Fstream can't read or write files 4GB even with -m64?

Question

Using C++-style streams, I have been unable to read or write files >4GB. For example, when writing 5GB in one go, I get only 1GB. The header for write uses the type streamsize for the size parameter, and according to sizeof, streamsize is 8 bytes (when using -m64). Looking at the assembly for a simple testcase, I verified that size parameter was not truncated before calling the write function.
What makes this interesting is that I can read or write large files if I do it in the C-style (fopen, fwrite, fclose) or if I use the C++ functions and manually do it in 1GB blocks. I tried the instructions for LFS, but they didn't work and it seems like it shouldn't since this is C++ and I am building a 64-bit app. I have observed this with solaris studio 12.3 and 12.4.
Is this a bug or am I missing a compiler flag?
A simple testcase to expose this:
#include <iostream>
#include <fstream>
#include <stdio.h>
using namespace std;
int main() {
  streamsize goal_size = ((int64_t) 1<<32) + ((int64_t) 1<<30);
  cout << goal_size << endl;
  char* data = new char[goal_size];
  fill(data,data+goal_size,'c');
  FILE* f = fopen("classic.data","w");
  fwrite(data,1,goal_size,f);
  fclose(f);
  fstream file("stream.data", std::ios::out | std::ios::binary);
  file.write(data,goal_size);
  file.close();

Answer 1

Eh... sorry, didnt read the source close enough
I can reproduce your misbehavior when compiling "by default" (with default -library=Cstd).
It fails somewhat differently with Apache STL (-library=stdcxx4), which is kinda the modern version of Cstd.
It works fine when compiling with -library=stlport4, or -library=stdcpp (-std=c++11).
Looks like it is a deficiency of those particular STLs.
regards,
  Fedor.