fseek with SEEK_END returns a “Invalid argument” error to manage large data(7GB) with python x86 C extension lib on windows7 x64

Question

I've been trying to manage large binary data( 7GB ) within python x86 original extension library.
But fseek with SEEK_END doesn't work well.

I put _FILE_OFFSET_BITS 64 macro. I also tried fseeko64 , but it raises an error.
With Less than 2GB files or using SEEK_CUR, SEEK_SET it's works fine.

I've been stuck for a couple of days. Could anybody give me ideas?

#define _GNU_SOURCE
#define _LARGEFILE_SOURCE
#define _LARGEFILE64_SOURCE
#define _FILE_OFFSET_BITS 64
#include <Python.h>
#include "structmember.h"
#include <stdio.h>

static PyObject *
MyClass_load(MyClass* self, PyObject *args)
{
  const char* file_path;
  if (!PyArg_ParseTuple(args, "s",  &file_path))
    return NULL;

  self->fp = fopen(file_path ,"rb");
  if (self->fp == NULL) {
    PyErr_SetString(PyExc_IOError, "File does not exist.");
    return NULL;
  }
  off_t offset = 0;
  if(fseek(self->fp, offset, SEEK_END) != 0){
    printf("%s\n", strerror(errno)); // show "Invalid argument"
    PyErr_SetString(PyExc_IOError, "Seek failed.");
    return NULL;
  }

  Py_INCREF(Py_None);
  return Py_None;
}

Environment:

• Windows 7 x64
• Python 2.7 x86
• MinGW GCC

Answer 1

Using '_fseeki64' and '_ftelli64' like VC works perfectly. I know I'm still using gcc to compile c file to python c library file, but I don't know why I can use VC code in gcc. Anyway, problem was solved!