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pythondllshared-librariesctypesbyref

Error in values passed byref calling a dll in python

I have to different dlls exporting this functions (one function each dll):

dll1:

DECLDIR void getFrameworkVersion(int* pMajor, int* pMinor, int* pBugfix);

dll2:

void __stdcall getFrameworkVersion(int* pMajor, int* pMinor, int* pBugfix);

Im importing both dlls in python with no errors, and calling them with no errors either. However I'm getting wrong values

dll1 = cdll.LoadLibrary('dll1')
dll2 = oledll.LoadLibrary('dll2')

pMajor = pMinor = pbugFix = c_int()

dll1.getASTFrameworkVersion.argtypes = [ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_int)]
#test.eval.restype = ctypes.c_double
dll1.getASTFrameworkVersion(byref(pMajor), byref(pMinor), byref(pbugFix))
astVersion = "AST Framework version: " + str(pMinor.value) + "."  + str(pbugFix.value) + "."  + str(pMajor.value)

dll2.getFrameworkVersion.argtypes = [ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_int)]
dll2.getFrameworkVersion(byref(pMajor), byref(pMinor), byref(pbugFix))
asfVersion = "ASF Framework version: " + str(pMinor.value) + "."  + str(pbugFix.value) + "."  + str(pMajor.value)

I'm getting this output:

    AST Framework version: 0.0.0
    ASF Framework version: 14.14.14
Solution

  • pMajor = pMinor = bugFix = c_int() is wrong: all three Python names are the same c_int instance, so will contain the same value! What you're doing is equivalent to the following code in C:

    int x;
getFrameworkVersion(&x, &x, &x);

    So the fact that you get 0.0.0 is probably because the real result would end in .0, which overwrites the previous two values.