linux-kernel - Re: [PATCH] tools: libsubcmd: Drop the less hack that was inherited from Git.

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Message-ID: <20180209000009.GA54330@rani.riverdale>
Date:   Thu, 8 Feb 2018 19:00:10 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] tools: libsubcmd: Drop the less hack that was inherited
 from Git.

We inherited this hack with the original code from the Git project. The
select call is invalid as the two fd_set pointers should not be aliased.

We could fix it, but the Git project removed this hack in 2012 in commit
e8320f3 (pager: drop "wait for output to run less" hack). The bug it
worked around was apparently fixed in less back in June 2007.

So remove the hack from here as well.

Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
---
 - Merge with commit ad343a98 (tools/lib/subcmd/pager.c: do not alias
   select() params) by Sergey

 tools/lib/subcmd/pager.c       | 20 --------------------
 tools/lib/subcmd/run-command.c |  2 --
 tools/lib/subcmd/run-command.h |  1 -
 3 files changed, 23 deletions(-)

diff --git a/tools/lib/subcmd/pager.c b/tools/lib/subcmd/pager.c
index 9997a8805a82..94d61d9b511f 100644
--- a/tools/lib/subcmd/pager.c
+++ b/tools/lib/subcmd/pager.c
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-#include <sys/select.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
@@ -23,24 +22,6 @@ void pager_init(const char *pager_env)
 	subcmd_config.pager_env = pager_env;
 }
 
-static void pager_preexec(void)
-{
-	/*
-	 * Work around bug in "less" by not starting it until we
-	 * have real input
-	 */
-	fd_set in;
-	fd_set exception;
-
-	FD_ZERO(&in);
-	FD_ZERO(&exception);
-	FD_SET(0, &in);
-	FD_SET(0, &exception);
-	select(1, &in, NULL, &exception, NULL);
-
-	setenv("LESS", "FRSX", 0);
-}
-
 static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
 static struct child_process pager_process;
 
@@ -87,7 +68,6 @@ void setup_pager(void)
 	pager_argv[2] = pager;
 	pager_process.argv = pager_argv;
 	pager_process.in = -1;
-	pager_process.preexec_cb = pager_preexec;
 
 	if (start_command(&pager_process))
 		return;
diff --git a/tools/lib/subcmd/run-command.c b/tools/lib/subcmd/run-command.c
index 5cdac2162532..9e9dca717ed7 100644
--- a/tools/lib/subcmd/run-command.c
+++ b/tools/lib/subcmd/run-command.c
@@ -120,8 +120,6 @@ int start_command(struct child_process *cmd)
 					unsetenv(*cmd->env);
 			}
 		}
-		if (cmd->preexec_cb)
-			cmd->preexec_cb();
 		if (cmd->exec_cmd) {
 			execv_cmd(cmd->argv);
 		} else {
diff --git a/tools/lib/subcmd/run-command.h b/tools/lib/subcmd/run-command.h
index 17d969c6add3..6256268802b5 100644
--- a/tools/lib/subcmd/run-command.h
+++ b/tools/lib/subcmd/run-command.h
@@ -46,7 +46,6 @@ struct child_process {
 	unsigned no_stderr:1;
 	unsigned exec_cmd:1; /* if this is to be external sub-command */
 	unsigned stdout_to_stderr:1;
-	void (*preexec_cb)(void);
 };
 
 int start_command(struct child_process *);
-- 
2.13.6