nathanchance added a comment. I took the most recent version for a spin against the Linux kernel. The couple of issues that a previous revision of the warning flagged (https://github.com/ClangBuiltLinux/linux/issues/1806, https://github.com/ClangBuiltLinux/linux/issues/1807) are no longer visible (that seems intentional because both of those came from macro expressions) but I see a new one along a similar line as those:
https://elixir.bootlin.com/linux/v6.5-rc2/source/drivers/gpu/drm/v3d/v3d_drv.h#L343 In file included from drivers/gpu/drm/v3d/v3d_bo.c:25: drivers/gpu/drm/v3d/v3d_drv.h:343:24: warning: use of logical '&&' with constant operand [-Wconstant-logical-operand] 343 | if (NSEC_PER_SEC % HZ && | ~~~~~~~~~~~~~~~~~ ^ drivers/gpu/drm/v3d/v3d_drv.h:343:24: note: use '&' for a bitwise operation 343 | if (NSEC_PER_SEC % HZ && | ^~ | & drivers/gpu/drm/v3d/v3d_drv.h:343:24: note: remove constant to silence this warning 1 warning generated. Another minimized example showing how the warning can trigger with different configurations: $ cat x.c #define A 1000 #define B 300 #define C 250 #define D 100 int bar(void); int baz(void); int foo(void) { if (A % B && bar()) // 1000 % 300 = 100, warning return -3; if (A % C && bar()) // 1000 % 250 = 0, no warning return -2; if (A % D && bar()) // 1000 % 100 = 0, no warning return -1; return baz(); } $ clang -Wall -fsyntax-only x.c x.c:11:12: warning: use of logical '&&' with constant operand [-Wconstant-logical-operand] 11 | if (A % B && bar()) | ~~~~~ ^ x.c:11:12: note: use '&' for a bitwise operation 11 | if (A % B && bar()) | ^~ | & x.c:11:12: note: remove constant to silence this warning 1 warning generated. I am sure we can send a patch making that a boolean expression (although it is duplicated in a few places it seems so multiple patches will be needed) but I figured I would report it just in case there was something that should be changed with the warning, since I see there was already some discussion around not warning for macros and this seems along a similar line. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D142609/new/ https://reviews.llvm.org/D142609 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
