error LNK2019: unresolved external symbol ___iob_func referenced in function "void __cdecl Padding(int)"

Question

Using the FTDI API compiles and links fine under Visual Studio 2012.

but under VS 2014, it gives:

Error LNK2019: unresolved external symbol ___iob_func referenced in function "void __cdecl Padding(int)"

Have the standard libraries changed?

Answer 1

Yes, the standard libraries have changed, and FTDI doesn't seem to care - at least not as of CDM2.12.18 driver version.

The problem is described in the answers to this question.

The void __cdecl Padding(int) function from devcon.obj within ftd2xx.lib is the culprit. It references one of stdin, stdout or stderr, given as macros. The contents of these macros changed.

Since we don't really expect any I/O from the FTDI library, we might as well provide the simplest implementation possible:

FILE* __cdecl _imp____iob_func() { return 0; }

If you want a version that does what it's supposed to do:

FILE* __cdecl _imp____iob_func()
{
    struct _iobuf_VS2012 { // ...\Microsoft Visual Studio 11.0\VC\include\stdio.h #56
        char *_ptr;
        int   _cnt;
        char *_base;
        int   _flag;
        int   _file;
        int   _charbuf;
        int   _bufsiz;
        char *_tmpfname; };
    // VS2015 has FILE = struct {void* _Placeholder}

    static struct _iobuf_VS2012 bufs[3];
    static char initialized = 0;

    if (!initialized) {
        bufs[0]._ptr = stdin->_Placeholder;
        bufs[1]._ptr = stdout->_Placeholder;
        bufs[2]._ptr = stderr->_Placeholder;
        initialized = 1;
    }

    return (FILE*)&bufs;
}