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[01/10] compiler.h: add statically_false()

Message ID 20241203-is_constexpr-refactor-v1-1-4e4cbaecc216@wanadoo.fr (mailing list archive)
State New
Headers show
Series compiler.h: refactor __is_constexpr() into is_const{,_true,_false}() | expand

Commit Message

Vincent Mailhol via B4 Relay Dec. 2, 2024, 5:33 p.m. UTC 
From: Vincent Mailhol <mailhol.vincent@wanadoo.fr>

For completion, add statically_false() which is the equivalent of
statically_true() except that it will return true only if the input is
known to be false at compile time.

The == operator is used instead of the ! negation to prevent a
-Wint-in-bool-context compiler warning when the argument is not a
boolean. For example:

  statically_false(var * 0)

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
---
 include/linux/compiler.h | 1 +
 1 file changed, 1 insertion(+)
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Patch

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 469a64dd6495fefab2c85ffc279568a657b72660..a2a56a50dd85227a4fdc62236a2710ca37c5ba52 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -314,6 +314,7 @@  static inline void *offset_to_ptr(const int *off)
  * values to determine that the condition is statically true.
  */
 #define statically_true(x) (__builtin_constant_p(x) && (x))
+#define statically_false(x) (__builtin_constant_p(x) && (x) == 0)
 
 /*
  * This is needed in functions which generate the stack canary, see