Improve handling of EPIPE and fflush.

5 files changed, 89 insertions, 38 deletions

diff --git a/ChangeLog b/ChangeLog
index a0f26b26..c430cd48 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,23 @@
+2017-03-20         Arnold D. Robbins     <arnold@skeeve.com>
+
+	Improve handling of EPIPE. Problems reported by
+	Alexandre Ferrieux <alexandre.ferrieux@orange.com>
+	and David Kerns <david.t.kerns@gmail.com>.
+
+	* awk.h (ignore_sigpipe, set_sigpipe_to_default,
+	non_fatal_flush_std): Declare new functions.
+	(ignore_sigpipe, set_sigpipe_to_default,
+	non_fatal_flush_std): New macros.
+	* builtin.c (do_fflush): When nonfatal not in force, flush
+	of stdout/stderr and EPIPE exits, simulating SIGPIPE, as
+	in nawk/mawk. Flush of other redirections with EPIPE now
+	also fatals.
+	(do_system): Use ignore_sipipe and set_sigpipe_to_default
+	instead of uglier inline ifdefed code.
+	* main.c (main): Ditto.
+	* io.c (redirect_string, two_way_open, gawk_popen): Ditto.
+	(flush_io): Use non_fatal_flush_std for stdout and stderr.
+
 2017-03-16         Arnold D. Robbins     <arnold@skeeve.com>
 
 	* configure.ac: Some cleanups.
diff --git a/awk.h b/awk.h
index aae5e7ec..163ad362 100644
--- a/awk.h
+++ b/awk.h
@@ -1584,6 +1584,10 @@ extern bool inrec(IOBUF *iop, int *errcode);
 extern int nextfile(IOBUF **curfile, bool skipping);
 extern bool is_non_fatal_std(FILE *fp);
 extern bool is_non_fatal_redirect(const char *str, size_t len);
+extern void ignore_sigpipe(void);
+extern void set_sigpipe_to_default(void);
+extern bool non_fatal_flush_std_file(FILE *fp);
+
 /* main.c */
 extern int arg_assign(char *arg, bool initing);
 extern int is_std_var(const char *var);
@@ -1958,3 +1962,11 @@ erealloc_real(void *ptr, size_t count, const char *where, const char *var, const
 
 	return ret;
 }
+
+#ifdef SIGPIPE
+#define ignore_sigpipe() signal(SIGPIPE, SIG_IGN)
+#define set_sigpipe_to_default() signal(SIGPIPE, SIG_DFL)
+#else
+#define ignore_sigpipe()
+#define set_sigpipe_to_default()
+#endif
diff --git a/builtin.c b/builtin.c
index 2acd9928..b92eb19d 100644
--- a/builtin.c
+++ b/builtin.c
@@ -133,7 +133,6 @@ wrerror:
 	if (fp == stdout && errno == EPIPE)
 		gawk_exit(EXIT_FATAL);
 
-
 	/* otherwise die verbosely */
 	if ((rp != NULL) ? is_non_fatal_redirect(rp->value, strlen(rp->value)) : is_non_fatal_std(fp))
 		update_ERRNO_int(errno);
@@ -245,13 +244,19 @@ do_fflush(int nargs)
 			return make_number((AWKNUM) status);
 		}
 		fp = rp->output.fp;
-		if (fp != NULL)
+		if (fp != NULL) {
 			status = rp->output.gawk_fflush(fp, rp->output.opaque);
-		else if ((rp->flag & RED_TWOWAY) != 0)
+
+			if (status != 0) {
+				if (! is_non_fatal_redirect(tmp->stptr, tmp->stlen))
+					fatal(_("fflush: cannot flush file `%.*s': %s"),
+						len, file, strerror(errno));
+			}
+		} else if ((rp->flag & RED_TWOWAY) != 0)
 				warning(_("fflush: cannot flush: two-way pipe `%.*s' has closed write end"),
 					len, file);
 	} else if ((fp = stdfile(tmp->stptr, tmp->stlen)) != NULL) {
-		status = fflush(fp);
+		status = (non_fatal_flush_std_file(fp) == false);
 	} else {
 		status = -1;
 		warning(_("fflush: `%.*s' is not an open file, pipe or co-process"), len, file);
@@ -2148,9 +2153,7 @@ do_system(int nargs)
 		cmd[tmp->stlen] = '\0';
 
 		os_restore_mode(fileno(stdin));
-#ifdef SIGPIPE
-		signal(SIGPIPE, SIG_DFL);
-#endif
+		set_sigpipe_to_default();
 
 		status = system(cmd);
 		/*
@@ -2176,9 +2179,7 @@ do_system(int nargs)
 
 		if ((BINMODE & BINMODE_INPUT) != 0)
 			os_setbinmode(fileno(stdin), O_BINARY);
-#ifdef SIGPIPE
-		signal(SIGPIPE, SIG_IGN);
-#endif
+		ignore_sigpipe();
 
 		cmd[tmp->stlen] = save;
 	}
diff --git a/io.c b/io.c
index cced126e..0da27575 100644
--- a/io.c
+++ b/io.c
@@ -899,9 +899,7 @@ redirect_string(const char *str, size_t explen, bool not_string,
 			(void) flush_io();
 
 			os_restore_mode(fileno(stdin));
-#ifdef SIGPIPE
-			signal(SIGPIPE, SIG_DFL);
-#endif
+			set_sigpipe_to_default();
 			/*
 			 * Don't check failure_fatal; see input pipe below.
 			 * Note that the failure happens upon failure to fork,
@@ -911,9 +909,7 @@ redirect_string(const char *str, size_t explen, bool not_string,
 			if ((rp->output.fp = popen(str, binmode("w"))) == NULL)
 				fatal(_("can't open pipe `%s' for output (%s)"),
 						str, strerror(errno));
-#ifdef SIGPIPE
-			signal(SIGPIPE, SIG_IGN);
-#endif
+			ignore_sigpipe();
 
 			/* set close-on-exec */
 			os_close_on_exec(fileno(rp->output.fp), str, "pipe", "to");
@@ -1392,6 +1388,36 @@ checkwarn:
 	return status;
 }
 
+/* non_fatal_flush_std_file --- flush a standard output file allowing for nonfatal setting */
+
+bool
+non_fatal_flush_std_file(FILE *fp)
+{
+	int status = fflush(fp);
+
+	if (status != 0) {
+		bool is_fatal = ! is_non_fatal_std(fp);
+
+		if (is_fatal) {
+			if (errno == EPIPE)
+				exit(EXIT_SUCCESS);	// simulate SIGPIPE
+			else
+				fatal(fp == stdout
+					? _("fflush: cannot flush standard output: %s")
+					: _("fflush: cannot flush standard error: %s"),
+						strerror(errno));
+		} else {
+			warning(fp == stdout
+				? _("error writing standard output (%s)")
+				: _("error writing standard error (%s)"),
+					strerror(errno));
+		}
+		return false;
+	}
+
+	return true;
+}
+
 /* flush_io --- flush all open output files */
 
 int
@@ -1401,21 +1427,18 @@ flush_io()
 	int status = 0;
 
 	errno = 0;
-	/* we don't warn about stdout/stderr if EPIPE, but we do error exit */
-	if (fflush(stdout)) {
-		if (errno != EPIPE)
-			warning(_("error writing standard output (%s)"), strerror(errno));
+	if (! non_fatal_flush_std_file(stdout))
 		status++;
-	}
-	if (fflush(stderr)) {
-		if (errno != EPIPE)
-			warning(_("error writing standard error (%s)"), strerror(errno));
+
+	errno = 0;
+	if (! non_fatal_flush_std_file(stderr))
 		status++;
-	}
+
+	// now for all open redirections
 	for (rp = red_head; rp != NULL; rp = rp->next) {
 		/* flush both files and pipes, what the heck */
 		if ((rp->flag & RED_WRITE) != 0 && rp->output.fp != NULL) {
-			if (rp->output.gawk_fflush(rp->output.fp, rp->output.opaque)) {
+			if (rp->output.gawk_fflush(rp->output.fp, rp->output.opaque) != 0) {
 				if ((rp->flag & RED_PIPE) != 0)
 					warning(_("pipe flush of `%s' failed (%s)."),
 						rp->value, strerror(errno));
@@ -2076,7 +2099,7 @@ two_way_open(const char *str, struct redirect *rp, int extfd)
 
 			/* stderr does NOT get dup'ed onto child's stdout */
 
-			signal(SIGPIPE, SIG_DFL);
+			set_sigpipe_to_default();
 
 			execl("/bin/sh", "sh", "-c", str, NULL);
 			_exit(errno == ENOENT ? 127 : 126);
@@ -2253,7 +2276,7 @@ use_pipes:
 		    || close(ctop[0]) == -1 || close(ctop[1]) == -1)
 			fatal(_("close of pipe failed (%s)"), strerror(errno));
 		/* stderr does NOT get dup'ed onto child's stdout */
-		signal(SIGPIPE, SIG_DFL);
+		set_sigpipe_to_default();
 		execl("/bin/sh", "sh", "-c", str, NULL);
 		_exit(errno == ENOENT ? 127 : 126);
 	}
@@ -2490,7 +2513,7 @@ gawk_popen(const char *cmd, struct redirect *rp)
 			fatal(_("moving pipe to stdout in child failed (dup: %s)"), strerror(errno));
 		if (close(p[0]) == -1 || close(p[1]) == -1)
 			fatal(_("close of pipe failed (%s)"), strerror(errno));
-		signal(SIGPIPE, SIG_DFL);
+		set_sigpipe_to_default();
 		execl("/bin/sh", "sh", "-c", cmd, NULL);
 		_exit(errno == ENOENT ? 127 : 126);
 	}
@@ -2555,17 +2578,13 @@ gawk_popen(const char *cmd, struct redirect *rp)
 	FILE *current;
 
 	os_restore_mode(fileno(stdin));
-#ifdef SIGPIPE
-	signal(SIGPIPE, SIG_DFL);
-#endif
+	set_sigpipe_to_default();
 
 	current = popen(cmd, binmode("r"));
 
 	if ((BINMODE & BINMODE_INPUT) != 0)
 		os_setbinmode(fileno(stdin), O_BINARY);
-#ifdef SIGPIPE
-	signal(SIGPIPE, SIG_IGN);
-#endif
+	ignore_sigpipe();
 
 	if (current == NULL)
 		return NULL;
diff --git a/main.c b/main.c
index 56482f51..4f578d3e 100644
--- a/main.c
+++ b/main.c
@@ -255,7 +255,7 @@ main(int argc, char **argv)
 #ifdef SIGBUS
 	(void) signal(SIGBUS, catchsig);
 #endif
-#ifdef SIGPIPE
+
 	/*
 	 * Ignore SIGPIPE so that writes to pipes that fail don't
 	 * kill the process but instead return -1 and set errno.
@@ -269,8 +269,7 @@ main(int argc, char **argv)
 	 * should not give us "broken pipe" messages --- mainly because
 	 * it did not do so in the past and people would complain.
 	 */
-	signal(SIGPIPE, SIG_IGN);
-#endif
+	ignore_sigpipe();
 
 	(void) sigsegv_install_handler(catchsegv);
 #define STACK_SIZE (16*1024)