sh: Fix some bugs with backquoted builtins:

- correctly handle error output in $(builtin 2>&1), clarify out1/out2 vs
  output/errout in the code
- treat all builtins as regular builtins so errors do not abort the shell
  and variable assignments do not persist
- respect the caller's INTOFF

Some bugs still exist:
- expansion errors may still abort the shell
- some side effects of expansions and builtins persist

1 files changed, 12 insertions, 11 deletions

diff --git a/bin/sh/eval.c b/bin/sh/eval.c
index e54d19a..f2caafb 100644
--- a/bin/sh/eval.c
+++ b/bin/sh/eval.c
@@ -646,7 +646,7 @@ evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
 		out2str(ps4val());
 		for (sp = varlist.list ; sp ; sp = sp->next) {
 			if (sep != 0)
-				outc(' ', &errout);
+				out2c(' ');
 			p = sp->text;
 			while (*p != '=' && *p != '\0')
 				out2c(*p++);
@@ -658,7 +658,7 @@ evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
 		}
 		for (sp = arglist.list ; sp ; sp = sp->next) {
 			if (sep != 0)
-				outc(' ', &errout);
+				out2c(' ');
 			/* Disambiguate command looking like assignment. */
 			if (sp == arglist.list &&
 					strchr(sp->text, '=') != NULL &&
@@ -670,7 +670,7 @@ evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
 				out2qstr(sp->text);
 			sep = ' ';
 		}
-		outc('\n', &errout);
+		out2c('\n');
 		flushout(&errout);
 	}
 
@@ -722,9 +722,8 @@ evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
 					break;
 				if ((cmdentry.u.index = find_builtin(*argv,
 				    &cmdentry.special)) < 0) {
-					outfmt(&errout, "%s: not found\n", *argv);
+					out2fmt_flush("%s: not found\n", *argv);
 					exitstatus = 127;
-					flushout(&errout);
 					return;
 				}
 				if (cmdentry.u.index != BLTINCMD)
@@ -832,6 +831,7 @@ evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
 			memout.nextc = memout.buf;
 			memout.bufsize = 64;
 			mode |= REDIR_BACKQ;
+			cmdentry.special = 0;
 		}
 		savecmdname = commandname;
 		savetopfile = getcurrentfile();
@@ -865,20 +865,21 @@ cmddone:
 			}
 		}
 		handler = savehandler;
+		if (flags == EV_BACKCMD) {
+			backcmd->buf = memout.buf;
+			backcmd->nleft = memout.nextc - memout.buf;
+			memout.buf = NULL;
+		}
 		if (e != -1) {
 			if ((e != EXERROR && e != EXEXEC)
 			    || cmdentry.special)
 				exraise(e);
 			popfilesupto(savetopfile);
-			FORCEINTON;
+			if (flags != EV_BACKCMD)
+				FORCEINTON;
 		}
 		if (cmdentry.u.index != EXECCMD)
 			popredir();
-		if (flags == EV_BACKCMD) {
-			backcmd->buf = memout.buf;
-			backcmd->nleft = memout.nextc - memout.buf;
-			memout.buf = NULL;
-		}
 	} else {
 #ifdef DEBUG
 		trputs("normal command:  ");  trargs(argv);