Why Does My C Function Called from Python via ctypes Return an Incorrect Value?

C Function Called from Python via ctypes Returns Incorrect Value

When calling a C function from Python using ctypes, it's crucial to correctly specify the argument and return types to ensure proper data conversion. Failure to do so can result in incorrect values being returned.

In your case, you have specified the return type of the power function as c_float, but you have not specified the argument types. The default type for arguments is c_int, so Python is assuming that the x argument is an integer, which is not the case.

To correct this, you should specify the argument types as c_float as well:

functions.power.argtypes = [c_float, c_int]

After making this change, you should obtain the expected output of 125.0 when calling the power function from Python.

Remember, both the argument and return types need to be specified explicitly to ensure that ctypes can correctly convert data between Python and C. Failing to specify or misspelling either of these types can result in undefined behavior and incorrect values being returned.

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