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commit    9eb2503391da1d0a17d3116a5a49e4f73b1af84f
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Wed Oct 28 18:35:53 2020 +0000
First released in: 14.0, 9.5.24, 9.6.20, 10.15, 11.10, 12.5, 13.1

    Use mode "r" for popen() in psql's evaluate_backtick().
    
    In almost all other places, we use plain "r" or "w" mode in popen()
    calls (the exceptions being for COPY data).  This one has been
    overlooked (possibly because it's buried in a ".l" flex file?),
    but it's using PG_BINARY_R.
    
    Kensuke Okamura complained in bug #16688 that we fail to strip \r
    when stripping the trailing newline from a backtick result string.
    That's true enough, but we'd also fail to convert embedded \r\n
    cleanly, which also seems undesirable.  Fixing the popen() mode
    seems like the best way to deal with this.
    
    It's been like this for a long time, so back-patch to all supported
    branches.
    
    Discussion: https://postgr.es/m/16688-c649c7b69cd7e6f8@postgresql.org


 src/bin/psql/psqlscanslash.l | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/bin/psql/psqlscanslash.l b/src/bin/psql/psqlscanslash.l
index 34df35e5f43..2567ed80809 100644
--- a/src/bin/psql/psqlscanslash.l
+++ b/src/bin/psql/psqlscanslash.l
@@ -776,7 +776,7 @@ evaluate_backtick(PsqlScanState state)
 
 	initPQExpBuffer(&cmd_output);
 
-	fd = popen(cmd, PG_BINARY_R);
+	fd = popen(cmd, "r");
 	if (!fd)
 	{
 		state->callbacks->write_error("%s: %s\n", cmd, strerror(errno));
@@ -817,7 +817,7 @@ evaluate_backtick(PsqlScanState state)
 	/* If no error, transfer result to output_buf */
 	if (!error)
 	{
-		/* strip any trailing newline */
+		/* strip any trailing newline (but only one) */
 		if (cmd_output.len > 0 &&
 			cmd_output.data[cmd_output.len - 1] == '\n')
 			cmd_output.len--;


[parent: 66c036b4f143]