Use 32bit shared library from 64bit application? - c

Question

I have created a simple linux 32bit shared library(.so) for my rendering wrappers but i've hit a wall when i figured that i can only
use them through 32bit applications....................
This is how my code looks like:
RendIFace.h:
//Basic renderer interface
struct Renderer
{
int type;
...other things
};
GLRend.c:
#include "RendIFace.h"
struct Renderer* GLRendererCreate(int width,int height,int bytesPerPixel)
{
struct Renderer* rend = (struct Renderer*)malloc(sizeof(Renderer));
rend->type = GLR;
..other things
return rend;
}
SDLRend.c:
#include "RendIFace.h"
struct Renderer* SDLRendererCreate(int width,int height,int bytesPerPixel)
{
struct Renderer* rend = (struct Renderer*)malloc(sizeof(Renderer));
rend->type = SDLR;
..other things
return rend;
}
And i compile both as shared 32bit libraries(.so) and load them through the main application...
But now there is a big problem.My libraries are all 32bit and return 32bit pointers which means that i can't use them through
an 64bit application without rebuilding all the library code base(!!!).
So i would like to ask more experienced people : How do i handle this issue ? Is it possible to use just a single shared library for both architectures ???

Answer 1

You must be consistent. A 64-bit application can only use 64-bit libraries and a 32-bit application can only use 32-bit libraries. Both work; either choice is fine, and it's possible to compile the same code for both systems.
If you go for 'all 32-bit', use:
gcc -m32
If you go for 'all 64-bit', use:
gcc -m64
Sometimes, I'll tell make that the C compiler is gcc -m32 (or -m64) rather than just gcc to ensure the right value is used everywhere.

Answer 2

You can't do what you're asking. You must compile both the final executable and any libraries (both static and shared) for the same architecture.
On GCC, this can be done easily by passing the command line argument -m32 either directly in the command line or by adding it CCFLAGS in your Makefile.
While it is possible to run x86 code on a x86_64 operating system (you just need to have all the right libraries and their respective recursive dependencies), you cannot, in one executable or in one address space, combine x86 and x86_64 binaries.