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* [glibc] stdlib: Fix stdbit.h with -Wconversion for clang
@ 2024-01-05 17:53 Adhemerval Zanella
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From: Adhemerval Zanella @ 2024-01-05 17:53 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=48ef5aeb1b75991e1f92c9756e73ddbbe96b1bee
commit 48ef5aeb1b75991e1f92c9756e73ddbbe96b1bee
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Thu Jan 4 14:59:28 2024 -0300
stdlib: Fix stdbit.h with -Wconversion for clang
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.
Diff:
---
stdlib/stdbit.h | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/stdlib/stdbit.h b/stdlib/stdbit.h
index 61165dd725..f334eb174d 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)
@@ -170,8 +171,8 @@ extern unsigned int stdc_trailing_zeros_ull (unsigned long long int __x)
#define stdc_trailing_zeros(x) \
(sizeof (x) == 8 ? stdc_trailing_zeros_ull (x) \
: sizeof (x) == 4 ? stdc_trailing_zeros_ui (x) \
- : sizeof (x) == 2 ? stdc_trailing_zeros_us (x) \
- : stdc_trailing_zeros_uc (x))
+ : sizeof (x) == 2 ? stdc_trailing_zeros_us (__pacify_uint16 (x)) \
+ : stdc_trailing_zeros_uc (__pacify_uint8 (x)))
#if __GNUC_PREREQ (3, 4) || __glibc_has_builtin (__builtin_ctzll)
static __always_inline unsigned int
@@ -274,8 +275,8 @@ extern unsigned int stdc_first_leading_zero_ull (unsigned long long int __x)
#define stdc_first_leading_zero(x) \
(sizeof (x) == 8 ? stdc_first_leading_zero_ull (x) \
: sizeof (x) == 4 ? stdc_first_leading_zero_ui (x) \
- : sizeof (x) == 2 ? stdc_first_leading_zero_us (x) \
- : stdc_first_leading_zero_uc (x))
+ : sizeof (x) == 2 ? stdc_first_leading_zero_us (__pacify_uint16 (x)) \
+ : stdc_first_leading_zero_uc (__pacify_uint8 (x)))
#if __GNUC_PREREQ (3, 4) || __glibc_has_builtin (__builtin_clzll)
static __always_inline unsigned int
@@ -328,8 +329,8 @@ extern unsigned int stdc_first_leading_one_ull (unsigned long long int __x)
#define stdc_first_leading_one(x) \
(sizeof (x) == 8 ? stdc_first_leading_one_ull (x) \
: sizeof (x) == 4 ? stdc_first_leading_one_ui (x) \
- : sizeof (x) == 2 ? stdc_first_leading_one_us (x) \
- : stdc_first_leading_one_uc (x))
+ : sizeof (x) == 2 ? stdc_first_leading_one_us (__pacify_uint16 (x)) \
+ : stdc_first_leading_one_uc (__pacify_uint8 (x)))
#if __GNUC_PREREQ (3, 4) || __glibc_has_builtin (__builtin_clzll)
static __always_inline unsigned int
@@ -382,8 +383,8 @@ extern unsigned int stdc_first_trailing_zero_ull (unsigned long long int __x)
#define stdc_first_trailing_zero(x) \
(sizeof (x) == 8 ? stdc_first_trailing_zero_ull (x) \
: sizeof (x) == 4 ? stdc_first_trailing_zero_ui (x) \
- : sizeof (x) == 2 ? stdc_first_trailing_zero_us (x) \
- : stdc_first_trailing_zero_uc (x))
+ : sizeof (x) == 2 ? stdc_first_trailing_zero_us (__pacify_uint16 (x)) \
+ : stdc_first_trailing_zero_uc (__pacify_uint8 (x)))
#if __GNUC_PREREQ (3, 4) || __glibc_has_builtin (__builtin_ctzll)
static __always_inline unsigned int
@@ -436,8 +437,8 @@ extern unsigned int stdc_first_trailing_one_ull (unsigned long long int __x)
#define stdc_first_trailing_one(x) \
(sizeof (x) == 8 ? stdc_first_trailing_one_ull (x) \
: sizeof (x) == 4 ? stdc_first_trailing_one_ui (x) \
- : sizeof (x) == 2 ? stdc_first_trailing_one_us (x) \
- : stdc_first_trailing_one_uc (x))
+ : sizeof (x) == 2 ? stdc_first_trailing_one_us (__pacify_uint16 (x)) \
+ : stdc_first_trailing_one_uc (__pacify_uint8 (x)))
#if __GNUC_PREREQ (3, 4) || __glibc_has_builtin (__builtin_ctzll)
static __always_inline unsigned int
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2024-01-05 17:53 [glibc] stdlib: Fix stdbit.h with -Wconversion for clang Adhemerval Zanella
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