Especially hard to read if you don't use C++.  It took a little Googliing to figure out that jump in C++ is like jmp in assembly or goto in C or Basic.  I thought it was the actual name of a function.  I never found it, grepping and searching in editors.  pkgTagFile seems to be a type, like maybe a pointer to a stuct.  My guess is that it spends 90% of its time there just because it's called thousands of times.   Anyway the problem went away, Synaptic works fine now, perfectly usable.