Segher Boessenkool <seg...@kernel.crashing.org> writes: > On Mon, Jul 02, 2018 at 11:33:32AM +1000, Michael Ellerman wrote: >> What if we write it: >> >> char saved_0x500[0x600 - 0x500]; >> >> Hopefully the compiler is smart enough not to generate a VLA for that :) > > It is a VLA if the array size is not an integer constant expression. This > is defined by C; the compiler has nothing to do with it. 0x600-0x500 is > an integer constant expression, so this is not a VLA.
Thanks. That wasn't meant as a dig at GCC. Kees had an epic struggle with the kernel's min/max() macros which were causing expressions that looked like they should be constant to generate VLAs. > But if you meant if GCC will ever do a dynamic stack allocation for a fixed > size local variable: yes indeed, I hope not! Hey that would be cool, just-in-time local variable allocation :) cheers
