https://gcc.gnu.org/g:ed026106ce420c7d9dd4d89caac017b6f235e219
commit r13-8756-ged026106ce420c7d9dd4d89caac017b6f235e219
Author: David Malcolm <dmalc...@redhat.com>
Date: Thu May 9 13:09:31 2024 -0400
analyzer: fix -Wanalyzer-deref-before-check false positive seen in loop
header macro [PR109251]
Backported from commit r14-9586-g9093f275e0a343 (moving tests from
c-c++-common to gcc.dg)
gcc/analyzer/ChangeLog:
PR analyzer/109251
* sm-malloc.cc (deref_before_check::emit): Reject cases where the
check is in a loop header within a macro expansion.
(deref_before_check::loop_header_p): New.
gcc/testsuite/ChangeLog:
PR analyzer/109251
* gcc.dg/analyzer/deref-before-check-pr109251-1.c: New test.
* gcc.dg/analyzer/deref-before-check-pr109251-2.c: New test.
Signed-off-by: David Malcolm <dmalc...@redhat.com>
Diff:
---
gcc/analyzer/sm-malloc.cc | 30 +++++++++++
.../analyzer/deref-before-check-pr109251-1.c | 60 ++++++++++++++++++++++
.../analyzer/deref-before-check-pr109251-2.c | 37 +++++++++++++
3 files changed, 127 insertions(+)
diff --git a/gcc/analyzer/sm-malloc.cc b/gcc/analyzer/sm-malloc.cc
index 64295cfb66e7..e9384a14dead 100644
--- a/gcc/analyzer/sm-malloc.cc
+++ b/gcc/analyzer/sm-malloc.cc
@@ -1565,6 +1565,21 @@ public:
if (linemap_location_from_macro_definition_p (line_table, check_loc))
return false;
+ /* Reject warning if the check is in a loop header within a
+ macro expansion. This rejects cases like:
+ | deref of x;
+ | [...snip...]
+ | FOR_EACH(x) {
+ | [...snip...]
+ | }
+ where the FOR_EACH macro tests for non-nullness of x, since
+ the user is hoping to encapsulate the details of iteration
+ in the macro, and the extra check on the first iteration
+ would just be noise if we reported it. */
+ if (loop_header_p (m_check_enode->get_point ())
+ && linemap_location_from_macro_expansion_p (line_table, check_loc))
+ return false;
+
/* Reject if m_deref_expr is sufficiently different from m_arg
for cases where the dereference is spelled differently from
the check, which is probably two different ways to get the
@@ -1621,6 +1636,21 @@ public:
}
private:
+ static bool loop_header_p (const program_point &point)
+ {
+ const supernode *snode = point.get_supernode ();
+ if (!snode)
+ return false;
+ for (auto &in_edge : snode->m_preds)
+ {
+ if (const cfg_superedge *cfg_in_edge
+ = in_edge->dyn_cast_cfg_superedge ())
+ if (cfg_in_edge->back_edge_p ())
+ return true;
+ }
+ return false;
+ }
+
static bool sufficiently_similar_p (tree expr_a, tree expr_b)
{
pretty_printer *pp_a = global_dc->printer->clone ();
diff --git a/gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr109251-1.c
b/gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr109251-1.c
new file mode 100644
index 000000000000..769cffae6d74
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr109251-1.c
@@ -0,0 +1,60 @@
+/* Reduced from linux-5.10.162's kernel/sched/fair.c,
+ with !CONFIG_FAIR_GROUP_SCHED. */
+
+#define NULL ((void*)0)
+
+struct load_weight
+{
+ unsigned long weight;
+ /* [...snip...] */
+};
+
+struct sched_entity
+{
+ struct load_weight load;
+ /* [...snip...] */
+ unsigned int on_rq;
+ /* [...snip...] */
+};
+
+struct cfs_rq
+{
+ /* [...snip...] */
+ unsigned int nr_running;
+ /* [...snip...] */
+};
+
+extern int
+__calc_delta(int delta_exec, unsigned long weight /* [...snip...] */);
+
+/* !CONFIG_FAIR_GROUP_SCHED */
+#define for_each_sched_entity(se) \
+ for (; se; se = (struct sched_entity *)NULL)
+
+extern struct cfs_rq*
+cfs_rq_of(struct sched_entity* se);
+
+extern int
+__sched_period(unsigned long nr_running);
+
+int
+sched_slice(struct cfs_rq* cfs_rq, struct sched_entity* se)
+{
+ unsigned int nr_running = cfs_rq->nr_running;
+ int slice;
+
+ /* [...snip...] */
+
+ slice = __sched_period(nr_running + !se->on_rq);
+
+ for_each_sched_entity(se) {
+ /* [...snip...] */
+ cfs_rq = cfs_rq_of(se);
+ /* [...snip...] */
+ slice = __calc_delta(slice, se->load.weight);
+ }
+
+ /* [...snip...] */
+
+ return slice;
+}
diff --git a/gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr109251-2.c
b/gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr109251-2.c
new file mode 100644
index 000000000000..8e85a47d315e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr109251-2.c
@@ -0,0 +1,37 @@
+struct node
+{
+ struct node *next;
+ int val;
+};
+
+int test_loop_1 (struct node *n)
+{
+ int total = 0;
+ if (n->val = 42)
+ return -1;
+ for (struct node *iter = n; iter; iter=iter->next)
+ total += iter->val;
+ return total;
+}
+
+int test_loop_2 (struct node *n)
+{
+ int total = 0;
+ if (n->val = 42)
+ return -1;
+ for (; n; n=n->next)
+ total += n->val;
+ return total;
+}
+
+#define FOR_EACH_NODE(ITER) for (; (ITER); (ITER)=(ITER)->next)
+
+int test_loop_3 (struct node *n)
+{
+ int total = 0;
+ if (n->val = 42)
+ return -1;
+ FOR_EACH_NODE (n)
+ total += n->val;
+ return total;
+}
