https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110848
--- Comment #6 from Aaron Ballman <aaron at aaronballman dot com> --- (In reply to Andrew Pinski from comment #4) > Maybe my issue is this has been a documented extension for 20 years now. Which is totally fair -- we don't usually enable congratulatory diagnostics by default. > -pedantic or -std=c++NN has always rejected it like it should. GCC has other > extensions which folks could use by accident too (like statement > expressions). Why is VLA special here? FWIW, I can't honestly say I've ever seen someone use a statement expression accidentally, though I believe it's possible to do so if you work hard enough at it. That said, I think misuse of accidental VLAs has more opportunity for poor security behavior (specifically around attacker-controllable stack usage) than for statement expressions. Given the security concerns coupled with the ease of accidental usage, I think VLAs *are* different than statement expressions. Some supporting evidence of the confusion in the wild: https://stackoverflow.com/questions/70912167/how-do-i-tell-if-i-am-using-vla-variable-length-array https://stackoverflow.com/questions/39334435/variable-length-array-vla-in-c-compilers https://ddanilov.me/default-non-standard-features/ https://meta.stackoverflow.com/questions/376955/what-should-i-do-when-an-op-uses-variable-length-arrays-vlas-in-c https://cplusplus.com/forum/beginner/284866/ (Granted, there's confusion about *everything* in C and C++.) It's worth noting that -std=c++NN does *not* reject use of VLAs; you have to pass -pedantic or -Wvla to get the diagnostic: https://godbolt.org/z/PGorTYG7r
