On Wed, Dec 12, 2018 at 1:30 AM Andy Gibbs <andyg1...@hotmail.co.uk> wrote:
> On 10 December 2018 18:17, David Blaikie wrote: > > Possible that the online one isn't built with assertions enabled (you > could test this with other known crashers to see if they reproduce on > godbolt with assertion crash dumps or only with raw segfaults)? If that's > the case,t hen it's possible that the codepath that should assert continues > on and perhaps either has unexpected or even undefined behavior but not a > crash. > > Yes, it seems this is right. I have done a number of further tests and it > seems that the godbolt compilers are built without asserts. > > This, however, is a possible problem generally, isn't it? I build my > compilers always with release-asserts but I would guess it common that > compiler builds are simply release builds. And this means, if there is a > bug in the compiler, it may generate invalid code with no warning at all > (my bug report gives an example of this) where in fact, if it were built > with asserts then the bug would have been made visible (and maybe fixed!). > > I know there can always be bugs which still act invisibly, but given that > clang is good at sticking asserts everywhere in its code :o) isn't it worth > ensuring asserts are always enabled? i.e. build 'release-asserts' even > when asked to do a release build? > Assertions are expensive (at one point the LLVM build system had a warning about builds with assertions enabled, that they may be 10x slower than without assertions) - so it's not practical for most folks to run with them enabled for all their builds. - Dave > > Cheers, > Andy >
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