shithub: riscv

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ref: a48b462e4464c762fac0c8fa0af18d05db2a725f
parent: 0e97c8d1d7dd8dc2ba800656939106721b1d816f
author: cinap_lenrek <cinap_lenrek@felloff.net>
date: Fri May 29 22:03:18 EDT 2020

rc: avoid forking for final command that has variable assignments (to get $apid right)

basically, we want the following commands to print
the same pid twice:

rc -c 'cat /dev/pid &;echo $apid'

vs:

rc -c 'a=1 cat /dev/pid &;echo $apid'

basically, Xsimple() calls exitnext() to determine if
a simple command should be promoted to exec, by peeking
ahead into the code and searching for Xexit instruction.

Xexit might not follow immediately after the Xsimple
instruction because of redirections, which exitnext()
would skip.

but it would not skip the Xunlocal instructions that
where added by the variable assignment.

--- a/sys/src/cmd/rc/simple.c

+++ b/sys/src/cmd/rc/simple.c

@@ -12,7 +12,7 @@

 int

 exitnext(void){

 	union code *c=&runq->code[runq->pc];

-	while(c->f==Xpopredir) c++;

+	while(c->f==Xpopredir || c->f==Xunlocal) c++;

 	return c->f==Xexit;

 }