From: Fangrui Song <maskray@google.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH 08/11] configure: Use -Wno-ignored-attributes if compiler warns about multiple aliases
Date: Fri, 28 Oct 2022 22:59:36 -0700 [thread overview]
Message-ID: <20221029055936.y4qtf52hxnqba2en@google.com> (raw)
In-Reply-To: <20221028173532.876027-9-adhemerval.zanella@linaro.org>
On 2022-10-28, Adhemerval Zanella via Libc-alpha wrote:
>clang emits an warning when a double alias redirection is used, to warn
>the the original symbol will be used even when weak definition is
>overridden. Howerver, this is a common pattern for weak_alias, where
>multiple alias are set to same symbol.
Confirmed that the pattern is common.
% rg -U 'libc_hidden_def.*\nweak_alias.*\nlibc_hidden_weak' -l
login/getlogin_r.c
libio/iofgets_u.c
libio/iofflush.c
libio/iofputs_u.c
libio/iofflush_u.c
libio/iofgets.c
libio/fileno.c
string/memmem.c
resource/getrlimit64.c
string/argz-next.c
inet/if_index.c
io/open.c
string/basename.c
wcsmbs/wmemset.c
wcsmbs/wcschr.c
wcsmbs/wmemchr.c
wctype/wcfuncs.c
resolv/inet_pton.c
sysdeps/x86_64/wmemchr.S
sysdeps/x86_64/memset.S
sysdeps/unix/getlogin_r.c
sysdeps/x86_64/wcschr.S
sysdeps/mach/hurd/getpid.c
sysdeps/mach/hurd/read.c
sysdeps/mach/hurd/write.c
sysdeps/mach/hurd/getlogin_r.c
sysdeps/mach/hurd/if_index.c
sysdeps/mach/hurd/fcntl.c
sysdeps/mach/hurd/open.c
sysdeps/unix/sysv/linux/getlogin_r.c
sysdeps/unix/sysv/linux/fcntl64.c
sysdeps/unix/sysv/linux/if_index.c
The three macros can be reordered and there may be more results.
I just took some notes here https://maskray.me/blog/2021-10-10-when-can-glibc-be-built-with-clang#alias-to-a-weak-alias
I feel that the pattern is ugly but I cannot figure out a better way. Clang has a reasonable diagnostic. It is fine to
ignore it as the Clang symbol codegen matches GCC.
```
26: 0000000000000000 596 FUNC GLOBAL HIDDEN 1 __GI___mbrtowc
33: 0000000000000000 596 FUNC GLOBAL DEFAULT 1 __mbrtowc
34: 0000000000000000 596 FUNC WEAK HIDDEN 1 __GI_mbrtowc
35: 0000000000000000 596 FUNC WEAK DEFAULT 1 mbrtowc
```
So here is a Reviewed-by tag: but I really hope that we can come up with a better way.
Reviewed-by: Fangrui Song <maskray@google.com>
next prev parent reply other threads:[~2022-10-29 5:59 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-28 17:35 [PATCH 00/11] Initial fixes for clang build support Adhemerval Zanella
2022-10-28 17:35 ` [PATCH 01/11] stdlib/longlong.h: Remove incorrect lvalue to rvalue conversion from asm output constraints Adhemerval Zanella
2022-10-28 21:05 ` Joseph Myers
2022-10-28 21:32 ` Fangrui Song
2022-10-31 18:32 ` Adhemerval Zanella Netto
2022-11-01 13:56 ` Adhemerval Zanella Netto
2022-11-01 14:18 ` Joseph Myers
2022-11-01 17:05 ` Adhemerval Zanella Netto
2022-11-02 15:14 ` Cristian Rodríguez
2022-11-02 17:10 ` Adhemerval Zanella Netto
2022-11-02 19:43 ` Cristian Rodríguez
2022-11-03 12:17 ` Adhemerval Zanella Netto
2022-11-01 17:11 ` Andrew Pinski
2022-11-06 19:30 ` Fangrui Song
2022-11-06 19:32 ` Fangrui Song
2022-11-07 13:39 ` Adhemerval Zanella Netto
2022-10-28 17:35 ` [PATCH 02/11] Disable __USE_EXTERN_INLINES for clang Adhemerval Zanella
2022-10-28 21:06 ` Joseph Myers
2022-10-28 22:02 ` Fangrui Song
2022-10-31 18:33 ` Adhemerval Zanella Netto
2022-10-28 17:35 ` [PATCH 03/11] Rewrite find_cxx_header config configure.ac Adhemerval Zanella
2022-10-29 4:03 ` Fangrui Song
2022-10-31 19:30 ` Adhemerval Zanella Netto
2022-10-28 17:35 ` [PATCH 04/11] linux: Move hidden_proto before static inline usage on not-cancel.h Adhemerval Zanella
2022-10-29 4:23 ` Fangrui Song
2022-10-31 19:48 ` Adhemerval Zanella Netto
2022-10-28 17:35 ` [PATCH 05/11] intl: Fix clang -Wunused-but-set-variable on plural.c Adhemerval Zanella
2022-10-29 0:44 ` Fangrui Song
2022-10-31 19:54 ` Adhemerval Zanella Netto
2022-10-28 17:35 ` [PATCH 06/11] Disable use of -fsignaling-nans if compiler does not support it Adhemerval Zanella
2022-10-29 4:19 ` Fangrui Song
2022-10-31 20:01 ` Fangrui Song
2022-10-28 17:35 ` [PATCH 07/11] stdlib: Move attribute_hidden definition to function prototype at gmp.h Adhemerval Zanella
2022-10-29 4:37 ` Fangrui Song
2022-10-31 19:55 ` Adhemerval Zanella Netto
2022-10-28 17:35 ` [PATCH 08/11] configure: Use -Wno-ignored-attributes if compiler warns about multiple aliases Adhemerval Zanella
2022-10-29 5:59 ` Fangrui Song [this message]
2022-10-31 19:59 ` Adhemerval Zanella Netto
2022-10-31 20:11 ` Fangrui Song
2022-10-28 17:35 ` [PATCH 09/11] alloc_buffer: Apply asm redirection before first use Adhemerval Zanella
2022-10-29 0:32 ` Fangrui Song
2022-10-31 20:01 ` Adhemerval Zanella Netto
2022-10-28 17:35 ` [PATCH 10/11] allocate_once: " Adhemerval Zanella
2022-10-29 0:34 ` Fangrui Song
2022-10-28 17:35 ` [PATCH 11/11] nptl: Fix pthread_create.c build with clang Adhemerval Zanella
2022-10-29 4:51 ` Fangrui Song
2022-10-31 20:03 ` Adhemerval Zanella Netto
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