grep: fix --devices=ACTION (-D) so stdin is once again exempt

An oversight in the 2.11 changes made it so "echo x|grep x" would
fail for those who set GREP_OPTIONS=--devices=skip.

* src/main.c (grepdesc): Ignore skip-related options when reading
from standard input.
* tests/skip-device: New file.  Test for the above.
* tests/Makefile.am (TESTS): Add it.
* doc/grep.texi (File and Directory Selection): Clarify this point,
documenting the stdin exemption.
* NEWS (Bug fixes): Mention it, and add a few "[fixed in ...] notes.
Reported by Tino Keitel in http://bugs.debian.org/669084,
and forwarded to bug-grep by Aníbal Monsalve Salazar.

5 files changed, 27 insertions, 5 deletions

diff --git a/NEWS b/NEWS
index b219b65e..a065394b 100644
--- a/NEWS
+++ b/NEWS
@@ -4,13 +4,17 @@ GNU grep NEWS                                    -*- outline -*-
 
 ** Bug fixes
 
+  "echo P|grep --devices=skip P" once again prints P, as it did in 2.10
+  [bug introduced in grep-2.11]
+
   grep no longer segfaults with -r --exclude-dir and no file operand.
   I.e., ":|grep -r --exclude-dir=D PAT" would segfault.
+  [bug introduced in grep-2.11]
 
   Recursive grep now uses fts for directory traversal, so it can
   handle much-larger directories without reporting things like "File
   name too long", and it can run much faster when dealing with large
-  directory hierarchies.
+  directory hierarchies. [bug present since the beginning]
 
   grep -E 'a{1000000000}' now reports an overflow error rather than
   silently acting like grep -E 'a\{1000000000}'.
@@ -27,6 +31,7 @@ GNU grep NEWS                                    -*- outline -*-
   use -R if you prefer the old behavior of following all symlinks and
   defaulting to reading all devices.
 
+
 * Noteworthy changes in release 2.11 (2012-03-02) [stable]
 
 ** Bug fixes
diff --git a/doc/grep.texi b/doc/grep.texi
index 1840e219..000a8446 100644
--- a/doc/grep.texi
+++ b/doc/grep.texi
@@ -614,6 +614,7 @@ By default, devices are read if they are on the command line or if the
 @option{-R} (@option{--dereference-recursive}) option is used, and are
 skipped if they are encountered recursively and the @option{-r}
 (@option{--recursive}) option is used.
+This option has no effect on a file that is read via standard input.
 
 @item -d @var{action}
 @itemx --directories=@var{action}
diff --git a/src/main.c b/src/main.c
index 82cae33c..c5a84898 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1367,10 +1367,11 @@ grepdesc (int desc, int command_line)
         suppressible_error (filename, errno);
       return status;
     }
-  if ((directories == SKIP_DIRECTORIES && S_ISDIR (st.st_mode))
-      || ((devices == SKIP_DEVICES
-           || (devices == READ_COMMAND_LINE_DEVICES && !command_line))
-          && is_device_mode (st.st_mode)))
+  if (desc != STDIN_FILENO
+      && ((directories == SKIP_DIRECTORIES && S_ISDIR (st.st_mode))
+          || ((devices == SKIP_DEVICES
+               || (devices == READ_COMMAND_LINE_DEVICES && !command_line))
+              && is_device_mode (st.st_mode))))
     goto closeout;
 
   /* If there is a regular file on stdout and the current file refers
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 13061fed..d0d622bd 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -78,6 +78,7 @@ TESTS =						\
   r-dot						\
   repetition-overflow				\
   reversed-range-endpoints			\
+  skip-device					\
   sjis-mb					\
   spencer1					\
   spencer1-locale				\
diff --git a/tests/skip-device b/tests/skip-device
new file mode 100755
index 00000000..40645ea1
--- /dev/null
+++ b/tests/skip-device
@@ -0,0 +1,14 @@
+#!/bin/sh
+# grep must ignore --devices=ACTION (-D) when reading stdin
+# For grep-2.11, this test would fail.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+
+# Test both with no file argument, and with "-".
+echo foo | grep -D skip foo - || fail=1
+echo foo | grep --devices=skip foo || fail=1
+
+# It's more insidious when the skip option is via the envvar:
+echo foo | GREP_OPTIONS=--devices=skip grep foo || fail=1
+
+Exit $fail