ash: save Ron's patch from oblivion

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 135 insertions, 0 deletions

diff --git a/shell/ash_remove_unnecessary_code_in_backquote_expansion.patch b/shell/ash_remove_unnecessary_code_in_backquote_expansion.patch
new file mode 100644
index 000000000..06067dde0
--- /dev/null
+++ b/shell/ash_remove_unnecessary_code_in_backquote_expansion.patch
@@ -0,0 +1,135 @@
+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);
+        }