Name mangling different between 32bit and 64bit Linux machines

[A Former User]

I compiled Qt on a 64bit Linux machine
one time using: linux-g++-32
and the second time: linux-g++-64

In the 32 bit version I got png_create_info_struct
and all other png_ functions were C mangled
and in the 64 bit version I got png_create_info_struct@@PNG12_0
and all other png_ functions were C++ mangled

I got the information using nm -s

This caused other problems since I use freeimage library. What can cause this name mangling difference?