On Mon, Jul 24, 2023, at 20:13, Arnd Bergmann wrote: >>> One difference between gcc and clang is that gcc tries to >>> be smart about warnings by using information from inlining >>> to produce better warnings, while clang never uses information >>> across function boundaries for generated warnings, so it won't >>> find this one, but also would ignore an unconditional use >>> of the uninitialized variable. >>> >>> >> If we have to change the kernel, what about the change below? >>> > >>> > To workaround the compiler bug we can simply init flag=0 to silence >>> > the warn, but even that is silly. Passing flag=0 into irqrestore is buggy. >>> >>> Maybe inc_active() could return the flags instead of modifying >>> the stack variable? that would also result in slightly better >>> code when it's not inlined. >> >> Which gcc are we talking about here that is so buggy? > > I think I only tried versions 8 through 13 for this one, but > can check others as well. I have a minimized test case at https://godbolt.org/z/hK4ev17fv that shows the problem happening with all versions of gcc (4.1 through 14.0) if I force the dec_active() function to be inline and force inc_active() to be non-inline. With clang, I only see the warning if I turn dec_active() into a macro instead of an inline function. This is the expected behavior in clang. Arnd
