Clean up some psql issues around handling of the query output file.

Formerly, if "psql -o foo" failed to open the output file "foo", it would
print an error message but then carry on as though -o had not been
specified at all.  This seems contrary to expectation: a program that
cannot open its output file normally fails altogether.  Make psql do
exit(1) after reporting the error.

If "\o foo" failed to open "foo", it would print an error message but then
reset the output file to stdout, as if the argument had been omitted.
This is likewise pretty surprising behavior.  Make it keep the previous
output state, instead.

psql keeps SIGPIPE interrupts disabled when it is writing to a pipe, either
a pipe specified by -o/\o or a transient pipe opened for purposes such as
using a pager on query output.  The logic for this was too simple and could
sometimes re-enable SIGPIPE when a -o pipe was still active, thus possibly
leading to an unexpected psql crash later.

Fixing the last point required getting rid of the kluge in PrintQueryTuples
and ExecQueryUsingCursor whereby they'd transiently change the global
queryFout state, but that seems like good cleanup anyway.

Back-patch to 9.5 but not further; these are minor-enough issues that
changing the behavior in stable branches doesn't seem appropriate.

1 files changed, 99 insertions, 85 deletions

diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index 3254a140b3a..a287eeee195 100644
--- a/src/bin/psql/common.c
+++ b/src/bin/psql/common.c
@@ -26,72 +26,90 @@
 #include "mbprint.h"
 
 
-
 static bool ExecQueryUsingCursor(const char *query, double *elapsed_msec);
 static bool command_no_begin(const char *query);
 static bool is_select_command(const char *query);
 
+
 /*
- * setQFout
- * -- handler for -o command line option and \o command
+ * openQueryOutputFile --- attempt to open a query output file
  *
- * Tries to open file fname (or pipe if fname starts with '|')
- * and stores the file handle in pset)
- * Upon failure, sets stdout and returns false.
+ * fname == NULL selects stdout, else an initial '|' selects a pipe,
+ * else plain file.
+ *
+ * Returns output file pointer into *fout, and is-a-pipe flag into *is_pipe.
+ * Caller is responsible for adjusting SIGPIPE state if it's a pipe.
+ *
+ * On error, reports suitable error message and returns FALSE.
  */
 bool
-setQFout(const char *fname)
+openQueryOutputFile(const char *fname, FILE **fout, bool *is_pipe)
 {
-	bool		status = true;
-
-	/* Close old file/pipe */
-	if (pset.queryFout && pset.queryFout != stdout && pset.queryFout != stderr)
-	{
-		if (pset.queryFoutPipe)
-			pclose(pset.queryFout);
-		else
-			fclose(pset.queryFout);
-	}
-
-	/* If no filename, set stdout */
 	if (!fname || fname[0] == '\0')
 	{
-		pset.queryFout = stdout;
-		pset.queryFoutPipe = false;
+		*fout = stdout;
+		*is_pipe = false;
 	}
 	else if (*fname == '|')
 	{
-		pset.queryFout = popen(fname + 1, "w");
-		pset.queryFoutPipe = true;
+		*fout = popen(fname + 1, "w");
+		*is_pipe = true;
 	}
 	else
 	{
-		pset.queryFout = fopen(fname, "w");
-		pset.queryFoutPipe = false;
+		*fout = fopen(fname, "w");
+		*is_pipe = false;
 	}
 
-	if (!(pset.queryFout))
+	if (*fout == NULL)
 	{
 		psql_error("%s: %s\n", fname, strerror(errno));
-		pset.queryFout = stdout;
-		pset.queryFoutPipe = false;
-		status = false;
+		return false;
 	}
 
-	/* Direct signals */
-#ifndef WIN32
-	pqsignal(SIGPIPE, pset.queryFoutPipe ? SIG_IGN : SIG_DFL);
-#endif
-
-	return status;
+	return true;
 }
 
+/*
+ * setQFout
+ * -- handler for -o command line option and \o command
+ *
+ * On success, updates pset with the new output file and returns true.
+ * On failure, returns false without changing pset state.
+ */
+bool
+setQFout(const char *fname)
+{
+	FILE	   *fout;
+	bool		is_pipe;
+
+	/* First make sure we can open the new output file/pipe */
+	if (!openQueryOutputFile(fname, &fout, &is_pipe))
+		return false;
+
+	/* Close old file/pipe */
+	if (pset.queryFout && pset.queryFout != stdout && pset.queryFout != stderr)
+	{
+		if (pset.queryFoutPipe)
+			pclose(pset.queryFout);
+		else
+			fclose(pset.queryFout);
+	}
+
+	pset.queryFout = fout;
+	pset.queryFoutPipe = is_pipe;
+
+	/* Adjust SIGPIPE handling appropriately: ignore signal if is_pipe */
+	set_sigpipe_trap_state(is_pipe);
+	restore_sigpipe_trap();
+
+	return true;
+}
 
 
 /*
  * Error reporting for scripts. Errors should look like
  *	 psql:filename:lineno: message
- *
  */
 void
 psql_error(const char *fmt,...)
@@ -611,27 +629,23 @@ PrintQueryTuples(const PGresult *results)
 	/* write output to \g argument, if any */
 	if (pset.gfname)
 	{
-		/* keep this code in sync with ExecQueryUsingCursor */
-		FILE	   *queryFout_copy = pset.queryFout;
-		bool		queryFoutPipe_copy = pset.queryFoutPipe;
-
-		pset.queryFout = stdout;	/* so it doesn't get closed */
+		FILE	   *fout;
+		bool		is_pipe;
 
-		/* open file/pipe */
-		if (!setQFout(pset.gfname))
-		{
-			pset.queryFout = queryFout_copy;
-			pset.queryFoutPipe = queryFoutPipe_copy;
+		if (!openQueryOutputFile(pset.gfname, &fout, &is_pipe))
 			return false;
-		}
-
-		printQuery(results, &my_popt, pset.queryFout, false, pset.logfile);
+		if (is_pipe)
+			disable_sigpipe_trap();
 
-		/* close file/pipe, restore old setting */
-		setQFout(NULL);
+		printQuery(results, &my_popt, fout, false, pset.logfile);
 
-		pset.queryFout = queryFout_copy;
-		pset.queryFoutPipe = queryFoutPipe_copy;
+		if (is_pipe)
+		{
+			pclose(fout);
+			restore_sigpipe_trap();
+		}
+		else
+			fclose(fout);
 	}
 	else
 		printQuery(results, &my_popt, pset.queryFout, false, pset.logfile);
@@ -1199,10 +1213,10 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
 	PGresult   *results;
 	PQExpBufferData buf;
 	printQueryOpt my_popt = pset.popt;
-	FILE	   *queryFout_copy = pset.queryFout;
-	bool		queryFoutPipe_copy = pset.queryFoutPipe;
+	FILE	   *fout;
+	bool		is_pipe;
+	bool		is_pager = false;
 	bool		started_txn = false;
-	bool		did_pager = false;
 	int			ntuples;
 	int			fetch_count;
 	char		fetch_cmd[64];
@@ -1268,21 +1282,22 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
 	/* prepare to write output to \g argument, if any */
 	if (pset.gfname)
 	{
-		/* keep this code in sync with PrintQueryTuples */
-		pset.queryFout = stdout;	/* so it doesn't get closed */
-
-		/* open file/pipe */
-		if (!setQFout(pset.gfname))
+		if (!openQueryOutputFile(pset.gfname, &fout, &is_pipe))
 		{
-			pset.queryFout = queryFout_copy;
-			pset.queryFoutPipe = queryFoutPipe_copy;
 			OK = false;
 			goto cleanup;
 		}
+		if (is_pipe)
+			disable_sigpipe_trap();
+	}
+	else
+	{
+		fout = pset.queryFout;
+		is_pipe = false;		/* doesn't matter */
 	}
 
 	/* clear any pre-existing error indication on the output stream */
-	clearerr(pset.queryFout);
+	clearerr(fout);
 
 	for (;;)
 	{
@@ -1302,12 +1317,10 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
 		if (PQresultStatus(results) != PGRES_TUPLES_OK)
 		{
 			/* shut down pager before printing error message */
-			if (did_pager)
+			if (is_pager)
 			{
-				ClosePager(pset.queryFout);
-				pset.queryFout = queryFout_copy;
-				pset.queryFoutPipe = queryFoutPipe_copy;
-				did_pager = false;
+				ClosePager(fout);
+				is_pager = false;
 			}
 
 			OK = AcceptResult(results);
@@ -1331,17 +1344,17 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
 			/* this is the last result set, so allow footer decoration */
 			my_popt.topt.stop_table = true;
 		}
-		else if (pset.queryFout == stdout && !did_pager)
+		else if (fout == stdout && !is_pager)
 		{
 			/*
 			 * If query requires multiple result sets, hack to ensure that
 			 * only one pager instance is used for the whole mess
 			 */
-			pset.queryFout = PageOutput(INT_MAX, &(my_popt.topt));
-			did_pager = true;
+			fout = PageOutput(INT_MAX, &(my_popt.topt));
+			is_pager = true;
 		}
 
-		printQuery(results, &my_popt, pset.queryFout, did_pager, pset.logfile);
+		printQuery(results, &my_popt, fout, is_pager, pset.logfile);
 
 		PQclear(results);
 
@@ -1355,7 +1368,7 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
 		 * the pager dies/exits/etc, there's no sense throwing more data at
 		 * it.
 		 */
-		flush_error = fflush(pset.queryFout);
+		flush_error = fflush(fout);
 
 		/*
 		 * Check if we are at the end, if a cancel was pressed, or if there
@@ -1365,24 +1378,25 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
 		 * stop bothering to pull down more data.
 		 */
 		if (ntuples < fetch_count || cancel_pressed || flush_error ||
-			ferror(pset.queryFout))
+			ferror(fout))
 			break;
 	}
 
-	/* close \g argument file/pipe, restore old setting */
 	if (pset.gfname)
 	{
-		/* keep this code in sync with PrintQueryTuples */
-		setQFout(NULL);
-
-		pset.queryFout = queryFout_copy;
-		pset.queryFoutPipe = queryFoutPipe_copy;
+		/* close \g argument file/pipe */
+		if (is_pipe)
+		{
+			pclose(fout);
+			restore_sigpipe_trap();
+		}
+		else
+			fclose(fout);
 	}
-	else if (did_pager)
+	else if (is_pager)
 	{
-		ClosePager(pset.queryFout);
-		pset.queryFout = queryFout_copy;
-		pset.queryFoutPipe = queryFoutPipe_copy;
+		/* close transient pager */
+		ClosePager(fout);
 	}
 
 cleanup: