1 files changed, 72 insertions, 0 deletions
diff --git a/bin/sh/expand.c b/bin/sh/expand.c
index b03cc3b..b2046cc 100644
--- a/bin/sh/expand.c
+++ b/bin/sh/expand.c
@@ -1570,6 +1570,78 @@ 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).
  */