Suuuny, png_longjmp function is called by a set of png_error functions. You are to trace through the PNG library to find out what code called png_error and then, eventually, png_longjmp. It seems that you will see the string explaining your case, i.e.
Suuuny, It does not really matter where you put this library. You must add a proper path to IAR compiler to be able to compile the library and code that uses it. Words "no definition for "GUI_PNG_Draw" are highly likely the linker swearings. It failed to…