GNU C Library master sources branch master updated. glibc-2.25-202-ga42478b

[fw at sourceware dot org]

This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GNU C Library master sources".

The branch, master has been updated
       via  a42478b7bf10e9f890466c91280d9b24908ca980 (commit)
      from  38efe8c5a5c1676f54481caa81980a93f7223479 (commit)

Those revisions listed above that are new to this repository have
not appeared on any other notification email; so we list those
revisions in full, below.

- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=a42478b7bf10e9f890466c91280d9b24908ca980

commit a42478b7bf10e9f890466c91280d9b24908ca980
Author: Florian Weimer <fweimer@redhat.com>
Date:   Tue Apr 11 18:04:34 2017 +0200

    manual: readdir, readdir64 are thread-safe
    
    They only modify the state in the dirstream argument, and we
    generally do not treat this as a reason to mark a function as
    not thread-safe.  For an example, see random_r, which is marked
    as thread-safe even though the random state is not protected
    by a lock.

diff --git a/ChangeLog b/ChangeLog
index ec7617d..0dd3057 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-04-11  Florian Weimer  <fweimer@redhat.com>
+	    Zack Weinberg  <zackw@panix.com>
+
+	* manual/filesys.texi (Reading/Closing Directory): Mark readdir,
+	readdir64 as thread-safe.  Update warning about readdir_r.
+
 2017-04-10  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
 	* sysdeps/unix/sysv/linux/x86/Implies: New file.
diff --git a/manual/filesys.texi b/manual/filesys.texi
index edc7c64..a255c8f 100644
--- a/manual/filesys.texi
+++ b/manual/filesys.texi
@@ -478,7 +478,7 @@ symbols are declared in the header file @file{dirent.h}.
 @comment dirent.h
 @comment POSIX.1
 @deftypefun {struct dirent *} readdir (DIR *@var{dirstream})
-@safety{@prelim{}@mtunsafe{@mtasurace{:dirstream}}@asunsafe{@asulock{}}@acunsafe{@aculock{}}}
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{}}}
 @c This function holds dirstream's non-recursive lock, which brings
 @c about the usual issues with locks and async signals and cancellation,
 @c but the lock taking is not enough to make the returned value safe to
@@ -507,13 +507,24 @@ must set @code{errno} to zero before calling @code{readdir}.  To avoid
 entering an infinite loop, you should stop reading from the directory
 after the first error.
 
-In POSIX.1-2008, @code{readdir} is not thread-safe.  In @theglibc{}
-implementation, it is safe to call @code{readdir} concurrently on
-different @var{dirstream}s, but multiple threads accessing the same
-@var{dirstream} result in undefined behavior.  @code{readdir_r} is a
-fully thread-safe alternative, but suffers from poor portability (see
-below).  It is recommended that you use @code{readdir}, with external
-locking if multiple threads access the same @var{dirstream}.
+@strong{Caution:} The pointer returned by @code{readdir} points to
+a buffer within the @code{DIR} object.  The data in that buffer will
+be overwritten by the next call to @code{readdir}.  You must take care,
+for instance, to copy the @code{d_name} string if you need it later.
+
+Because of this, it is not safe to share a @code{DIR} object among
+multiple threads, unless you use your own locking to ensure that
+no thread calls @code{readdir} while another thread is still using the
+data from the previous call.  In @theglibc{}, it is safe to call
+@code{readdir} from multiple threads as long as each thread uses
+its own @code{DIR} object.  POSIX.1-2008 does not require this to
+be safe, but we are not aware of any operating systems where it
+does not work.
+
+@code{readdir_r} allows you to provide your own buffer for the
+@code{struct dirent}, but it is less portable than @code{readdir}, and
+has problems with very long filenames (see below).  We recommend
+you use @code{readdir}, but do not share @code{DIR} objects.
 @end deftypefun
 
 @comment dirent.h
@@ -592,7 +603,7 @@ of the last two functions.
 @comment dirent.h
 @comment LFS
 @deftypefun {struct dirent64 *} readdir64 (DIR *@var{dirstream})
-@safety{@prelim{}@mtunsafe{@mtasurace{:dirstream}}@asunsafe{@asulock{}}@acunsafe{@aculock{}}}
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{}}}
 The @code{readdir64} function is just like the @code{readdir} function
 except that it returns a pointer to a record of type @code{struct
 dirent64}.  Some of the members of this data type (notably @code{d_ino})

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog           |    6 ++++++
 manual/filesys.texi |   29 ++++++++++++++++++++---------
 2 files changed, 26 insertions(+), 9 deletions(-)


hooks/post-receive
-- 
GNU C Library master sources