sort: fix silent exit upon SIGPIPE from --compress-program

* src/sort.c (main): Ignore SIGPIPE so we've more control over
how we handle for stdout and compression programs.
(sort_die): Handle EPIPE from stdout and mimic a standard SIGPIPE,
otherwise reverting to a standard exit(SORT_FAILURE);
* tests/sort/sort-compress-proc.sh: Add a test case.
* NEWS: Mention the bug fix.

1 files changed, 22 insertions, 4 deletions

diff --git a/tests/sort/sort-compress-proc.sh b/tests/sort/sort-compress-proc.sh
index c410b7fce..203342924 100755
--- a/tests/sort/sort-compress-proc.sh
+++ b/tests/sort/sort-compress-proc.sh
@@ -17,7 +17,7 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 . "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
-print_ver_ sort
+print_ver_ sort kill
 expensive_
 
 # Terminate any background processes
@@ -25,9 +25,9 @@ cleanup_() { kill $pid 2>/dev/null && wait $pid; }
 
 SORT_FAILURE=2
 
-seq -w 2000 > exp || fail=1
-tac exp > in || fail=1
-insize=$(stat -c %s - <in) || fail=1
+seq -w 2000 > exp || framework_failure_
+tac exp > in || framework_failure_
+insize=$(stat -c %s - <in) || framework_failure_
 
 # This compressor's behavior is adjustable via environment variables.
 export PRE_COMPRESS=
@@ -42,6 +42,24 @@ EOF
 
 chmod +x compress
 
+# "Early exit" test
+#
+# In this test, the compressor exits before reading all (any) data.
+# Until coreutils 9.9 'sort' could get a SIGPIPE writing to the
+# exited processes and silently exit.  Note the same issue can happen
+# irrespective of exit status.  It's more likely to happen in the
+# case of the child exiting with success, and if we write more data
+# (hence the --batch-size=30 and double "in").  Note we check sort doesn't
+# get SIGPIPE rather than if it returns SORT_FAILURE, because there is
+# the theoretical possibility that the kernel could buffer the
+# amount of data we're writing here and not issue the EPIPE to sort.
+# In other words we currently may not detect failures in the extreme edge case
+# of writing a small amount of data to a compressor that exits 0
+# while not reading all the data presented.
+PRE_COMPRESS='exit 0' \
+ sort --compress-program=./compress -S 1k --batch-size=30 ./in ./in > out
+test $(env kill -l $?) = 'PIPE' && fail=1
+
 # "Impatient exit" tests
 #
 # In these test cases, the biggest compressor (or decompressor) exits