From fed1a562c3d1f3cf3cac0dd1413679191ac43002 Mon Sep 17 00:00:00 2001
From: Martijn Dekker <martijn@inlv.org>
Date: Fri, 17 Jan 2020 13:02:57 +0100
Subject: [PATCH] Make I/O errors fatal instead of mere warnings (#63)

An input/output error indicates a fatal condition, even if it
occurs when closing a file. Awk should not return success on I/O
error, but treat I/O errors as it already treats write errors.

Test case:

$ (trap '' PIPE; awk 'BEGIN { print "hi"; }'; echo "E $?" >&2) | :
awk: i/o error occurred while closing /dev/stdout
 source line number 1
E 2

The test case pipes a line into a dummy command that reads no
input, with SIGPIPE ignored so we rely on awk's own I/O checking.
No write error is detected, because the pipe is buffered; the
broken pipe is only detected as an I/O error on closing stdout.

Before this commit, "E 0" was printed (indicating status 0/success)
because an I/O error merely produced a warning. A shell script
was unable to detect the I/O error using the exit status.
---
 FIXES          | 4 ++++
 run.c          | 8 ++++----
 testdir/T.misc | 5 +++++
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/FIXES b/FIXES
index 6889e30..aac4a4a 100644
--- a/FIXES
+++ b/FIXES
@@ -25,6 +25,10 @@ THIS SOFTWARE.
 This file lists all bug fixes, changes, etc., made since the AWK book
 was sent to the printers in August, 1987.
 
+January 9, 2020:
+	Input/output errors on closing files are now fatal instead of
+	mere warnings. Thanks to Martijn Dekker <martijn@inlv.org>.
+
 January 5, 2020:
 	Fix a bug in the concatentation of two string constants into
 	one done in the grammar.  Fixes GitHub issue #61.  Thanks
diff --git a/run.c b/run.c
index a331449..136e20a 100644
--- a/run.c
+++ b/run.c
@@ -1769,13 +1769,13 @@ Cell *closefile(Node **a, int n)
 	for (i = 0; i < nfiles; i++) {
 		if (files[i].fname && strcmp(x->sval, files[i].fname) == 0) {
 			if (ferror(files[i].fp))
-				WARNING( "i/o error occurred on %s", files[i].fname );
+				FATAL( "i/o error occurred on %s", files[i].fname );
 			if (files[i].mode == '|' || files[i].mode == LE)
 				stat = pclose(files[i].fp);
 			else
 				stat = fclose(files[i].fp);
 			if (stat == EOF)
-				WARNING( "i/o error occurred closing %s", files[i].fname );
+				FATAL( "i/o error occurred closing %s", files[i].fname );
 			if (i > 2)	/* don't do /dev/std... */
 				xfree(files[i].fname);
 			files[i].fname = NULL;	/* watch out for ref thru this */
@@ -1795,13 +1795,13 @@ void closeall(void)
 	for (i = 0; i < FOPEN_MAX; i++) {
 		if (files[i].fp) {
 			if (ferror(files[i].fp))
-				WARNING( "i/o error occurred on %s", files[i].fname );
+				FATAL( "i/o error occurred on %s", files[i].fname );
 			if (files[i].mode == '|' || files[i].mode == LE)
 				stat = pclose(files[i].fp);
 			else
 				stat = fclose(files[i].fp);
 			if (stat == EOF)
-				WARNING( "i/o error occurred while closing %s", files[i].fname );
+				FATAL( "i/o error occurred while closing %s", files[i].fname );
 		}
 	}
 }
diff --git a/testdir/T.misc b/testdir/T.misc
index 7fc196a..a191ae2 100755
--- a/testdir/T.misc
+++ b/testdir/T.misc
@@ -466,3 +466,8 @@ echo '' >foo0
 $awk 'END { print NF, $0 }' foo0 >foo1
 awk '{ print NF, $0 }' foo0| tail -1 >foo2
 cmp -s foo1 foo2 || echo 'BAD: T.misc END must preserve $0'
+
+# Check for nonzero exit status on I/O error.
+echo 'E 2' >foo1
+(trap '' PIPE; "$awk" 'BEGIN { print "hi"; }' 2>/dev/null; echo "E $?" >foo2) | :
+cmp -s foo1 foo2 || echo 'BAD: T.misc exit status on I/O error'