PR analyzer/105264 reports that the analyzer can fail to treat
(PTR + IDX) and PTR[IDX] as referring to the same memory under
some situations.
There are various ways in which this can happen when IDX is a
symbolic value, due to having several ways in which such memory
regions can be referred to symbolically. I attempted to fix this by
being smarter when folding svalues and regions, but this fix
seems too fiddly to attempt in stage 4.
Instead, this less ambitious patch fixes a false positive from
-Wanalyzer-use-of-uninitialized-value by making the analyzer's escape
analysis smarter, so that it treats *PTR as escaping when
(PTR + OFFSET) is passed to an external function, and thus
it treats *PTR as possibly-initialized (the "passing &PTR[IDX]" case
was already working).
Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
Pushed to trunk as r12-8169-ga358e4b60815b4.
gcc/analyzer/ChangeLog:
PR analyzer/105264
* region-model-reachability.cc (reachable_regions::handle_parm):
Use maybe_get_deref_base_region rather than just region_svalue, to
handle pointer arithmetic also.
* svalue.cc (svalue::maybe_get_deref_base_region): New.
* svalue.h (svalue::maybe_get_deref_base_region): New decl.
gcc/testsuite/ChangeLog:
PR analyzer/105264
* gcc.dg/analyzer/torture/symbolic-10.c: New test.
Signed-off-by: David Malcolm <dmalc...@redhat.com>
---
gcc/analyzer/region-model-reachability.cc | 8 +---
gcc/analyzer/svalue.cc | 42 +++++++++++++++++++
gcc/analyzer/svalue.h | 2 +
.../gcc.dg/analyzer/torture/symbolic-10.c | 40 ++++++++++++++++++
4 files changed, 86 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/analyzer/torture/symbolic-10.c
diff --git a/gcc/analyzer/region-model-reachability.cc
b/gcc/analyzer/region-model-reachability.cc
index b876b8f0363..12d09c3e500 100644
--- a/gcc/analyzer/region-model-reachability.cc
+++ b/gcc/analyzer/region-model-reachability.cc
@@ -252,12 +252,8 @@ reachable_regions::handle_parm (const svalue *sval, tree
param_type)
m_mutable_svals.add (sval);
else
m_reachable_svals.add (sval);
- if (const region_svalue *parm_ptr
- = sval->dyn_cast_region_svalue ())
- {
- const region *pointee_reg = parm_ptr->get_pointee ();
- add (pointee_reg, is_mutable);
- }
+ if (const region *base_reg = sval->maybe_get_deref_base_region ())
+ add (base_reg, is_mutable);
/* Treat all svalues within a compound_svalue as reachable. */
if (const compound_svalue *compound_sval
= sval->dyn_cast_compound_svalue ())
diff --git a/gcc/analyzer/svalue.cc b/gcc/analyzer/svalue.cc
index 536bc288dbf..a1403f0fbef 100644
--- a/gcc/analyzer/svalue.cc
+++ b/gcc/analyzer/svalue.cc
@@ -651,6 +651,48 @@ svalue::all_zeroes_p () const
return false;
}
+/* If this svalue is a pointer, attempt to determine the base region it points
+ to. Return NULL on any problems. */
+
+const region *
+svalue::maybe_get_deref_base_region () const
+{
+ const svalue *iter = this;
+ while (1)
+ {
+ switch (iter->get_kind ())
+ {
+ default:
+ return NULL;
+
+ case SK_REGION:
+ {
+ const region_svalue *region_sval
+ = as_a <const region_svalue *> (iter);
+ return region_sval->get_pointee ()->get_base_region ();
+ }
+
+ case SK_BINOP:
+ {
+ const binop_svalue *binop_sval
+ = as_a <const binop_svalue *> (iter);
+ switch (binop_sval->get_op ())
+ {
+ case POINTER_PLUS_EXPR:
+ /* If we have a symbolic value expressing pointer arithmetic,
+ use the LHS. */
+ iter = binop_sval->get_arg0 ();
+ continue;
+
+ default:
+ return NULL;
+ }
+ return NULL;
+ }
+ }
+ }
+}
+
/* class region_svalue : public svalue. */
/* Implementation of svalue::dump_to_pp vfunc for region_svalue. */
diff --git a/gcc/analyzer/svalue.h b/gcc/analyzer/svalue.h
index 4bbe8588b8d..29ea2ee6408 100644
--- a/gcc/analyzer/svalue.h
+++ b/gcc/analyzer/svalue.h
@@ -175,6 +175,8 @@ public:
per-type and thus it's meaningless for them to "have state". */
virtual bool can_have_associated_state_p () const { return true; }
+ const region *maybe_get_deref_base_region () const;
+
protected:
svalue (complexity c, tree type)
: m_complexity (c), m_type (type)
diff --git a/gcc/testsuite/gcc.dg/analyzer/torture/symbolic-10.c
b/gcc/testsuite/gcc.dg/analyzer/torture/symbolic-10.c
new file mode 100644
index 00000000000..b2f3a8a1d86
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/torture/symbolic-10.c
@@ -0,0 +1,40 @@
+/* Verify that -fanalyzer considers that mmfs escapes when passing either:
+ *(mmfs + i)
+ and
+ (&mmfs[i])
+ to an external function (for symbolic i). */
+
+typedef struct s_mmfile {
+ char *ptr;
+ long size;
+} mmfile_t;
+
+void init_mmfile(mmfile_t *ptr);
+
+long test__init_via_ptr_arith__read_via_array_idx(int i)
+{
+ mmfile_t mmfs[3];
+ init_mmfile(mmfs + i);
+ return mmfs[i].size; /* { dg-bogus "uninit" } */
+}
+
+long test__init_via_array_idx__read_via_ptr_arith(int i)
+{
+ mmfile_t mmfs[3];
+ init_mmfile(&mmfs[i]);
+ return (mmfs + i)->size; /* { dg-bogus "uninit" } */
+}
+
+long test__ptr_arith_for_both(int i)
+{
+ mmfile_t mmfs[3];
+ init_mmfile(mmfs + i);
+ return (mmfs + i)->size; /* { dg-bogus "uninit" } */
+}
+
+long test__array_idx_for_both(int i)
+{
+ mmfile_t mmfs[3];
+ init_mmfile(&mmfs[i]);
+ return mmfs[i].size; /* { dg-bogus "uninit" } */
+}
--
2.26.3
