Warning when casting FARPROC from GetProcAddress to specific function pointer type in MinGW-w64

I am using MinGW-w64 and trying to dynamically import a function from a DLL using GetProcAddress. The function I want to import has the following signature:

__declspec(dllexport) double __cdecl func(double t, unsigned int n);

To retrieve the function, I am using GetProcAddress from WIN32 API as follows:

typedef double (__cdecl *TYPE_FUNCTION)(double, unsigned int);
TYPE_FUNCTION func_ptr = (TYPE_FUNCTION) GetProcAddress(hinstLib, "func");

However, I receive the following:

warning: cast between incompatible function types from 'FARPROC' {aka 'long long int (*)()'} to 'double (*)(double, unsigned int)'

Is this warning something I should be concerned about? If so, how can I safely cast or call the function? Would the cast cause any potential issues at runtime?

Solution

use

__declspec(dllimport) double __cdecl func(double t, unsigned int n);

and

PVOID __imp_func;

(in case c++ declare both as EXTERN_C or extern "C" )

and finally

__imp_func = GetProcAddress(hinstLib, "func");

so we not need any typedef and cast

explanation:

when we declare function func with __declspec(dllimport) attribute, compiler declare variable extern PVOID __imp_func; (add __imp_) prefix to decorated function func name. and when you call func compiler generate code call __imp_func; so all what we need - implement PVOID __imp_func;. in case static link - the __imp_func will be inside some lib file. if you use dynamic linking - simply implement PVOID __imp_func; by self (without extern) and assign it value from GetProcAddress (or LdrGetProcedureAddress). note - this is for x64 mangling.

for x86 this will be PVOID _imp__func (because __cdecl - func will be transformed to _func and variable x transformed to _x so PVOID _imp__func generate __imp__func symbol in x86)

if use __stdcall - will be PVOID _imp__func@12 (__imp__func@12 symbol). we can not declare PVOID _imp__func@12; already. but we can use asm for this. or if use CL (more known as msvc) compiler (latest versions) we can use

__identifier keyword with

#pragma warning(disable: 4483) // Allow use of __identifier

so code in case x86 and if api was __stdcall

#pragma warning(disable: 4483) // Allow use of __identifier

__declspec(dllimport) double __stdcall func(double t, unsigned int n);

#define __imp_func __identifier("_imp__func@12")

PVOID __imp_func; // = GetProcAddress(hinstLib, "func");