It's often the case that we simply need the expr's truth value.
To get the value of an expression or simply if we need to know
if it's a constant value we can use some functions like
get_expression_value() or const_expression_value() depending
on the type of warning needed if the expression is not constant
(for various definition of constant).
However none of these functions take in account the fact that
a comma expression can also have a value known at compile time.
In order to not introduce unwanted change elsewheer in the code,
introduce a new function expr_truth_value() which never warn
but will return -1 if the expr have no known boolean value.
Note: the whole set of functions should be unified to take comma
expressions in account when needed.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
expand.c | 30 ++++++++++++++++++++++++++++++
expression.h | 1 +
2 files changed, 31 insertions(+)
diff --git a/expand.c b/expand.c
index 5f908c971..f436b5b50 100644
--- a/expand.c
+++ b/expand.c
@@ -1281,6 +1281,36 @@ long long get_expression_value_silent(struct expression *expr)
return __get_expression_value(expr, 2);
}
+int expr_truth_value(struct expression *expr)
+{
+ const int saved = conservative;
+ struct symbol *ctype;
+
+ if (!expr)
+ return 0;
+
+ ctype = evaluate_expression(expr);
+ if (!ctype)
+ return -1;
+
+ conservative = 1;
+ expand_expression(expr);
+ conservative = saved;
+
+redo:
+ switch (expr->type) {
+ case EXPR_COMMA:
+ expr = expr->right;
+ goto redo;
+ case EXPR_VALUE:
+ return expr->value != 0;
+ case EXPR_FVALUE:
+ return expr->fvalue != 0;
+ default:
+ return -1;
+ }
+}
+
int is_zero_constant(struct expression *expr)
{
const int saved = conservative;
diff --git a/expression.h b/expression.h
index 80b3be5f5..d0f3ac925 100644
--- a/expression.h
+++ b/expression.h
@@ -178,6 +178,7 @@ struct expression {
/* Constant expression values */
int is_zero_constant(struct expression *);
+int expr_truth_value(struct expression *expr);
long long get_expression_value(struct expression *);
long long const_expression_value(struct expression *);
long long get_expression_value_silent(struct expression *expr);
--
2.13.2
--
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