[PATCH 09/11] alloc_buffer: Apply asm redirection before first use

[Fangrui Song]

On 2022-10-28, Adhemerval Zanella via Libc-alpha wrote:
>Compilers may not be able to apply asm redirections to functions after
>these functions are used for the first time, e.g. clang 13.

You may say "clang 15".  (clang 15.0.x has been released and clang still doesn't support this.
I think this is very difficult to support....  https://maskray.me/blog/2021-10-10-when-can-glibc-be-built-with-clang#asm-label-after-first-use
"Clang's one-function-at-a-time parsing and code generation strategy.")


Thanks.  This fixed

In file included from mntent.c:21:
../include/allocate_once.h:92:20: error: cannot apply asm label to function after its first use
libc_hidden_proto (__libc_allocate_once_slow)
~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
./../include/libc-symbols.h:613:58: note: expanded from macro 'libc_hidden_proto'
# define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
                                            ~~~~~~~~~~~~~~^~~~~~~~~~~~~~
./../include/libc-symbols.h:513:19: note: expanded from macro 'hidden_proto'
   __hidden_proto (name, , __GI_##name, ##attrs)
   ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./../include/libc-symbols.h:519:33: note: expanded from macro '__hidden_proto'
   extern thread __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
                                 ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.


Reviewed-by: Fangrui Song <maskray@google.com>