On Nov 12, 2007, Joe Buck <[EMAIL PROTECTED]> wrote: > consider dropping observable points where the states will not match.
We can't really do that. The line number mapping is from PC to line number, regardless of how far into the execution or earlier lines the code is. Omitting certain mappings from PC to line numbers would be wrong. The piece of the puzzle we're still missing is how to get debuggers clever enough to decide where to set a breakpoint. Nowadays, debuggers (at least those I'm familiar with) tend to set breakpoints at the lowest-numbered PC corresponding to a given source line number. While this is useful at times, at other times what you want is the lowest PC after all instructions corresponding to the previous line, because at that point you know all the state of the previous line should be stable and hopefully still observable. Or something along these lines. I don't have a complete solution for this problem. It's very far from trivial, and I don't see that debug information can carry enough information for the compiler to aid the debugger in selecting where to place breakpoints in this regard. -- Alexandre Oliva http://www.lsd.ic.unicamp.br/~oliva/ FSF Latin America Board Member http://www.fsfla.org/ Red Hat Compiler Engineer [EMAIL PROTECTED], gcc.gnu.org} Free Software Evangelist [EMAIL PROTECTED], gnu.org}
