[PATCH v3 0/2] add _statically_true() to simplify GENMASK_INPUT_CHECK()

[Vincent Mailhol]

The first patch introduces a new variant of statically_true() named
_statically_true() which rely on __is_constexpr() to produce a
constant expression result which can be used in BUILD_BUG_ON_ZERO()
and other macros which expect a constant expression as input.

The second patch applies this newly created _statically_true() to
GENMASK_INPUT_CHECK().


** Changelog **

v2 -> v3:

   - split the single patch into a series of two patches.

   - add explanation of why _statically_true() is needed in addition
     to the existing statically_true(). Explain the pros and cons of
     each.

   - use __builtin_choose_expr() in _statically_true(). The
     _statically_true() of the v2 works perfectly fine when used in
     conjunction with BUILD_BUG_ON_ZERO() but fails if used, for
     example, in arrays or in static_assert().

Link: https://lore.kernel.org/all/20241111164743.339117-2-mailhol.vincent@xxxxxxxxxx/

v1 -> v2:

   - introduce _statically_true(), taking inspiration from
     statically_true() as introduced in commit 22f546873149 ("minmax:
     improve macro expansion and type checking").

Link: https://lore.kernel.org/all/20240609073513.256179-1-mailhol.vincent@xxxxxxxxxx/

Vincent Mailhol (2):
  compiler.h: add _static_assert()
  linux/bits.h: simplify GENMASK_INPUT_CHECK()

 include/linux/bits.h     |  5 ++---
 include/linux/compiler.h | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 3 deletions(-)

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2.45.2