Messages in this thread Patch in this message | | | From | David Laight <> | Subject | [PATCH v3 5/5] minmax: Relax check to allow comparison between int and small unsigned constants. | Date | Fri, 4 Aug 2023 10:56:21 +0000 |
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Convert constants between 0 and INT_MAX to 'int' prior to comparisons so that min(signed_var, 20u) and, more commonly, min(signed_var, sizeof()) are both valid.
Signed-off-by: David Laight <david.laight@aculab.com> --- v3: Fix compiler warnings for 'x >= 0' with unsigned/pointer types. v2: Add cast to fix min/max with pointer types. include/linux/minmax.h | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-)
diff --git a/include/linux/minmax.h b/include/linux/minmax.h index f56611ab486a..8d292aa55f5f 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -8,11 +8,13 @@ /* * min()/max()/clamp() macros must accomplish three things: * - * - avoid multiple evaluations of the arguments (so side-effects like + * - Avoid multiple evaluations of the arguments (so side-effects like * "x++" happen only once) when non-constant. - * - perform signed v unsigned type-checking (to generate compile + * - Perform signed v unsigned type-checking (to generate compile * errors instead of nasty runtime surprises). - * - retain result as a constant expressions when called with only + * Constants from 0 to INT_MAX are cast to (int) so can be used + * in comparisons with signed types. + * - Retain result as a constant expressions when called with only * constant expressions (to avoid tripping VLA warnings in stack * allocation usage). */ @@ -24,9 +26,17 @@ __builtin_choose_expr(__is_constexpr(is_signed_type(typeof(x))), \ is_signed_type(typeof(x)), 0) -#define __types_ok(x, y) \ - (__is_signed(x) == __is_signed(y) || \ - __is_signed((x) + 0) == __is_signed((y) + 0)) +#define __is_noneg_int(x) \ + (__builtin_choose_expr(!__is_constexpr(x), false, \ + __builtin_choose_expr(__is_signed(x), x, 0) >= 0 && \ + (x) <= (typeof((x) + 0))(long)__INT_MAX__)) + +#define __int_const(x) __builtin_choose_expr(__is_noneg_int(x), (int)(long)(x), (x)) + +#define __types_ok(x, y) \ + (__is_signed(x) == __is_signed(y) || \ + __is_signed((x) + 0) == __is_signed((y) + 0) || \ + __is_noneg_int(x) || __is_noneg_int(y)) #define __cmp_op_min < #define __cmp_op_max > @@ -34,24 +44,24 @@ #define __cmp(op, x, y) ((x) __cmp_op_##op (y) ? (x) : (y)) #define __cmp_once(op, x, y, unique_x, unique_y) ({ \ - typeof(x) unique_x = (x); \ - typeof(y) unique_y = (y); \ + typeof(__int_const(x)) unique_x = (x); \ + typeof(__int_const(y)) unique_y = (y); \ static_assert(__types_ok(x, y), \ #op "(" #x ", " #y ") signedness error, fix types or consider " #op "_unsigned() before " #op "_t()"); \ __cmp(op, unique_x, unique_y); }) #define __careful_cmp(op, x, y) \ __builtin_choose_expr(__is_constexpr((x) - (y)), \ - __cmp(op, x, y), \ + __cmp(op, __int_const(x), __int_const(y)), \ __cmp_once(op, x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y))) #define __clamp(val, lo, hi) \ ((val) >= (hi) ? (hi) : ((val) <= (lo) ? (lo) : (val))) #define __clamp_once(val, lo, hi, unique_val, unique_lo, unique_hi) ({ \ - typeof(val) unique_val = (val); \ - typeof(lo) unique_lo = (lo); \ - typeof(hi) unique_hi = (hi); \ + typeof(__int_const(val)) unique_val = (val); \ + typeof(__int_const(lo)) unique_lo = (lo); \ + typeof(__int_const(hi)) unique_hi = (hi); \ static_assert(__builtin_choose_expr(__is_constexpr((lo) > (hi)), \ (lo) <= (hi), true), \ "clamp() low limit " #lo " greater than high limit " #hi); \ -- 2.17.1 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
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