From 3f3dd44f1964c54b55e8c84343579bd7c1924df5 Mon Sep 17 00:00:00 2001
From: Eugene Syromyatnikov <evgsyr@gmail.com>
Date: Wed, 18 Aug 2021 21:49:12 +0200
Subject: [PATCH 148/150] macros: expand BIT macros, add MASK macros; add
 *_SAFE macros

These macros might make reading a code that often converts between powers
of 2 and values/masks a bit easier;  moreover, the *_SAFE versions should
help in cases where the shift values are expected to be equal to the type
bit width (which lead to UB otherwise).

Switching from BIT to BIT32 should also clarify bitness, which may be somewhat
murky at times (cf. printxval, printflags, and printxvals).

* src/macros.h [!BIT] (BIT): Rename to...
[!BIT32] (BIT32): ...this.
[!BIT64] (BIT64): New macro.
[!MASK32] (MASK32): Likewise.
[!MASK64] (MASK64): Likewise.
(BIT32_SAFE, BIT64_SAFE, MASK32_SAFE, MASK64_SAFE): New macros.
(FLAG): Use BIT32.
---
 src/macros.h | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/macros.h b/src/macros.h
index 467f5d0..2d7a83d 100644
--- a/src/macros.h
+++ b/src/macros.h
@@ -78,10 +78,34 @@ is_filled(const char *ptr, char fill, size_t size)
 # define IS_ARRAY_ZERO(arr_)	\
 	is_filled((const char *) (arr_), 0, sizeof(arr_) + MUST_BE_ARRAY(arr_))
 
-# ifndef BIT
-#  define BIT(x_) (1U << (x_))
+# ifndef BIT32
+#  define BIT32(x_) (1U << (x_))
 # endif
 
-# define FLAG(name_) name_ = BIT(name_##_BIT)
+# ifndef BIT64
+#  define BIT64(x_) (1ULL << (x_))
+# endif
+
+# ifndef MASK32
+#  define MASK32(x_) (BIT32(x_) - 1U)
+# endif
+
+# ifndef MASK64
+#  define MASK64(x_) (BIT64(x_) - 1ULL)
+# endif
+
+/*
+ * "Safe" versions that avoid UB for values that are >= type bit size
+ * (the usually expected behaviour of the bit shift in that case is zero,
+ * but at least powerpc is notorious for returning the input value when shift
+ * by 64 bits is performed).
+ */
+
+# define BIT32_SAFE(x_) ((x_) < 32 ? BIT32(x_) : 0)
+# define BIT64_SAFE(x_) ((x_) < 64 ? BIT64(x_) : 0)
+# define MASK32_SAFE(x_) (BIT32_SAFE(x_) - 1U)
+# define MASK64_SAFE(x_) (BIT64_SAFE(x_) - 1ULL)
+
+# define FLAG(name_) name_ = BIT32(name_##_BIT)
 
 #endif /* !STRACE_MACROS_H */
-- 
2.1.4