On 3/6/21 12:03 PM, Alexander Motzkau via Gcc-help wrote: > Andrew Haley wrote: >> The compiler is telling you that it's assuming that expbuf + 120 >> does not wrap around. There's nothing really mysterious about it. > > But should that warning only occur on -Wstrict-overflow=3 or higher? > Why does it occur on -Wstrict-overflow=2? -Wstrict-overflow=2 triggers when GCC encounters expressions that reduce to a constant, where that evaluation depends on overflow not occuring. In this case the expression is expbuf + 120 > get_buf() This exact phrase doesn't occur in your program, but GCC generates it while optimizing. > I usually compile my software with -Werror (so that warnings won't be > ignored anymore) and so this information from the compiler broke the build > when going from GCC 8 to GCC 9. It seems -Wstrict-overflow=2 there is not > fit to be used with -Werror anymore. Am I correct? I doubt that it ever was. -Wstrict-overflow=2 is informative, for the programmer. It doesn't suggest that anything is questionable about the program, and in this case it's difficult or impossible to avoid. Re upgrading: over time, GCC gets better and better at diagnosing and providing information. This inevitably means that programmers using -Werror with high levels of warnings have to change their programs when a new GCC is used. -- Andrew Haley (he/him) Java Platform Lead Engineer Red Hat UK Ltd. <https://www.redhat.com> https://keybase.io/andrewhaley EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671
