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

From: Josh Poimboeuf
Date: Wed Jan 24 2018 - 15:54:17 EST


On Tue, Jan 23, 2018 at 07:38:37PM -0500, Arvind Sankar wrote:
> 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@xxxxxxxxxxxx>

Looks good to me.

Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

Libsubcmd is used by perf and objtool, so adding the perf maintainers to
CC. Arnaldo, do you want to pick this one up?

> ---
> tools/lib/subcmd/pager.c | 17 -----------------
> tools/lib/subcmd/run-command.c | 2 --
> tools/lib/subcmd/run-command.h | 1 -
> 3 files changed, 20 deletions(-)
>
> diff --git a/tools/lib/subcmd/pager.c b/tools/lib/subcmd/pager.c
> index 5ba754d17952..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>
> @@ -23,21 +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_ZERO(&in);
> - FD_SET(0, &in);
> - select(1, &in, NULL, &in, NULL);
> -
> - setenv("LESS", "FRSX", 0);
> -}
> -
> static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
> static struct child_process pager_process;
>
> @@ -84,7 +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
>

--
Josh