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From: Adhemerval Zanella <azanella@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] stdlib: Fix stdbit.h with -Wconversion for clang Date: Fri, 5 Jan 2024 17:53:08 +0000 (GMT) [thread overview] Message-ID: <20240105175308.671793857400@sourceware.org> (raw) 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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