestone Oct 31, 2017
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scoder commented Oct 31, 2017

MinGW probably doesn't set _MSC_VER (because, why should it?), so the guard doesn't apply and opens up the special case for Python < 3.6. Problem is, it shouldn't guard against MSVC since this is a platform issue, not a compiler thing. The _PyGen_Send() function is not properly exported before python/cpython@833c626, and the fact that Linux systems do not care is not a good excuse for blaming it on Windows (let alone MSVC, although that is always a good target for blaming). I'll change the guard to defined(__linux__) for 0.27.3.

@scoder scoder closed this as completed in cd3e189 Oct 31, 2017
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@scoder Thanks for such a quick response and for the fix! :) Any ETA for 0.27.3?

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