sh: Save/restore changed variables in optimized command substitution.

In optimized command substitution, save and restore any variables changed by
expansions (${var=value} and $((var=assigned))), instead of trying to
determine if an expansion may cause such changes.

If $! is referenced in optimized command substitution, do not cause jobs to
be remembered longer.

This fixes $(jobs $!) again, simplifies the man page and shortens the code.

1 files changed, 0 insertions, 72 deletions

diff --git a/bin/sh/expand.c b/bin/sh/expand.c
index beb655d..c6c54ab 100644
--- a/bin/sh/expand.c
+++ b/bin/sh/expand.c
@@ -1621,78 +1621,6 @@ cvtnum(int num, char *buf)
 }
 
 /*
- * Check statically if expanding a string may have side effects.
- */
-int
-expandhassideeffects(const char *p)
-{
-	int c;
-	int arinest;
-
-	arinest = 0;
-	while ((c = *p++) != '\0') {
-		switch (c) {
-		case CTLESC:
-			p++;
-			break;
-		case CTLVAR:
-			c = *p++;
-			/* Expanding $! sets the job to remembered. */
-			if (*p == '!')
-				return 1;
-			if ((c & VSTYPE) == VSASSIGN)
-				return 1;
-			/*
-			 * If we are in arithmetic, the parameter may contain
-			 * '=' which may cause side effects. Exceptions are
-			 * the length of a parameter and $$, $# and $? which
-			 * are always numeric.
-			 */
-			if ((c & VSTYPE) == VSLENGTH) {
-				while (*p != '=')
-					p++;
-				p++;
-				break;
-			}
-			if ((*p == '$' || *p == '#' || *p == '?') &&
-			    p[1] == '=') {
-				p += 2;
-				break;
-			}
-			if (arinest > 0)
-				return 1;
-			break;
-		case CTLBACKQ:
-		case CTLBACKQ | CTLQUOTE:
-			if (arinest > 0)
-				return 1;
-			break;
-		case CTLARI:
-			arinest++;
-			break;
-		case CTLENDARI:
-			arinest--;
-			break;
-		case '=':
-			if (*p == '=') {
-				/* Allow '==' operator. */
-				p++;
-				continue;
-			}
-			if (arinest > 0)
-				return 1;
-			break;
-		case '!': case '<': case '>':
-			/* Allow '!=', '<=', '>=' operators. */
-			if (*p == '=')
-				p++;
-			break;
-		}
-	}
-	return 0;
-}
-
-/*
  * Do most of the work for wordexp(3).
  */