Re: [PATCH v2 1/4] libio: Assume _IO_MTSAFE_IO

[Florian Weimer <fweimer@redhat.com>]

* Adhemerval Zanella via Libc-alpha:

> It is already set by default on all supported architectures and it is
> an expectation that stdio works on multi-threaded environments.

So … this cleanup has got stuck in the past because it's actually more
than just a cleanup.  We actually build most of glibc without libio
locking.  Looks like misc/ nss/ posix/ have not been covered before.

Maybe we should just file a bug for the missing locking and fix this
with this commit?

> index 5af476c48b..c186375c31 100644
> --- a/sysdeps/nptl/libc-lock.h
> +++ b/sysdeps/nptl/libc-lock.h
> @@ -25,7 +25,7 @@
>  
>  
>  /* Mutex type.  */
> -#if defined _LIBC || defined _IO_MTSAFE_IO
> +#if defined _LIBC
>  # if (!IS_IN (libc) && !IS_IN (libpthread)) || !defined _LIBC
>  typedef struct { pthread_mutex_t mutex; } __libc_lock_recursive_t;
>  # else

This doesn't look quite right.  Would we want to compile this
unconditionally now?

There's also some weirdness I can't explain.  I get strange before/after
symbol differences:

DIFF eu-readelf -s after strip: nptl/pthread_rwlock_unlock.os
--- /tmp/Left-ltjeu50v.o        2022-04-27 14:29:39.070599437 +0200
+++ /tmp/Right-jee20kfm.o       2022-04-27 14:29:39.074599395 +0200
@@ -1,5 +1,5 @@
 
-Symbol table [11] '.symtab' contains 14 entries:
+Symbol table [11] '.symtab' contains 13 entries:
  4 local symbols  String table: [12] '.strtab'
   Num:            Value   Size Type    Bind   Vis          Ndx Name
     0: 0000000000000000      0 NOTYPE  LOCAL  DEFAULT    UNDEF 
@@ -12,7 +12,6 @@
     7: 0000000000000000    463 FUNC    GLOBAL DEFAULT        1 ___pthread_rwlock_unlo>
     8: 0000000000000000      0 NOTYPE  GLOBAL DEFAULT    UNDEF __GI___libc_fatal
     9: 0000000000000000    463 FUNC    GLOBAL DEFAULT        1 __GI___pthread_rwlock_>
-   10: 0000000000000000    463 FUNC    GLOBAL DEFAULT        1 __pthread_rwlock_unlock
-   11: 0000000000000000    463 FUNC    GLOBAL DEFAULT        1 __pthread_rwlock_unloc>
-   12: 0000000000000000    463 FUNC    GLOBAL DEFAULT        1 pthread_rwlock_unlock@>
-   13: 0000000000000000    463 FUNC    GLOBAL DEFAULT        1 pthread_rwlock_unlock@>
+   10: 0000000000000000    463 FUNC    GLOBAL DEFAULT        1 __pthread_rwlock_unloc>
+   11: 0000000000000000    463 FUNC    GLOBAL DEFAULT        1 pthread_rwlock_unlock@>
+   12: 0000000000000000    463 FUNC    GLOBAL DEFAULT        1 pthread_rwlock_unlock@>

Can you reproduce this?

Thanks,
Florian