expand: remove unnecessary code in backquote expansion

Commit Message

Ron Yorston April 10, 2018, 12:23 p.m. UTC

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 <[e-mail]>
---
 src/eval.c   | 12 ++++--------
 src/eval.h   |  2 --
 src/expand.c | 31 ++++++++++---------------------
 3 files changed, 14 insertions(+), 31 deletions(-)

Comments

Herbert Xu April 19, 2018, 10:16 a.m. UTC | #1

Ron Yorston <[e-mail]> wrote:
> 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 <[e-mail]>

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.

Thanks,

Ron Yorston April 19, 2018, 4:18 p.m. UTC | #2

Herbert Xu <[e-mail]> wrote:
>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.

Ron
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Patch

diff --git a/src/eval.c b/src/eval.c
index 7498f9d..32fc300 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -605,10 +605,9 @@  evalpipe(union node *n, 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.
  */
 
 void
@@ -618,8 +617,6 @@  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;
@@ -644,8 +641,7 @@  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));
 }
 
 static char **
diff --git a/src/eval.h b/src/eval.h
index 63e7d86..92227af 100644
--- a/src/eval.h
+++ b/src/eval.h
@@ -42,8 +42,6 @@  extern int savestatus;		/* exit status of last command outside traps */
 
 struct backcmd {		/* result of evalbackcmd */
 	int fd;			/* file descriptor to read from */
-	char *buf;		/* buffer */
-	int nleft;		/* number of chars in buffer */
 	struct job *jp;		/* job structure for command */
 };
 
diff --git a/src/expand.c b/src/expand.c
index 30288db..04a3eeb 100644
--- a/src/expand.c
+++ b/src/expand.c
@@ -510,7 +510,6 @@  expbackq(union node *cmd, int flag)
 	struct backcmd in;
 	int i;
 	char buf[128];
-	char *p;
 	char *dest;
 	int startloc;
 	char const *syntax = flag & EXP_QUOTED ? DQSYNTAX : BASESYNTAX;
@@ -522,27 +521,17 @@  expbackq(union node *cmd, int flag)
 	evalbackcmd(cmd, (struct backcmd *) &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;
-		do {
-			i = read(in.fd, buf, sizeof buf);
-		} while (i < 0 && errno == EINTR);
-		TRACE(("expbackq: read returns %d\n", i));
-		if (i <= 0)
-			break;
-		p = buf;
-	}
-
-	if (in.buf)
-		ckfree(in.buf);
 	if (in.fd >= 0) {
+		for (;;) {
+			do {
+				i = read(in.fd, buf, sizeof buf);
+			} while (i < 0 && errno == EINTR);
+			TRACE(("expbackq: read returns %d\n", i));
+			if (i <= 0)
+				break;
+			memtodest(buf, i, syntax, flag & QUOTES_ESC);
+		}
+
 		close(in.fd);
 		back_exitstatus = waitforjob(in.jp);
 	}