[PATCH 2/2] stdlib: Fix stdbit.h with -Wconversion for clang
Adhemerval Zanella
adhemerval.zanella@linaro.org
Thu Jan 4 19:47:31 GMT 2024
With clang 14 and also with main the tst-stdbit-Wconversion
issues the warnings:
../stdlib/stdbit.h:701:40: error: implicit conversion loses integer
precision: 'int' to 'uint16_t' (aka 'unsigned short')
[-Werror,-Wimplicit-int-conversion]
return __x == 0 ? 0 : ((uint16_t) 1) << (__bw16_inline (__x) - 1);
~~~~~~ ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
../stdlib/stdbit.h:707:39: error: implicit conversion loses integer
precision: 'int' to 'uint8_t' (aka 'unsigned char')
[-Werror,-Wimplicit-int-conversion]
return __x == 0 ? 0 : ((uint8_t) 1) << (__bw8_inline (__x) - 1);
~~~~~~ ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
../stdlib/stdbit.h:751:40: error: implicit conversion loses integer
precision: 'int' to 'uint16_t' (aka 'unsigned short')
[-Werror,-Wimplicit-int-conversion]
return __x <= 1 ? 1 : ((uint16_t) 2) << (__bw16_inline (__x - 1) - 1);
~~~~~~ ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../stdlib/stdbit.h:757:39: error: implicit conversion loses integer
precision: 'int' to 'uint8_t' (aka 'unsigned char')
[-Werror,-Wimplicit-int-conversion]
return __x <= 1 ? 1 : ((uint8_t) 2) << (__bw8_inline (__x - 1) - 1);
~~~~~~ ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tst-stdbit-Wconversion.c:45:31: error: implicit conversion loses integer
precision: 'unsigned short' to 'uint8_t' (aka 'unsigned char')
[-Werror,-Wimplicit-int-conversion]
(void) stdc_trailing_zeros (us);
~~~~~~~~~~~~~~~~~~~~~^~~
../stdlib/stdbit.h:164:30: note: expanded from macro
'stdc_trailing_zeros'
: stdc_trailing_zeros_uc (x))
~~~~~~~~~~~~~~~~~~~~~~~~^~
../stdlib/stdbit.h:191:52: note: expanded from macro
'stdc_trailing_zeros_uc'
# define stdc_trailing_zeros_uc(x) (__ctz8_inline (x))
~~~~~~~~~~~~~ ^
tst-stdbit-Wconversion.c:46:31: error: implicit conversion loses integer
precision: 'unsigned int' to 'uint16_t' (aka 'unsigned short')
[-Werror,-Wimplicit-int-conversion]
(void) stdc_trailing_zeros (ui);
~~~~~~~~~~~~~~~~~~~~~^~~
../stdlib/stdbit.h:163:48: note: expanded from macro
'stdc_trailing_zeros'
: sizeof (x) == 2 ? stdc_trailing_zeros_us (x) \
~~~~~~~~~~~~~~~~~~~~~~~~^~
../stdlib/stdbit.h:192:53: note: expanded from macro
'stdc_trailing_zeros_us'
# define stdc_trailing_zeros_us(x) (__ctz16_inline (x))
~~~~~~~~~~~~~~ ^
tst-stdbit-Wconversion.c:46:31: error: implicit conversion loses integer
precision: 'unsigned int' to 'uint8_t' (aka 'unsigned char')
[-Werror,-Wimplicit-int-conversion]
(void) stdc_trailing_zeros (ui);
~~~~~~~~~~~~~~~~~~~~~^~~
../stdlib/stdbit.h:164:30: note: expanded from macro
'stdc_trailing_zeros'
: stdc_trailing_zeros_uc (x))
~~~~~~~~~~~~~~~~~~~~~~~~^~
../stdlib/stdbit.h:191:52: note: expanded from macro
'stdc_trailing_zeros_uc'
# define stdc_trailing_zeros_uc(x) (__ctz8_inline (x))
~~~~~~~~~~~~~ ^
tst-stdbit-Wconversion.c:47:31: error: implicit conversion loses integer
precision: 'unsigned long' to 'uint16_t' (aka 'unsigned short')
[-Werror,-Wimplicit-int-conversion]
(void) stdc_trailing_zeros (ul);
~~~~~~~~~~~~~~~~~~~~~^~~
../stdlib/stdbit.h:163:48: note: expanded from macro
'stdc_trailing_zeros'
: sizeof (x) == 2 ? stdc_trailing_zeros_us (x) \
~~~~~~~~~~~~~~~~~~~~~~~~^~
../stdlib/stdbit.h:192:53: note: expanded from macro
'stdc_trailing_zeros_us'
# define stdc_trailing_zeros_us(x) (__ctz16_inline (x))
~~~~~~~~~~~~~~ ^
[...]
It seems to boiler down to __builtin_clz not having a variant for 8 or
16 bits. Fix it by explicit casting to the expected types. Although
not strickly required for older gcc, using the same __pacify macro
simpify the required code.
Checked on x86_64-linux-gnu and i686-linux-gnu.
---
stdlib/stdbit.h | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/stdlib/stdbit.h b/stdlib/stdbit.h
index 2945550385..9daf414651 100644
--- a/stdlib/stdbit.h
+++ b/stdlib/stdbit.h
@@ -42,7 +42,8 @@
__BEGIN_DECLS
/* Use __pacify_uint16 (N) instead of (uint16_t) (N) when the cast is helpful
- only to pacify older GCC (e.g., GCC 10 -Wconversion) or non-GCC. */
+ only to pacify older GCC (e.g., GCC 10 -Wconversion) or non-GCC (e.g
+ clang -Wimplicit-int-conversion). */
#if __GNUC_PREREQ (11, 0)
# define __pacify_uint8(n) (n)
# define __pacify_uint16(n) (n)
@@ -198,8 +199,8 @@ __ctz8_inline (uint8_t __x)
return __x == 0 ? 8U : (unsigned int) __builtin_ctz (__x);
}
-# define stdc_trailing_zeros_uc(x) (__ctz8_inline (x))
-# define stdc_trailing_zeros_us(x) (__ctz16_inline (x))
+# define stdc_trailing_zeros_uc(x) (__ctz8_inline (__pacify_uint8 (x)))
+# define stdc_trailing_zeros_us(x) (__ctz16_inline (__pacify_uint16 (x)))
# define stdc_trailing_zeros_ui(x) (__ctz32_inline (x))
# if __WORDSIZE == 64
# define stdc_trailing_zeros_ul(x) (__ctz64_inline (x))
@@ -302,8 +303,8 @@ __flz8_inline (uint8_t __x)
return __x == (uint8_t) -1 ? 0 : 1 + __clo8_inline (__x);
}
-# define stdc_first_leading_zero_uc(x) (__flz8_inline (x))
-# define stdc_first_leading_zero_us(x) (__flz16_inline (x))
+# define stdc_first_leading_zero_uc(x) (__flz8_inline (__pacify_uint8 (x)))
+# define stdc_first_leading_zero_us(x) (__flz16_inline (__pacify_uint16 (x)))
# define stdc_first_leading_zero_ui(x) (__flz32_inline (x))
# if __WORDSIZE == 64
# define stdc_first_leading_zero_ul(x) (__flz64_inline (x))
@@ -356,8 +357,8 @@ __flo8_inline (uint8_t __x)
return __x == 0 ? 0 : 1 + __clz8_inline (__x);
}
-# define stdc_first_leading_one_uc(x) (__flo8_inline (x))
-# define stdc_first_leading_one_us(x) (__flo16_inline (x))
+# define stdc_first_leading_one_uc(x) (__flo8_inline (__pacify_uint8 (x)))
+# define stdc_first_leading_one_us(x) (__flo16_inline (__pacify_uint16 (x)))
# define stdc_first_leading_one_ui(x) (__flo32_inline (x))
# if __WORDSIZE == 64
# define stdc_first_leading_one_ul(x) (__flo64_inline (x))
@@ -410,8 +411,8 @@ __ftz8_inline (uint8_t __x)
return __x == (uint8_t) -1 ? 0 : 1 + __cto8_inline (__x);
}
-# define stdc_first_trailing_zero_uc(x) (__ftz8_inline (x))
-# define stdc_first_trailing_zero_us(x) (__ftz16_inline (x))
+# define stdc_first_trailing_zero_uc(x) (__ftz8_inline (__pacify_uint8 (x)))
+# define stdc_first_trailing_zero_us(x) (__ftz16_inline (__pacify_uint16 (x)))
# define stdc_first_trailing_zero_ui(x) (__ftz32_inline (x))
# if __WORDSIZE == 64
# define stdc_first_trailing_zero_ul(x) (__ftz64_inline (x))
@@ -464,8 +465,8 @@ __fto8_inline (uint8_t __x)
return __x == 0 ? 0 : 1 + __ctz8_inline (__x);
}
-# define stdc_first_trailing_one_uc(x) (__fto8_inline (x))
-# define stdc_first_trailing_one_us(x) (__fto16_inline (x))
+# define stdc_first_trailing_one_uc(x) (__fto8_inline (__pacify_uint8 (x)))
+# define stdc_first_trailing_one_us(x) (__fto16_inline (__pacify_uint16 (x)))
# define stdc_first_trailing_one_ui(x) (__fto32_inline (x))
# if __WORDSIZE == 64
# define stdc_first_trailing_one_ul(x) (__fto64_inline (x))
--
2.34.1
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