asm: check earlier that body & constraints are strings

The syntax of extended ASM statements requires that the
bodies & constraints are given via a literal string.

However, at parsing time more general expressions are accepted
and it's checked only at evaluation time if these are effectively
string literals. This has at least two drawbacks:
*) evaluate_asm_statement() is slightly more complicated than
   needed, mixing these checks with the real evaluation code
*) in case of error, the diagnostic is issued later than
   other syntaxic warnings.

Fix this by checking at parse-time that ASM bodies & constraints
are string literals and not some arbitrary expressions.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>

3 files changed, 10 insertions, 17 deletions

diff --git a/evaluate.c b/evaluate.c
index 70d76523..634da4b9 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -3523,20 +3523,15 @@ static void evaluate_asm_statement(struct statement *stmt)
 	struct symbol *sym;
 
 	expr = stmt->asm_string;
-	if (!expr || expr->type != EXPR_STRING) {
-		sparse_error(stmt->pos, "need constant string for inline asm");
+	if (!expr)
 		return;
-	}
 
 	FOR_EACH_PTR(stmt->asm_outputs, op) {
 		/* Identifier */
 
 		/* Constraint */
 		expr = op->constraint;
-		if (!expr || expr->type != EXPR_STRING) {
-			sparse_error(expr ? expr->pos : stmt->pos, "asm output constraint is not a string");
-			op->constraint = NULL;
-		} else
+		if (expr)
 			verify_output_constraint(expr, expr->string->data);
 
 		/* Expression */
@@ -3553,10 +3548,7 @@ static void evaluate_asm_statement(struct statement *stmt)
 
 		/* Constraint */
 		expr = op->constraint;
-		if (!expr || expr->type != EXPR_STRING) {
-			sparse_error(expr ? expr->pos : stmt->pos, "asm input constraint is not a string");
-			op->constraint = NULL;
-		} else
+		if (expr)
 			verify_input_constraint(expr, expr->string->data);
 
 		/* Expression */
diff --git a/parse.c b/parse.c
index 401f91a1..23c0ee01 100644
--- a/parse.c
+++ b/parse.c
@@ -2050,7 +2050,8 @@ static struct token *parse_asm_operands(struct token *token, struct statement *s
 			op->name = token->next->next->ident;
 			token = token->next->next->next;
 		}
-		token = primary_expression(token->next, &op->constraint);
+		token = token->next;
+		token = string_expression(token, &op->constraint, "asm constraint");
 		token = parens_expression(token, &op->expr, "in asm parameter");
 		add_expression(inout, op);
 	} while (match_op(token, ','));
@@ -2101,7 +2102,7 @@ static struct token *parse_asm_statement(struct token *token, struct statement *
 		token = token->next;
 	}
 	token = expect(token, '(', "after asm");
-	token = parse_expression(token, &stmt->asm_string);
+	token = string_expression(token, &stmt->asm_string, "inline asm");
 	if (match_op(token, ':'))
 		token = parse_asm_operands(token, stmt, &stmt->asm_outputs);
 	if (match_op(token, ':'))
@@ -2118,7 +2119,7 @@ static struct token *parse_asm_declarator(struct token *token, struct decl_state
 {
 	struct expression *expr;
 	token = expect(token, '(', "after asm");
-	token = parse_expression(token->next, &expr);
+	token = string_expression(token, &expr, "inline asm");
 	token = expect(token, ')', "after asm");
 	return token;
 }
diff --git a/validation/asm-bad0.c b/validation/asm-bad0.c
index fcd9b1c4..aa9bf28d 100644
--- a/validation/asm-bad0.c
+++ b/validation/asm-bad0.c
@@ -30,12 +30,12 @@ static void iexpr(void)
  * check-name: asm-bad0
  *
  * check-error-start
+asm-bad0.c:6:13: error: string literal expected for inline asm
+asm-bad0.c:11:32: error: string literal expected for asm constraint
+asm-bad0.c:16:49: error: string literal expected for asm constraint
 asm-bad0.c:21:41: error: Expected ] at end of array dereference
 asm-bad0.c:21:41: error: got )
 asm-bad0.c:26:59: error: Expected ] at end of array dereference
 asm-bad0.c:26:59: error: got )
-asm-bad0.c:6:9: error: need constant string for inline asm
-asm-bad0.c:11:32: error: asm output constraint is not a string
-asm-bad0.c:16:49: error: asm input constraint is not a string
  * check-error-end
  */