On Mar 14, 2005, Eric Christopher <[EMAIL PROTECTED]> wrote: >> > Now, I wouldn't object to hacking GCC to avoid cross-jumping calls to >> > abort. It's just that I don't think that the common GNU use of abort >> > serves the users. >> Agreed. And as someone suggested, rather than treating abort >> specially within GCC, I think we'd be better off with a function >> attribute which prevented cross jumping to any function with >> the attribute set.
> I think it makes sense to just not crossjump noreturn attribute > functions if we're going to do this. I think this is a slippery slope. Crossjumping calls to abort(), or even arbitrary noreturn functions, is just yet another technique of compiler optimization that makes debugging more difficult. Crossjumping calls to returning functions can be just as confusing if you're looking at a backtrace in a debugger, especially if a function gets called from lots of different functions that all get inlined into one that ends up being identified as the frame owner, and if they get cross-jumped, things get very confusing. Then, there's sibcalling, that can also contribute for more confusing backtraces. To sum up my point: I don't think avoiding crossjumping of calls to abort will address the underlying issue, which is that backtraces obtained from optimized programs may surprise people. Such avoidance will only paper over the issue, making the compiler behavior less consistent and thus even more confusing. If people want accurate stack traces, they shouldn't be using optimizations that can mess with backtraces. What we might want to do is provide an option to disable all such optimizations. -- Alexandre Oliva http://www.ic.unicamp.br/~oliva/ Red Hat Compiler Engineer [EMAIL PROTECTED], gcc.gnu.org} Free Software Evangelist [EMAIL PROTECTED], gnu.org}
