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From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 19 Apr 2018 18:16:12 +0800
> ash originally had support for omitting the fork when expanding a
> builtin in backquotes. dash has gradually been removing this support,
> most recently in commit 66b614e29038e31745c4a5d296f64f8d64f5c377
> ("[EVAL] Remove unused EV_BACKCMD flag").
>
> Some traces still remain, however. Remove:
>
> - the buf and nleft elements of the backcmd structure;
> - a misleading comment regarding handling of builtins.
>
> Signed-off-by: Ron Yorston <rmy@xxxxxxxxxxxx>
Unfortunately we may need this at some point in the future due
to changes in POSIX. So let's keep it around for now until we
get things such as `jobs -p` to work.
*************************************
From: Ron Yorston <rmy@xxxxxxxxxxxx>
Date: Thu, 19 Apr 2018 17:18:47 +0100
>Unfortunately we may need this at some point in the future due
>to changes in POSIX. So let's keep it around for now until we
>get things such as `jobs -p` to work.
As you wish.
Something even more trivial I noticed later: the TRACE at the end of
expbackq incorrectly refers to the function as evalbackq.
*************************************
Date: Tue, 10 Apr 2018 13:23:35 +0100
From: Ron Yorston <rmy@pobox.com>
To: busybox@busybox.net
Subject: [PATCH] ash: remove unnecessary code in backquote expansion
Some traces remain of ash's ancient support for omitting the fork when
expanding a builtin command in backquotes.
Remove:
- the buf and nleft elements of the backcmd structure;
- a misleading comment regarding handling of builtins.
I've submitted a similar patch to dash.
Signed-off-by: Ron Yorston <rmy@pobox.com>
---
shell/ash.c | 37 +++++++++----------------------------
1 file changed, 9 insertions(+), 28 deletions(-)
diff --git a/shell/ash.c b/shell/ash.c
index 45c747dbc..6f1458722 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -6356,15 +6356,12 @@ exptilde(char *startp, char *p, int flags)
}
/*
- * Execute a command inside back quotes. If it's a builtin command, we
- * want to save its output in a block obtained from malloc. Otherwise
- * we fork off a subprocess and get the output of the command via a pipe.
- * Should be called with interrupts off.
+ * Execute a command inside back quotes. We fork off a subprocess and
+ * get the output of the command via a pipe. Should be called with
+ * interrupts off.
*/
struct backcmd { /* result of evalbackcmd */
int fd; /* file descriptor to read from */
- int nleft; /* number of chars in buffer */
- char *buf; /* buffer */
struct job *jp; /* job structure for command */
};
@@ -6394,8 +6391,6 @@ evalbackcmd(union node *n, struct backcmd *result)
struct job *jp;
result->fd = -1;
- result->buf = NULL;
- result->nleft = 0;
result->jp = NULL;
if (n == NULL) {
goto out;
@@ -6432,8 +6427,7 @@ evalbackcmd(union node *n, struct backcmd *result)
result->jp = jp;
out:
- TRACE(("evalbackcmd done: fd=%d buf=0x%x nleft=%d jp=0x%x\n",
- result->fd, result->buf, result->nleft, result->jp));
+ TRACE(("evalbackcmd done: fd=%d jp=0x%x\n", result->fd, result->jp));
}
/*
@@ -6445,7 +6439,6 @@ expbackq(union node *cmd, int flag)
struct backcmd in;
int i;
char buf[128];
- char *p;
char *dest;
int startloc;
int syntax = flag & EXP_QUOTED ? DQSYNTAX : BASESYNTAX;
@@ -6457,24 +6450,12 @@ expbackq(union node *cmd, int flag)
evalbackcmd(cmd, &in);
popstackmark(&smark);
- p = in.buf;
- i = in.nleft;
- if (i == 0)
- goto read;
- for (;;) {
- memtodest(p, i, syntax, flag & QUOTES_ESC);
- read:
- if (in.fd < 0)
- break;
- i = nonblock_immune_read(in.fd, buf, sizeof(buf));
- TRACE(("expbackq: read returns %d\n", i));
- if (i <= 0)
- break;
- p = buf;
- }
-
- free(in.buf);
if (in.fd >= 0) {
+ while ((i = nonblock_immune_read(in.fd, buf, sizeof(buf))) > 0) {
+ TRACE(("expbackq: read returns %d\n", i));
+ memtodest(buf, i, syntax, flag & QUOTES_ESC);
+ }
+
close(in.fd);
back_exitstatus = waitforjob(in.jp);
}
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