If you dereference a function pointer, you get a function pointer back.
AFAICS there are >=69 places in the kernel that unnecessarily dereference a
function pointer before calling through it.
Output of testcase when applied to previous version:
=============================================
$ ./test-suite single linear/fn-ptr-deref.c
TEST dereference function pointer (linear/fn-ptr-deref.c)
error: actual output text does not match expected output text.
error: see linear/fn-ptr-deref.c.output.* for further investigation.
--- linear/fn-ptr-deref.c.output.expected 2018-02-22 01:26:20.592985408 +0100
+++ linear/fn-ptr-deref.c.output.got 2018-02-22 01:26:20.588985440 +0100
@@ -2,7 +2,8 @@
.L0:
<entry-point>
call func_a
- call func_a
+ load %r4 <- 0[func_a]
+ call VOID
ret
linear/fn-ptr-deref.c failed !
=============================================
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
---
evaluate.c | 6 ++++++
validation/linear/fn-ptr-deref.c | 22 ++++++++++++++++++++++
2 files changed, 28 insertions(+)
create mode 100644 validation/linear/fn-ptr-deref.c
diff --git a/evaluate.c b/evaluate.c
index b96696d..3859bfc 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -1776,6 +1776,12 @@ static struct symbol *evaluate_dereference(struct expression *expr)
if (ctype->type == SYM_NODE)
ctype = ctype->ctype.base_type;
+ /* Dereferencing a function pointer does nothing. */
+ if (ctype->type == SYM_PTR && ctype->ctype.base_type->type == SYM_FN) {
+ *expr = *op;
+ return expr->ctype;
+ }
+
node = alloc_symbol(expr->pos, SYM_NODE);
target = ctype->ctype.base_type;
diff --git a/validation/linear/fn-ptr-deref.c b/validation/linear/fn-ptr-deref.c
new file mode 100644
index 0000000..9352d1e
--- /dev/null
+++ b/validation/linear/fn-ptr-deref.c
@@ -0,0 +1,22 @@
+void func_a(void);
+static void function_foobar(int n)
+{
+ void (*indir_func_var)(void) = func_a;
+ indir_func_var();
+ (*indir_func_var)();
+}
+/*
+ * check-name: dereference function pointer
+ * check-command: test-linearize $file
+ *
+ * check-output-start
+function_foobar:
+.L0:
+ <entry-point>
+ call func_a
+ call func_a
+ ret
+
+
+ * check-output-end
+ */
--
2.16.1.291.g4437f3f132-goog
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