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python script converted to C code via Cython is throwing this error upon execution: undefined symbol: PyObject_SelfIter

I converted a Python script to C code via Cython, creating "test.c". I then compile with:
gcc -static test.c -I/home/me/Python-3.9.12/include/python3.9 -o test.exe -L/home/me/Python-3.9.12/lib -lpython3.9 -lpthread -lutil -lrt -lm -ldl
When I run "test.exe" I get this error:
Original error was: /home/me/NEWER/numpy/core/_multiarray_umath.cpython-39-x86_64-linux-gnu.so: undefined symbol: PyObject_SelfIter
What I don't understand is that the symbol PyObject_SelfIter is defined in libpython3.9.a which I link in as seen in the compilation line. Why doesn't this linking take care of the undefined symbol noted above? How can I get around this error?
2 notes:
I am linking statically because I want to run the resulting executable on an Android system
as a test, I tried compiling without the -static flag, and the executable still yields the same error
thanks for any tips.

How to solve issues with compiling python file using Cython? [duplicate]

Now that I've successfully installed Cython on Windows 7, I try to compile some Cython code using Cython, but gcc makes my life hard.
cdef void say_hello(name):
print "Hello %s" % name
Using gcc to compile the code throws dozens of undefined reference to -erros, and I'm pretty sure the libpython.a is available (as the installation tutorial said, undefined reference to -errors are thrown if this file is missing).
$ cython ctest.pyx
$ gcc ctest.c -I"C:\Python27\include"
C:\Users\niklas\AppData\Local\Temp\cckThGrF.o:ctest.c:(.text+0x1038): undefined reference to `_imp__PyString_FromStringAndSize'
C:\Users\niklas\AppData\Local\Temp\cckThGrF.o:ctest.c:(.text+0x1075): undefined reference to `_imp___Py_TrueStruct'
C:\Users\niklas\AppData\Local\Temp\cckThGrF.o:ctest.c:(.text+0x1086): undefined reference to `_imp___Py_ZeroStruct'
C:\Users\niklas\AppData\Local\Temp\cckThGrF.o:ctest.c:(.text+0x1099): undefined reference to `_imp___Py_NoneStruct'
C:\Users\niklas\AppData\Local\Temp\cckThGrF.o:ctest.c:(.text+0x10b8): undefined reference to `_imp__PyObject_IsTrue'
c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.2/../../../libmingw32.a(main.o):main.c:(.text+0xd2): undefined reference to `WinMain#16'
collect2: ld returned 1 exit status
The weird thing is, using pyximport* or a setup-script works pretty fine, but it's both not very handy when still working on a module.
How to compile those .c files generated with Cython using gcc ?
or any other compiler, important is that it will work !
*pyximport: Is it normal that only python-native functions and classes are contained in the imported module and not cdef-functions and classes ?
like:
# filename: cython_test.pyx
cdef c_foo():
print "c_foo !"
def foo():
print "foo !"
c_foo()
import pyximport as p; p.install()
import cython_test
cython_test.foo()
# foo !\nc_foo !
cython_test.c_foo()
# AttributeError, module object has no attribute c_foo
UPDATE
Calling $ gcc ctest.c "C:\Python27\libs\libpython27.a" kills the undefined reference to -erros, but this one:
c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.2/../../../libmingw32.a(main.o):main.c:(.text+0xd2): undefined reference to `WinMain#16'

Try:
gcc -c -IC:\Python27\include -o ctest.o ctest.c
gcc -shared -LC:\Python27\libs -o ctest.pyd ctest.o -lpython27
-shared creates a shared library. -lpython27 links with the import library C:\Python27\libs\libpython27.a.

That is a linker (ld) error and not a compiler error. You should provide the path to the library (-l and -L) and not only to the headers (-I).

Embeded python3.6 with MinGW in C++ fail on linking

Try to embed python3.6 in C++ on Win10 64bit system.
Python is installed by python-3.6.1-amd64.exe.
The CMakeList.txt is showing below
cmake_minimum_required(VERSION 3.8)
project(EmbedPython)
set(CMAKE_CXX_STANDARD 11)
set(SOURCE_FILES main.cpp)
find_package(PythonLibs REQUIRED)
include_directories(${PYTHON_INCLUDE_DIRS})
add_executable(EmbedPython ${SOURCE_FILES} ${PYTHON_INCLUDE_DIRS})
target_link_libraries(EmbedPython ${PYTHON_LIBRARIES})
And CMake found the Python package.
PYTHON_INCLUDE_DIR C:/Program Files (x86)/Python36/include
PYTHON_LIBRARY C:/Program Files (x86)/Python36/libs/python36.lib
Find a comment on github it's talking about the API problem.
# used to embed python script
find_package(PythonLibs 2.7 REQUIRED) # this has to be 2.7 because the 3.0 API requires argv to be wchar_t** rather than the default char**
include_directories(${PYTHON_INCLUDE_DIRS})
target_link_libraries( assignment ${PYTHON_LIBRARIES})
The errors below is what I'm facing.
[ 50%] Building CXX object CMakeFiles/EmbedPython.dir/main.cpp.obj
[100%] Linking CXX executable EmbedPython.exe
CMakeFiles\EmbedPython.dir/objects.a(main.cpp.obj): In function `main':
D:/Projects/EmbedPython/main.cpp:16: undefined reference to `_imp__Py_Initialize'
D:/Projects/EmbedPython/main.cpp:17: undefined reference to `_imp__PyUnicode_DecodeFSDefault'
D:/Projects/EmbedPython/main.cpp:20: undefined reference to `_imp__PyImport_Import'
D:/Projects/EmbedPython/main.cpp:24: undefined reference to `_imp__PyObject_GetAttrString'
D:/Projects/EmbedPython/main.cpp:27: undefined reference to `_imp__PyCallable_Check'
D:/Projects/EmbedPython/main.cpp:28: undefined reference to `_imp__PyTuple_New'
D:/Projects/EmbedPython/main.cpp:30: undefined reference to `_imp__PyLong_FromLong'
D:/Projects/EmbedPython/main.cpp:38: undefined reference to `_imp__PyTuple_SetItem'
D:/Projects/EmbedPython/main.cpp:40: undefined reference to `_imp__PyObject_CallObject'
D:/Projects/EmbedPython/main.cpp:43: undefined reference to `_imp__PyLong_AsLong'
D:/Projects/EmbedPython/main.cpp:49: undefined reference to `_imp__PyErr_Print'
D:/Projects/EmbedPython/main.cpp:55: undefined reference to `_imp__PyErr_Occurred'
D:/Projects/EmbedPython/main.cpp:56: undefined reference to `_imp__PyErr_Print'
D:/Projects/EmbedPython/main.cpp:63: undefined reference to `_imp__PyErr_Print'
D:/Projects/EmbedPython/main.cpp:67: undefined reference to `_imp__Py_FinalizeEx'
collect2.exe: error: ld returned 1 exit status
mingw32-make.exe[3]: *** [EmbedPython.exe] Error 1
mingw32-make.exe[2]: *** [CMakeFiles/EmbedPython.dir/all] Error 2
mingw32-make.exe[1]: *** [CMakeFiles/EmbedPython.dir/rule] Error 2
mingw32-make.exe: *** [EmbedPython] Error 2
CMakeFiles\EmbedPython.dir\build.make:96: recipe for target 'EmbedPython.exe' failed
CMakeFiles\Makefile2:66: recipe for target 'CMakeFiles/EmbedPython.dir/all' failed
CMakeFiles\Makefile2:78: recipe for target 'CMakeFiles/EmbedPython.dir/rule' failed
Makefile:117: recipe for target 'EmbedPython' failed
Not sure what to do to make the project run.Any help would be appreciated.
EDIT:
the result from make VERBOSE=1
D:\Projects\EmbedPython\cmake-build-debug>make VERBOSE=1
"C:\Program Files\JetBrains\CLion 172.2273.4\bin\cmake\bin\cmake.exe" -HD:\Projects\EmbedPython -BD:\Projects\EmbedPython\cmake-build-debug --check-build-system CMakeFiles\Makefile.cmake 0
"C:\Program Files\JetBrains\CLion 172.2273.4\bin\cmake\bin\cmake.exe" -E cmake_progress_start D:\Projects\EmbedPython\cmake-build-debug\CMakeFiles D:\Projects\EmbedPython\cmake-build-debug\CMakeFiles\progress.marks
make -f CMakeFiles\Makefile2 all
make[1]: Entering directory 'D:/Projects/EmbedPython/cmake-build-debug'
make -f CMakeFiles\EmbedPython.dir\build.make CMakeFiles/EmbedPython.dir/depend
make[2]: Entering directory 'D:/Projects/EmbedPython/cmake-build-debug'
"C:\Program Files\JetBrains\CLion 172.2273.4\bin\cmake\bin\cmake.exe" -E cmake_depends "MinGW Makefiles" D:\Projects\EmbedPython D:\Projects\EmbedPython D:\Projects\EmbedPython\cmake-build-debug D:\Projects\EmbedPython\cmake-build-debug D:\Projects\EmbedPython\cmake-build-debug\CMakeFiles\EmbedPython.dir\DependInfo.cmake --color=
make[2]: Leaving directory 'D:/Projects/EmbedPython/cmake-build-debug'
make -f CMakeFiles\EmbedPython.dir\build.make CMakeFiles/EmbedPython.dir/build
make[2]: Entering directory 'D:/Projects/EmbedPython/cmake-build-debug'
[ 50%] Linking CXX executable EmbedPython.exe
"C:\Program Files\JetBrains\CLion 172.2273.4\bin\cmake\bin\cmake.exe" -E cmake_link_script CMakeFiles\EmbedPython.dir\link.txt --verbose=1
"C:\Program Files\JetBrains\CLion 172.2273.4\bin\cmake\bin\cmake.exe" -E remove -f CMakeFiles\EmbedPython.dir/objects.a
C:\PROGRA~2\MINGW-~1\I686-6~1.0-P\mingw32\bin\ar.exe cr CMakeFiles\EmbedPython.dir/objects.a #CMakeFiles\EmbedPython.dir\objects1.rsp
C:\PROGRA~2\MINGW-~1\I686-6~1.0-P\mingw32\bin\G__~1.EXE -g -Wl,--whole-archive CMakeFiles\EmbedPython.dir/objects.a -Wl,--no-whole-archive -o EmbedPython.exe -Wl,--out-implib,libEmbedPython.dll.a -Wl,--major-image-version,0,--minor-image-version,0 #CMakeFiles\EmbedPython.dir\linklibs.rsp
CMakeFiles\EmbedPython.dir/objects.a(main.cpp.obj): In function `main':
D:/Projects/EmbedPython/main.cpp:16: undefined reference to `_imp__Py_Initialize'
D:/Projects/EmbedPython/main.cpp:17: undefined reference to `_imp__PyUnicode_DecodeFSDefault'
D:/Projects/EmbedPython/main.cpp:20: undefined reference to `_imp__PyImport_Import'
D:/Projects/EmbedPython/main.cpp:24: undefined reference to `_imp__PyObject_GetAttrString'
D:/Projects/EmbedPython/main.cpp:27: undefined reference to `_imp__PyCallable_Check'
D:/Projects/EmbedPython/main.cpp:28: undefined reference to `_imp__PyTuple_New'
D:/Projects/EmbedPython/main.cpp:30: undefined reference to `_imp__PyLong_FromLong'
D:/Projects/EmbedPython/main.cpp:38: undefined reference to `_imp__PyTuple_SetItem'
D:/Projects/EmbedPython/main.cpp:40: undefined reference to `_imp__PyObject_CallObject'
D:/Projects/EmbedPython/main.cpp:43: undefined reference to `_imp__PyLong_AsLong'
D:/Projects/EmbedPython/main.cpp:49: undefined reference to `_imp__PyErr_Print'
D:/Projects/EmbedPython/main.cpp:55: undefined reference to `_imp__PyErr_Occurred'
D:/Projects/EmbedPython/main.cpp:56: undefined reference to `_imp__PyErr_Print'
D:/Projects/EmbedPython/main.cpp:63: undefined reference to `_imp__PyErr_Print'
D:/Projects/EmbedPython/main.cpp:67: undefined reference to `_imp__Py_FinalizeEx'
collect2.exe: error: ld returned 1 exit status
CMakeFiles\EmbedPython.dir\build.make:97: recipe for target 'EmbedPython.exe' failed
make[2]: *** [EmbedPython.exe] Error 1
make[2]: Leaving directory 'D:/Projects/EmbedPython/cmake-build-debug'
CMakeFiles\Makefile2:66: recipe for target 'CMakeFiles/EmbedPython.dir/all' failed
make[1]: *** [CMakeFiles/EmbedPython.dir/all] Error 2
make[1]: Leaving directory 'D:/Projects/EmbedPython/cmake-build-debug'
Makefile:82: recipe for target 'all' failed
make: *** [all] Error 2

I had the exactly same problem, just with Python 3.7 while trying to build the example from the Python manual.
My system is a 64-bit Windows, the installed Python is a 64-bit 3.7 (from Anaconda3), and the compiler is a 32-bit MinGW 5.3.0 (from Qt 5.11).
The simplest solution that worked for me is the following:
Download Windows x86 embeddable zip file from this page.
Put the content of that archive to a folder inside the project you're building.
Do not install anything from that archive and do not put it on the system PATH.
Add the above folder to the gcc library search path, using: -L"path/to/folder/"
Add the python library to the linker, using -l"python37" ( replace 37 with whatever version you download)
As noted here (this was a hard one to find!), add a definition, using -DPy_BUILD_CORE_BUILTIN=1 (It is also possible to write #define DPy_BUILD_CORE_BUILTIN 1 just before #include-ing the Python header, though I would not recommend it)
Provide the path to the Python headers, using -I"path/to/include". I used the one from Anaconda, e.g. -I"c:/Users/user/Anaconda3/include/". Any installed header will do, just make sure its from the same version (headers from an older version might also be used, but this may cause a rupture in the space-time continuum)
Make sure that #include <Python.h> is before any other include, as stated in the manual.
As a side note, the MinGW linker (ld) is perfectly content, for many years now, if you just give it the "dll" file. No "lib", nor "a", is needed if you don't have one and only perform dynamic linking. This is why I just told the linker to use python37.
It it actually smart enough to look for files like python37.lib, python37.dll & libpython37.a.
Also note that the "embedable zip" is just the bare minimum needed for, well, embedding Python.
And as a last comment, contrary to what is stated here, there is no problem whatsoever linking from GCC with a library compiled using MSVS (and vice versa), as long as the library uses the plain C interface, since that interface is pretty much the only thing that is compatible across different compilers for any given platform.
This is pretty much the exact reason why Python is using the C interface (and nothing else, not even C++) for extending & embedding - to allow code written in any language, using any tool set, to interface with Python.

I had the same problem.
probably the problem is because of using 32 bit MinGW and 64 bit Python. you should install 32 bit version of python
Hope it will be useful to you :-)

Undefined Reference to "gsl_rng_unform", "gsl_rng_mt19937", "gsl_rng_alloc", "gsl_rng_set"

I am trying to compile a pyx code to obtain a pyd/dll file for python on my Windows 64 machine. I am doing it step by step in the command window to figure out where it is going wrong.
I successfully converted the pyx into a c file called samplers.c. Then into a .o file. I am at the last step I believe in compiling a shared object (pyd), but for some reason the compiler cannot read what is inside the gsl_rng.h file. It is clearly included as one of the directories in the gsl library, but for some reason cannot find them and throws the undefined reference error. I've even included -lgsl -lgslcblas -lm as a lot of forum posts suggest, but still no dice.
c:\Users\MyName\Anaconda\conda-bld\work>C:\TDM-GCC-64\bin\gcc.exe -DMS_WIN64 -shared -s samplers.o build\temp.win-amd64-2.7\Release\samplers.def -LC:\Users\MyName\Anaconda\gsl\lib -LC:\Users\MyName\Anaconda\libs -LC:\Users\MyName\Anaconda\PCbuild\amd64-lgsl -lgslcblas -lm -lpython27 -lmsvcr90 -o c:\Users\MyName\Anaconda\conda-bld\work\samplers.pyd
samplers.o:samplers.c:(.text+0x1f73): undefined reference to `gsl_rng_uniform'
samplers.o:samplers.c:(.text+0x20a91): undefined reference to `gsl_rng_mt19937'
samplers.o:samplers.c:(.text+0x20a96): undefined reference to `gsl_rng_alloc'
samplers.o:samplers.c:(.text+0x20c75): undefined reference to `gsl_rng_set'
c:/tdm-gcc-64/bin/../lib/gcc/x86_64-w64-mingw32/4.8.1/../../../../x86_64-w64-mingw /bin/ld.exe: samplers.o: bad reloc address 0x0 in section `.data'
collect2.exe: error: ld returned 1 exit status

... -LC:\Users\MyName\Anaconda\PCbuild\amd64-lgsl ...
Individual arguments to a command must be separated by a space, in this case the -L and -l arguments.

How can I build my C extensions with MinGW-w64 in Python?

So I have a few Python C extensions I have previously built for and used in 32 bit Python running in Win7. I have now however switched to 64 bit Python, and I am having issues building the C extension with MinGW-w64.
I made the changes to distutils as per this post, but I am getting some weird errors suggesting something is wrong:
$ python setup.py build
running build
running build_ext
building 'MyLib' extension
c:\MinGW64\bin\x86_64-w64-mingw32-gcc.exe -mdll -O -Wall -Ic:\Python27\lib\site-packages\numpy\core\include -Ic:\Python27\include -Ic:\Python27\PC -c MyLib.c -o build\temp.win-amd64-2.7\Release\mylib.o
MyLib.c: In function 'initMyLib':
MyLib.c:631:5: warning: implicit declaration of function 'Py_InitModule4_64' [-Wimplicit-function-declaration]
writing build\temp.win-amd64-2.7\Release\MyLib.def
c:\MinGW64\bin\x86_64-w64-mingw32-gcc.exe -shared -s build\temp.win-amd64-2.7\Release\mylib.o build\temp.win-amd64-2.7\Release\MyLib.def -Lc:\Python27\libs -Lc:\Python27\PCbuild\amd64 -lpython27 -o build\lib.win-amd64-2.7\MyLib.pyd
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x13d): undefined reference to `__imp_PyExc_ValueError'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x1275): undefined reference to `__imp_PyExc_ValueError'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x1eef): undefined reference to `__imp_PyExc_ImportError'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x1f38): undefined reference to `__imp_PyExc_AttributeError'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x1f4d): undefined reference to `__imp_PyCObject_Type'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x1f61): undefined reference to `__imp_PyExc_RuntimeError'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x1fc7): undefined reference to `__imp_PyExc_RuntimeError'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x1ffe): undefined reference to `__imp_PyExc_RuntimeError'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x2042): undefined reference to `__imp_PyExc_RuntimeError'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x206c): undefined reference to `__imp_PyExc_RuntimeError'
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x208a): more undefined references to `__imp_PyExc_RuntimeError' follow
build\temp.win-amd64-2.7\Release\mylib.o:MyLib.c:(.text+0x20a7): undefined reference to `__imp_PyExc_ImportError'
collect2.exe: error: ld returned 1 exit status
error: command 'x86_64-w64-mingw32-gcc' failed with exit status 1
I have googled around quite a bit to find information, but it's not easy to find a definite answer. Could someone shed some light on this? What further changes should I do to be able to successfully build C extensions for 64 bit Python in Win7?
EDIT:
After some helpful pointers in cgohlke's comments below I managed to generate libpython27.a. However after following the advice on this post (2nd to last) I still had a the __imp_Py_InitModule4_64 error. After some serious Google-fu I managed to trip over this post telling me to rename the Py_InitModule4 line to Py_InitModule4_64. After that everything worked swimmingly.

This worked for me with Python 3.3 :
create static python lib from dll
python dll is usually in C:/Windows/System32; in msys shell:
gendef.exe python33.dll
dlltool.exe --dllname python33.dll --def python33.def --output-lib libpython33.a
mv libpython33.a C:/Python33/libs
use swig to generate wrappers
e.g., swig -c++ -python myExtension.i
wrapper MUST be compiled with MS_WIN64, or your computer will crash when you import the class in Python
g++ -c myExtension.cpp -I/other/includes
g++ -DMS_WIN64 -c myExtension_wrap.cxx -IC:/Python33/include
shared library
g++ -shared -o _myExtension.pyd myExtension.o myExtension_wrap.o -lPython33 -lOtherSharedLibs -LC:/Python33/libs -LC:/path/to/other/shared/libs
make sure all shared libs (gdal, OtherSharedLibs) are in your PATH
(windows does not use LD_LIBRARY_PATH or PYTHONPATH)
in Python, just: import myExtension
voila!

I realize this is an old question, but it is still the top search result. Today, in 2019, I was able to do this:
https://github.com/PetterS/quickjs/commit/67bc2428b8c0716538b4583f4f2b0a2a5a49106c
In short:
Make sure a 64-bit version of mingw-w64 is in the PATH.
Monkey-patch distutils:
import distutils.cygwinccompiler
distutils.cygwinccompiler.get_msvcr = lambda: []
Some differences in the shell w.r.t. escaping.
extra_link_args = ["-Wl,-Bstatic", "-lpthread"] in order to link statically and not have extra runtime deps.
pipenv run python setup.py build -c mingw32 now works.

Here is a example code for VC++ Build Tools
https://github.com/starnight/python-c-extension/tree/master/00-HelloWorld
You could try:
python setup.py -c mingw32
However this is not work for me.
My Solution is:
install Anaconda 64bit python 3.6
install mingw64
add mingw64/bin to PATH
compile dll from c file by
gcc -c libmypy.c -IC:\Users\{user_name}\Anaconda3\pkgs\python-3.6.4-h6538335_1\include
gcc -shared -o libmypy.dll libmypy.o -LC:\Users\{user_name}\Anaconda3\pkgs\python-3.6.4-h6538335_1\libs -lPython36
load dll file in .py script
from ctypes import *
m = cdll.LoadLibrary(r"C:\{path_to_dll}\libmypy.dll")
print(m.hello())

I created a monkey-patch for setuptools to let you to build_ext with mingw64 on Windows easily. See https://github.com/imba-tjd/mingw64ccompiler

I used this thread to wade through learning how to make a C extension, and since most of what I learned is in it, I thought I'd put the final discovery here too, so that someone else can find it if they are looking.
I wasn't trying to compile something big, just the example in Hetland's Beginning Python. Here is what I did (the example C pgm is called palindrome.c). I'm using Anaconda with python 3.7 in it, and the TDM-GCC version of MinGW64. I put all of the tools used into my Path, and all of the paths needed in PYTHONPATH, and the ..\Anaconda3 directory into PYTHON_HOME. I still ended up using explicit paths on some things.
I created the libpython37.a library with gendef.exe and dlltool.exe as Mark said above, and put it in ..\Anaconda3\libs.
I followed the prescription in Hetland:
gcc -c palindrome.c
gcc -I$PYTHON_HOME -I$PYTHON_HOME/Include -c palindrome_wrap.c
The second failed, the compiler couldn't find Python.h, the following worked:
gcc -I[somedirectories]\Anaconda3\Include -c palindrome_wrap.c
I then did, as many have said, including Hetland 3rd ed.,
gcc -shared palindrome.o palindrome_wrap.o [somedirectories]/Anaconda3/libs/libpython37.a -o _palindrome.dll
This did not work. Even with the Load Library cswu used (which I found elsewhere, too).
So I gendef'd _palindrome.dll and couldn't find the function in it, "is_palindrome" in the exports. I went through some of the SWIG documentation, and declared the function both in the %{ %} section and below it, both extern, that finally got the function extern'd in palindrome_wrap.c as it should have been. But no export, so I went back into palindrome.c and redeclared the function as:
declspec(dllexport) extern int __stdcall is_palindrome(char* text)
and redeclared it in palindrome.i in both places as above with this signature.
Partial success! It got listed in the Export section when I gendef'd _palindrome.dll and I could do cswu's call using Load Library. But still not do what Hetland says and do
import _palindrome
in Python.
Going back to all the sources again, I could not figure this out. I finally started reading the SWIG documentation from the beginning leaving no stone unturned -- Searching through the manual doesn't produce the place found.
At the end of Introduction Sec. 2.7 Incorporating Into a Build System, under the sample Make process, it says:
"The above example will generate native build files such as makefiles, nmake files and Visual Studio projects which will invoke SWIG and compile the generated C++ files into _example.so (UNIX) or _example.pyd (Windows). For other target languages on Windows a dll, instead of a .pyd file, is usually generated."
And that's the answer to the last problem:
The compile step for the dll should read:
gcc -shared palindrome.o palindrome_wrap.o [somedirectories]/Anaconda3/libs/libpython37.a -o _palindrome.pyd
(I didn't go back and change out my declspec declarations so I don't know whether they were necessary, so they were still there too).
I got a file, _palindrome.pyd
Which if in the PYTHONPATH (mine was local) works, and one can then do
import _palindrome
from _palindrome import is_palindrome
and use the exported, properly wrapped and packaged C function, compiled with TDM-GCC, in python as promised. gcc, which is MinGW64 in a different installation, knows how to do the .pyd file. I diffed the dll and pyd since they were the same byte length. They are not the same at hundreds of points.
Hope this helps someone else.