SDL and zlib issue, cannot create valid rwops structure from zip - c++

Question

I have been trying to read a zip archive and load a png image from it, however i am getting not valid image format error from SDL_Image. Here is the code
#include <SDL\SDL.h>
#include <SDL\SDL_opengl.h>
#include <SDL\SDL_image.h>
#define ZLIB_WINAPI //to use zlibwapi dll
#include <zlib.h>
#include <zip.h> //minizip
#include <unzip.h> //minizip
#include <string>
SDL_RWops* readfromarchive(std::string archive, std::string filename)
{
unzFile data;
unz_file_info info;
Uint8* buffer = NULL;
SDL_RWops* rw = NULL;
data = unzOpen(archive.c_str());
unzLocateFile( data, filename.c_str(), 1 );
unzGetCurrentFileInfo( data, &info, NULL, 0, NULL, 0, NULL, 0 );
unzOpenCurrentFile( data );
buffer = (Uint8*)malloc(info.uncompressed_size);
unzReadCurrentFile( data, buffer, info.uncompressed_size );
rw = SDL_RWFromMem(buffer, info.uncompressed_size);
free(buffer);
unzClose(data);
return rw;
}
when i do this
Surf_Temp = IMG_Load_RW( readfromarchive(archive, filename) , 1);
I get the error IMG_Load_RW: %s Unsupported image format
Well, if load directly from the unzipped file it works using IMG_Load(), works when create a rwops structure through sdl and load too using
IMG_Load_RW(SDL_RWFromFile(filename.c_str(), "rb"), 1);
So the file format is fine, all zlib and minizip functions dont return any error, i check the info struct and the data is consistant with the file i am trying to load, so the error is somewhere in creating the rwops struct.

Answer 1

The problem is the following. You are using an RWOPs structure form SDL. In the given case you want to read from memory. But you delete the memory before your read it. The RWOPs structure will not copy the memory, it needs to remain valid until everything is read.
To solve the problem, pull the call to IMG_Load_RW before the call to free(buffer);