From: Brandon Williams <bmwill@google.com>
To: Jonathan Nieder <jrnieder@gmail.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 4/5] run-command: prepare child environment before forking
Date: Tue, 11 Apr 2017 10:27:09 -0700 [thread overview]
Message-ID: <20170411172709.GE36152@google.com> (raw)
In-Reply-To: <20170411005816.GK8741@aiede.mtv.corp.google.com>
On 04/10, Jonathan Nieder wrote:
> Brandon Williams wrote:
>
> > In order to avoid allocation between 'fork()' and 'exec()' prepare the
> > environment to be used in the child process prior to forking.
>
> If using something like posix_spawn(), this would be needed anyway, so
> I'll review it.
>
> [...]
> > +++ b/run-command.c
> [...]
> > +static char **prep_childenv(const char *const *deltaenv)
> > +{
> > + char **childenv;
> > + int childenv_nr = 0, childenv_alloc = 0;
> > + int i;
> > +
> > + for (i = 0; environ[i]; i++)
> > + childenv_nr++;
> > + for (i = 0; deltaenv && deltaenv[i]; i++)
> > + childenv_alloc++;
> > + /* Add one for the NULL termination */
> > + childenv_alloc += childenv_nr + 1;
> > +
> > + childenv = xcalloc(childenv_alloc, sizeof(char *));
> > + memcpy(childenv, environ, childenv_nr * sizeof(char *));
> > +
> > + /* merge in deltaenv */
> > + for (i = 0; deltaenv && deltaenv[i]; i++)
> > + childenv_nr = do_putenv(childenv, childenv_nr, deltaenv[i]);
> > +
> > + return childenv;
> > +}
>
> This potentially copies around most of 'environ' several times as it
> adjusts for each deltaenv item. Can it be simplified? E.g.
The only time it copies anything is that first memcpy which makes a
duplicate of the environ, and then when an item is being removed in
do_putenv it will move the back of the array to fill in for the entry
being removed.
>
> struct argv_array result = ARGV_ARRAY_INIT;
> struct string_list mods = STRING_LIST_INIT_DUP;
> struct strbuf key = STRBUF_INIT;
> const char **p;
>
> for (p = cmd_env; *p; p++) {
> const char *equals = strchr(*p, '=');
> if (equals) {
> strbuf_reset(&key);
> strbuf_add(&key, *p, equals - *p);
> string_list_append(&mods, key.buf)->util = *p;
> } else {
> string_list_append(&mods, *p);
> }
> }
> string_list_sort(&mods);
>
> for (p = environ; *p; p++) {
> struct string_list_item *item;
> const char *equals = strchr(*p, '=');
> if (!equals)
> continue;
> strbuf_reset(&key);
> strbuf_add(&key, *p, equals - *p);
> item = string_list_lookup(&mods, key.buf);
>
> if (!item) /* no change */
> argv_array_push(&result, *p);
> else if (!item->util) /* unsetenv */
> ; /* skip */
> else /* setenv */
> argv_array_push(&result, item->util);
> }
>
> strbuf_release(&key);
> string_list_clear(&mods);
> return argv_array_detach(&result);
This is probably still incomplete as I don't see how this accounts for
entries in 'cmd_env' which are being added to the environment and not
just replacing existing ones.
--
Brandon Williams
next prev parent reply other threads:[~2017-04-11 17:27 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-10 23:49 [PATCH 0/5] forking and threading Brandon Williams
2017-04-10 23:49 ` [PATCH 1/5] run-command: convert sane_execvp to sane_execvpe Brandon Williams
2017-04-12 19:22 ` Brandon Williams
2017-04-10 23:49 ` [PATCH 2/5] run-command: prepare argv before forking Brandon Williams
2017-04-10 23:49 ` [PATCH 3/5] run-command: allocate child_err " Brandon Williams
2017-04-10 23:49 ` [PATCH 4/5] run-command: prepare child environment " Brandon Williams
2017-04-11 0:58 ` Jonathan Nieder
2017-04-11 17:27 ` Brandon Williams [this message]
2017-04-11 17:30 ` Jonathan Nieder
2017-04-10 23:49 ` [PATCH 5/5] run-command: add note about forking and threading Brandon Williams
2017-04-11 0:26 ` Jonathan Nieder
2017-04-11 0:53 ` Eric Wong
2017-04-11 17:33 ` Jonathan Nieder
2017-04-11 17:34 ` Brandon Williams
2017-04-11 17:40 ` Eric Wong
2017-04-11 7:05 ` [PATCH 6/5] run-command: avoid potential dangers in forked child Eric Wong
2017-04-11 16:29 ` Brandon Williams
2017-04-11 16:59 ` Eric Wong
2017-04-11 17:17 ` Brandon Williams
2017-04-11 17:37 ` [PATCH 0/5] forking and threading Jonathan Nieder
2017-04-11 17:54 ` Brandon Williams
2017-04-13 18:32 ` [PATCH v2 0/6] " Brandon Williams
2017-04-13 18:32 ` [PATCH v2 1/6] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-13 20:43 ` Jonathan Nieder
2017-04-13 20:59 ` Eric Wong
2017-04-13 21:35 ` Brandon Williams
2017-04-13 21:39 ` Eric Wong
2017-04-13 18:32 ` [PATCH v2 2/6] run-command: prepare command before forking Brandon Williams
2017-04-13 21:14 ` Jonathan Nieder
2017-04-13 22:41 ` Brandon Williams
2017-04-13 18:32 ` [PATCH v2 3/6] run-command: prepare child environment " Brandon Williams
2017-04-13 18:32 ` [PATCH v2 4/6] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-13 19:29 ` Eric Wong
2017-04-13 19:43 ` Brandon Williams
2017-04-13 18:32 ` [PATCH v2 5/6] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-13 18:32 ` [PATCH v2 6/6] run-command: add note about forking and threading Brandon Williams
2017-04-13 20:50 ` [PATCH v2 0/6] " Jonathan Nieder
2017-04-13 23:44 ` Brandon Williams
2017-04-13 21:14 ` [PATCH 7/6] run-command: block signals between fork and execve Eric Wong
2017-04-13 23:37 ` Brandon Williams
2017-04-14 2:42 ` Brandon Williams
2017-04-14 5:26 ` Eric Wong
2017-04-14 5:35 ` Eric Wong
2017-04-14 16:58 ` [PATCH v3 00/10] forking and threading Brandon Williams
2017-04-14 16:58 ` [PATCH v3 01/10] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-14 16:58 ` [PATCH v3 02/10] t0061: run_command executes scripts without a #! line Brandon Williams
2017-04-14 16:58 ` [PATCH v3 03/10] run-command: prepare command before forking Brandon Williams
2017-04-14 16:58 ` [PATCH v3 04/10] run-command: use the async-signal-safe execv instead of execvp Brandon Williams
2017-04-14 16:58 ` [PATCH v3 05/10] run-command: prepare child environment before forking Brandon Williams
2017-04-14 16:58 ` [PATCH v3 06/10] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-14 19:38 ` Eric Wong
2017-04-14 20:19 ` Brandon Williams
2017-04-14 16:58 ` [PATCH v3 07/10] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-14 18:50 ` Eric Wong
2017-04-14 20:22 ` Brandon Williams
2017-04-14 16:59 ` [PATCH v3 08/10] run-command: handle dup2 and close errors " Brandon Williams
2017-04-14 16:59 ` [PATCH v3 09/10] run-command: add note about forking and threading Brandon Williams
2017-04-14 16:59 ` [PATCH v3 10/10] run-command: block signals between fork and execve Brandon Williams
2017-04-14 20:24 ` Brandon Williams
2017-04-14 21:35 ` Eric Wong
2017-04-17 22:08 ` [PATCH v4 00/10] forking and threading Brandon Williams
2017-04-17 22:08 ` [PATCH v4 01/10] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-17 22:08 ` [PATCH v4 02/10] t0061: run_command executes scripts without a #! line Brandon Williams
2017-04-17 22:08 ` [PATCH v4 03/10] run-command: prepare command before forking Brandon Williams
2017-04-17 22:08 ` [PATCH v4 04/10] run-command: use the async-signal-safe execv instead of execvp Brandon Williams
2017-04-17 22:08 ` [PATCH v4 05/10] run-command: prepare child environment before forking Brandon Williams
2017-04-18 0:26 ` Eric Wong
2017-04-18 21:02 ` Brandon Williams
2017-04-17 22:08 ` [PATCH v4 06/10] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-17 22:08 ` [PATCH v4 07/10] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-17 22:08 ` [PATCH v4 08/10] run-command: handle dup2 and close errors " Brandon Williams
2017-04-17 22:08 ` [PATCH v4 09/10] run-command: add note about forking and threading Brandon Williams
2017-04-17 22:08 ` [PATCH v4 10/10] run-command: block signals between fork and execve Brandon Williams
2017-04-18 23:17 ` [PATCH v5 00/11] forking and threading Brandon Williams
2017-04-18 23:17 ` [PATCH v5 01/11] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-18 23:17 ` [PATCH v5 02/11] t0061: run_command executes scripts without a #! line Brandon Williams
2017-04-19 5:43 ` Johannes Sixt
2017-04-19 6:21 ` Johannes Sixt
2017-04-19 15:56 ` Brandon Williams
2017-04-19 18:18 ` Johannes Sixt
2017-04-20 10:47 ` Johannes Schindelin
2017-04-20 17:02 ` Brandon Williams
2017-04-20 20:24 ` Johannes Schindelin
2017-04-20 20:49 ` Brandon Williams
2017-04-18 23:17 ` [PATCH v5 03/11] run-command: prepare command before forking Brandon Williams
2017-04-18 23:17 ` [PATCH v5 04/11] run-command: use the async-signal-safe execv instead of execvp Brandon Williams
2017-04-18 23:17 ` [PATCH v5 05/11] string-list: add string_list_remove function Brandon Williams
2017-04-18 23:31 ` Stefan Beller
2017-04-18 23:36 ` Brandon Williams
2017-04-18 23:40 ` Stefan Beller
2017-04-18 23:18 ` [PATCH v5 06/11] run-command: prepare child environment before forking Brandon Williams
2017-04-18 23:18 ` [PATCH v5 07/11] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-18 23:18 ` [PATCH v5 08/11] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-18 23:18 ` [PATCH v5 09/11] run-command: handle dup2 and close errors " Brandon Williams
2017-04-18 23:18 ` [PATCH v5 10/11] run-command: add note about forking and threading Brandon Williams
2017-04-18 23:18 ` [PATCH v5 11/11] run-command: block signals between fork and execve Brandon Williams
2017-04-19 6:00 ` Johannes Sixt
2017-04-19 7:48 ` Eric Wong
2017-04-19 16:10 ` Brandon Williams
2017-04-19 23:13 ` [PATCH v6 00/11] forking and threading Brandon Williams
2017-04-19 23:13 ` [PATCH v6 01/11] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-19 23:13 ` [PATCH v6 02/11] t0061: run_command executes scripts without a #! line Brandon Williams
2017-04-20 10:49 ` Johannes Schindelin
2017-04-20 16:58 ` Brandon Williams
2017-04-19 23:13 ` [PATCH v6 03/11] run-command: prepare command before forking Brandon Williams
2017-04-19 23:13 ` [PATCH v6 04/11] run-command: use the async-signal-safe execv instead of execvp Brandon Williams
2017-05-17 2:15 ` Junio C Hamano
2017-05-17 2:26 ` Jeff King
2017-05-17 2:28 ` Jeff King
2017-05-17 3:41 ` Junio C Hamano
2017-05-17 14:52 ` Brandon Williams
2017-04-19 23:13 ` [PATCH v6 05/11] string-list: add string_list_remove function Brandon Williams
2017-04-19 23:13 ` [PATCH v6 06/11] run-command: prepare child environment before forking Brandon Williams
2017-04-19 23:13 ` [PATCH v6 07/11] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-19 23:13 ` [PATCH v6 08/11] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-19 23:13 ` [PATCH v6 09/11] run-command: handle dup2 and close errors " Brandon Williams
2017-04-19 23:13 ` [PATCH v6 10/11] run-command: add note about forking and threading Brandon Williams
2017-04-19 23:13 ` [PATCH v6 11/11] run-command: block signals between fork and execve Brandon Williams
2017-04-24 22:37 ` [PATCH v6 00/11] forking and threading Brandon Williams
2017-04-24 23:50 ` [PATCH v6 12/11] run-command: don't try to execute directories Brandon Williams
2017-04-25 0:17 ` Jonathan Nieder
2017-04-25 1:58 ` Junio C Hamano
2017-04-25 2:51 ` Jonathan Nieder
2017-04-25 2:56 ` Jeff King
2017-04-25 1:47 ` Junio C Hamano
2017-04-25 2:57 ` Jonathan Nieder
2017-04-25 17:54 ` [PATCH v7 1/2] exec_cmd: expose is_executable function Brandon Williams
2017-04-25 17:54 ` [PATCH v7 2/2] run-command: don't try to execute directories Brandon Williams
2017-04-25 18:51 ` Jonathan Nieder
2017-04-25 19:32 ` Brandon Williams
2017-04-25 18:04 ` [PATCH v7 1/2] exec_cmd: expose is_executable function Jonathan Nieder
2017-04-25 18:18 ` Johannes Sixt
2017-04-25 18:38 ` Brandon Williams
2017-04-25 23:46 ` [PATCH v8 1/2] run-command: " Brandon Williams
2017-04-25 23:47 ` [PATCH v8 2/2] run-command: restrict PATH search to executable files Brandon Williams
2017-04-25 23:50 ` Jonathan Nieder
2017-04-26 1:44 ` Junio C Hamano
2017-04-26 17:10 ` [PATCH v9 " Brandon Williams
2017-04-27 0:33 ` Junio C Hamano
2017-04-25 23:48 ` [PATCH v8 1/2] run-command: expose is_executable function Jonathan Nieder
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