diff options
| author | Rikard Falkeborn <[email protected]> | 2021-05-22 17:42:02 -0700 |
|---|---|---|
| committer | Linus Torvalds <[email protected]> | 2021-05-22 15:09:07 -1000 |
| commit | f747e6667ebb2ffb8133486c9cd19800d72b0d98 (patch) | |
| tree | da4178160dfb6592c2a37f9eed45b391b5a47e9f /tools/include/linux | |
| parent | 0f90b88dbcd1143e0f408502eba0af97429c502a (diff) | |
linux/bits.h: fix compilation error with GENMASK
GENMASK() has an input check which uses __builtin_choose_expr() to
enable a compile time sanity check of its inputs if they are known at
compile time.
However, it turns out that __builtin_constant_p() does not always return
a compile time constant [0]. It was thought this problem was fixed with
gcc 4.9 [1], but apparently this is not the case [2].
Switch to use __is_constexpr() instead which always returns a compile time
constant, regardless of its inputs.
Link: https://lore.kernel.org/lkml/[email protected] [0]
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19449 [1]
Link: https://lore.kernel.org/lkml/[email protected] [2]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Rikard Falkeborn <[email protected]>
Reported-by: Tetsuo Handa <[email protected]>
Acked-by: Arnd Bergmann <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Yury Norov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Diffstat (limited to 'tools/include/linux')
| -rw-r--r-- | tools/include/linux/bits.h | 2 | ||||
| -rw-r--r-- | tools/include/linux/const.h | 8 |
2 files changed, 9 insertions, 1 deletions
diff --git a/tools/include/linux/bits.h b/tools/include/linux/bits.h index 7f475d59a097..87d112650dfb 100644 --- a/tools/include/linux/bits.h +++ b/tools/include/linux/bits.h @@ -22,7 +22,7 @@ #include <linux/build_bug.h> #define GENMASK_INPUT_CHECK(h, l) \ (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ - __builtin_constant_p((l) > (h)), (l) > (h), 0))) + __is_constexpr((l) > (h)), (l) > (h), 0))) #else /* * BUILD_BUG_ON_ZERO is not available in h files included from asm files, diff --git a/tools/include/linux/const.h b/tools/include/linux/const.h index 81b8aae5a855..435ddd72d2c4 100644 --- a/tools/include/linux/const.h +++ b/tools/include/linux/const.h @@ -3,4 +3,12 @@ #include <vdso/const.h> +/* + * This returns a constant expression while determining if an argument is + * a constant expression, most importantly without evaluating the argument. + * Glory to Martin Uecker <[email protected]> + */ +#define __is_constexpr(x) \ + (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) + #endif /* _LINUX_CONST_H */ |