When expanding those builtins, we directly excludes a non-constant
arg (via the expression expansion cost) and the to retrieve the
value we use const_expression_value().
But const_expression_value() is to be used for expressions that
qualify as 'integer constant expression' as per the C standard.
However we want to be able to use this builtin with all integer
expressions having a known value at compile time, even those
not qualified as true 'integer constant expression'.
Fix this by using get_expression_value_silent() instead of
const_expression_value().
Note: this bug was found by testing sparse on the git tree
on ARM64.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
builtin.c | 4 +++-
validation/builtin-bswap-constant.c | 6 ++++++
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/builtin.c b/builtin.c
index dbb81032b..4f2a106cb 100644
--- a/builtin.c
+++ b/builtin.c
@@ -179,13 +179,15 @@ static struct symbol_op choose_op = {
/* The argument is constant and valid if the cost is zero */
static int expand_bswap(struct expression *expr, int cost)
{
+ struct expression *arg;
long long val;
if (cost)
return cost;
/* the arguments number & type have already been checked */
- val = const_expression_value(first_expression(expr->args));
+ arg = first_expression(expr->args);
+ val = get_expression_value_silent(arg);
switch (expr->ctype->bit_size) {
case 16: expr->value = __builtin_bswap16(val); break;
case 32: expr->value = __builtin_bswap32(val); break;
diff --git a/validation/builtin-bswap-constant.c b/validation/builtin-bswap-constant.c
index 4560f67e9..18574d4c5 100644
--- a/validation/builtin-bswap-constant.c
+++ b/validation/builtin-bswap-constant.c
@@ -16,6 +16,12 @@ unsigned long long bswap64(void)
return __builtin_bswap64(0x123456789abcdef0ULL);
}
+unsigned int half_constant(void);
+unsigned int half_constant(void)
+{
+ int v = 0x12345678;
+ return __builtin_bswap32(v);
+}
/*
* check-name: builtin-bswap-constant
* check-command: test-linearize $file
--
2.13.0
--
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