[SCM] GNU Autoconf source repository branch, master, updated. v2.63-235-gfd651ae

[Eric Blake]

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- Log -----------------------------------------------------------------
commit fd651ae835b1b7a354bf4cd3d4b2fc0bab17656a
Author: Eric Blake <address@hidden>
Date:   Tue Dec 2 11:51:44 2008 -0700

    Improve AC_STATE_SAVE.
    
    * tests/local.at (AC_STATE_SAVE): Avoid ls -1, and use one less
    process by hoisting the uniqueness check into sed.
    * doc/autoconf.texi (Limitations of Usual Tools) <ls>: Mention
    MacOS bug.
    
    Signed-off-by: Eric Blake <address@hidden>

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

Summary of changes:
 ChangeLog         |    8 ++++++++
 doc/autoconf.texi |   10 ++++++++++
 tests/local.at    |   20 +++++++++++++++++---
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 7ca53e9..cd343d8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2008-12-03  Eric Blake  <address@hidden>
+
+       Improve AC_STATE_SAVE.
+       * tests/local.at (AC_STATE_SAVE): Avoid ls -1, and use one less
+       process by hoisting the uniqueness check into sed.
+       * doc/autoconf.texi (Limitations of Usual Tools) <ls>: Mention
+       MacOS bug.
+
 2008-12-02  Eric Blake  <address@hidden>
 
        Avoid MacOS readdir bug in testsuite.
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 1decd4b..fe28f39 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -16575,6 +16575,16 @@ was equivalent to @samp{sources='*.c not found'} in 
the absence of
 @samp{.c} files.  This is no longer a practical problem, since current
 @command{ls} implementations send diagnostics to standard error.
 
+The behavior of @command{ls} on a directory that is being concurrently
+modified is not always predictable, because of a data race where cached
+information returned by @code{readdir} does not match the current
+directory state.  In fact, MacOS 10.5 has an intermittent bug where
address@hidden, and thus @command{ls}, sometimes lists a file more than
+once if other files were added or removed from the directory immediately
+prior to the @command{ls} call.  Since @command{ls} already sorts its
+output, the duplicate entries can be avoided by piping the results
+through @code{uniq}.
+
 @anchor{mkdir}
 @item @command{mkdir}
 @c ------------------
diff --git a/tests/local.at b/tests/local.at
index 2ec7bc5..ba81e7c 100644
--- a/tests/local.at
+++ b/tests/local.at
@@ -197,11 +197,25 @@ m4_define([AT_CONFIGURE_AC],
 # confirm that no test modifies variables outside the Autoconf namespace or
 # leaves temporary files.  AT_CONFIG_CMP uses the variable dumps to confirm 
that
 # tests have the same side effects regardless of caching.
-# The sort -u is necessary, since MacOS 10.5 has a bug where readdir can
-# list a file multiple times in a rapidly changing directory.
+#
+# The sed script duplicates uniq functionality (thanks to 'info sed
+# uniq' for the recipe), in order to avoid a MacOS 10.5 bug where
+# readdir can list a file multiple times in a rapidly changing
+# directory, while avoiding yet another fork.
 m4_defun([AC_STATE_SAVE],
 [(set) 2>&1 | sort >state-env.$][1
-ls -1 | sed '/^at-/d;/^state-/d;/^config\./d' | sort -u >state-ls.$][1
+ls | sed '/^at-/d;/^state-/d;/^config\./d
+  h
+  :b
+  $b
+  N
+  /^\(.*\)\n\1$/ {
+    g
+    bb
+  }
+  $b
+  P
+  D' >state-ls.$][1
 ])# AC_STATE_SAVE
 ]])
 


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