Wframe-larger-than flag bug


I’m compiling my project with clang version 7.0.0-3.
I added compilation flag frame-larger-than in order to warning using more than 1024 bytes.

clang indeed warning as expected, but when I added -Werror in order to treat the warning as error clang ignore this flag and it stays warning.

the compilation flags include also save-temps=obj, when I remove this flag the warning treated as error.

Does save-temps flag should be related to -Werror or -Wframe-larger-than?

full compilation flags:
clang+±7 -D_SYS_LINUX_ -D_HOSTSYS_LINUX_ -D_CPU_ -D_SYS64_ -D_DEBUG_ -O2 -Wframe-larger-than=1024 -MD -Wall -save-temps=obj -Wextra -Wshadow -Werror -g -ggdb -fPIC


Works for me:

Thanks for your response.
I’ve opened your link and it’s seems that clang (trunk) is not handle the flag -save-temps=obj. compilation with -save-temps:
When changing the compiler to clang v0.8, same behaviour as describe before.
with flag -save-temps=obj:
without flag -save-temps=obj:


‫בתאריך שבת, 25 בינו׳ 2020 ב-8:16 מאת ‪David Blaikie‬‏ <‪‬‏>:‬

Ah, right, sorry I didn’t reproduce your steps exactly - thanks for highlighting the save-temps aspect.

Yeah, testing this with clang trunk (which, on godbolt, is built with assertions enabled) this crashes the compiler. Something about frame-larger-than doesn’t work with save-temps, which doesn’t super surprise me, -Wframe-larger-than with -fsyntax-only doesn’t produce any warning (frame-larger-than is implemented in the code generation pipeline, as much as we try to avoid doing that for warnings in clang, this one’s an exception).


‫בתאריך יום א׳, 26 בינו׳ 2020 ב-5:56 מאת ‪David Blaikie‬‏ <‪‬‏>:‬

Just to clarify, I cannot use flags -Wframe-larger-than, -Werror and -save-temps=obj and get error instead of warning. right?

‫בתאריך יום א׳, 26 בינו׳ 2020 ב-8:35 מאת ‪Ohad Alali‬‏ <‪‬‏>:‬

Doesn’t look like it, no.

I wouldn’t recommend using -Wframe-larger-than and -save-temps (even without -Werror) really, since that seems to crash the compiler, there’s probably no great guarantees about what that’s doing.

Ok, thanks a lot for your help.

‫בתאריך יום א׳, 26 בינו׳ 2020 ב-8:42 מאת ‪David Blaikie‬‏ <‪‬‏>:‬