sh: Reduce unnecessary forks with eval.

The eval special builtin now runs the code with EV_EXIT if it was run
with EV_EXIT itself.

In particular, this eliminates one fork when a command substitution contains
an eval command that ends with an external program or a subshell.

This is similar to what r220978 did for functions.

1 files changed, 2 insertions, 1 deletions

diff --git a/bin/sh/eval.c b/bin/sh/eval.c
index 9d67b9e..25793c1 100644
--- a/bin/sh/eval.c
+++ b/bin/sh/eval.c
@@ -140,7 +140,7 @@ evalcmd(int argc, char **argv)
                         STPUTC('\0', concat);
                         p = grabstackstr(concat);
                 }
-                evalstring(p, builtin_flags & EV_TESTED);
+                evalstring(p, builtin_flags);
         } else
                 exitstatus = 0;
         return exitstatus;
@@ -908,6 +908,7 @@ evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
 				dup2(pip[1], 1);
 				close(pip[1]);
 			}
+			flags &= ~EV_BACKCMD;
 		}
 		flags |= EV_EXIT;
 	}