ld --wrap and zcat

[Shaun Jackman]

fstream::open in libstdc++ calls fopen in libc. I'd like to use ld 
--wrap to hook the fopen call to call popen to decompress a .gz file 
using zcat. Is this possible with ld --wrap? From my experimentation, 
it seems not. Is this possible using LD_PRELOAD and dlsym?

Thanks,
Shaun