undefined reference to _imp_* in MinWG - windows

Question

I want to compile a simple test project for a library that makes use of a ftd2xx driver. I already compiled it successfully on linux and I'm trying to do the same on Windows. The main difference are some minor modification to the library.
The test file I want to compile is this:
//#include "HPX-linux.h"
#include "HPX-Windows.h"
#include <stdlib.h>
#include <stdio.h>
int main(){
int devs;
getSerialNum(&devs);
printf("%d\n\n", devs);
simpleTest("./myTest/");
return 0;
}
And the preprocessing directives of HPX-Windows.h are as follows:
#ifndef HPXLINUX_H
#define HPXLINUX_H
#include <math.h>
#include <stdint.h>
#include <time.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include "ftd2xx.h"
#include <pthread.h>
// typedefs
//typedef uint16_t DWORD;
#ifndef __cplusplus
typedef uint8_t bool;
#endif
// static const defines
#ifndef __cplusplus
#define TRUE 1
#define FALSE 0
#endif
#define SUCCESS 0
#define FAILURE -1
#define RETRIEDTOOMANY -10
#define LOSTHEADFRAME -11
#define GOTAV 2
#ifdef __unix__
#define PRELIB extern
#elif _WIN32
#ifdef ADD_EXPORTS
#define PRELIB __declspec(dllexport)
#else
#define PRELIB __declspec(dllimport)
#endif
#endif
#ifdef __unix__
#define CALL
#elif _WIN32
#define CALL __cdecl
#endif
About ftd2xx, I have 2 .h headers, a .lib and a .dll.
With the driver properly installed, I could compile the library on linux with:
gcc -o test test.c -Wall -Wextra -lHPX-linux -lftd2xx -lm
I'm using MinGW on Windows. The command I'm using is:
gcc test.c HPX-Windows.c -L -lftd2xx -g
And then I get a list of errors type "undefined reference to _imp__*", being * a function. I expected them to be the functions of ftd2xx.h, but it also happens to function declared in HPX-Windows.h, including getSerialNum and simpleTest. Why does it happen when I'm using a .c source file instead of a library?

Answer 1

The error is caused by symbols exported with __declspec(dllimport) in header files that can't be imported from a shared library (.DLL).
I would recommend creating a libftd2xx.dll.a file from the ftd2xx.dll file and linking with that (e.g. if the files are in the current directory using -L. -lftd2xx.dll).
Or you could probably just link with the .dll file by specifying it in the gcc command, something like this: gcc -o test.exe test.c HPX-Windows.c ftd2xx.dll -g).
If that doesn't work check ftd2xx.h to see where __declspec(dllimport) is imported and see if you can set a define that causes the header to not use __declspec(dllexport)/__declspec(dllimport) and link with your lib file in case it's a static library (something like: gcc --static -o test.exe test.c HPX-Windows.c -L. -lftd2xx -g).