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From 3f3dd44f1964c54b55e8c84343579bd7c1924df5 Mon Sep 17 00:00:00 2001
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From: Eugene Syromyatnikov <evgsyr@gmail.com>
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Date: Wed, 18 Aug 2021 21:49:12 +0200
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Subject: [PATCH 148/150] macros: expand BIT macros, add MASK macros; add
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*_SAFE macros
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These macros might make reading a code that often converts between powers
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of 2 and values/masks a bit easier; moreover, the *_SAFE versions should
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help in cases where the shift values are expected to be equal to the type
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bit width (which lead to UB otherwise).
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Switching from BIT to BIT32 should also clarify bitness, which may be somewhat
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murky at times (cf. printxval, printflags, and printxvals).
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* src/macros.h [!BIT] (BIT): Rename to...
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[!BIT32] (BIT32): ...this.
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[!BIT64] (BIT64): New macro.
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[!MASK32] (MASK32): Likewise.
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[!MASK64] (MASK64): Likewise.
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(BIT32_SAFE, BIT64_SAFE, MASK32_SAFE, MASK64_SAFE): New macros.
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(FLAG): Use BIT32.
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---
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src/macros.h | 30 +++++++++++++++++++++++++++---
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1 file changed, 27 insertions(+), 3 deletions(-)
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diff --git a/src/macros.h b/src/macros.h
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index 467f5d0..2d7a83d 100644
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--- a/src/macros.h
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+++ b/src/macros.h
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@@ -78,10 +78,34 @@ is_filled(const char *ptr, char fill, size_t size)
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# define IS_ARRAY_ZERO(arr_) \
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is_filled((const char *) (arr_), 0, sizeof(arr_) + MUST_BE_ARRAY(arr_))
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-# ifndef BIT
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-# define BIT(x_) (1U << (x_))
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+# ifndef BIT32
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+# define BIT32(x_) (1U << (x_))
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# endif
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-# define FLAG(name_) name_ = BIT(name_##_BIT)
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+# ifndef BIT64
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+# define BIT64(x_) (1ULL << (x_))
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+# endif
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+
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+# ifndef MASK32
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+# define MASK32(x_) (BIT32(x_) - 1U)
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+# endif
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+
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+# ifndef MASK64
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+# define MASK64(x_) (BIT64(x_) - 1ULL)
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+# endif
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+
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+/*
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+ * "Safe" versions that avoid UB for values that are >= type bit size
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+ * (the usually expected behaviour of the bit shift in that case is zero,
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+ * but at least powerpc is notorious for returning the input value when shift
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+ * by 64 bits is performed).
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+ */
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+
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+# define BIT32_SAFE(x_) ((x_) < 32 ? BIT32(x_) : 0)
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+# define BIT64_SAFE(x_) ((x_) < 64 ? BIT64(x_) : 0)
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+# define MASK32_SAFE(x_) (BIT32_SAFE(x_) - 1U)
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+# define MASK64_SAFE(x_) (BIT64_SAFE(x_) - 1ULL)
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+
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+# define FLAG(name_) name_ = BIT32(name_##_BIT)
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#endif /* !STRACE_MACROS_H */
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--
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2.1.4
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