tree-optimization/106868 - bogus -Wdangling-pointer diagnostic
Commit Message
The testcase shows we mishandle the case where there's a pass-through
of a pointer through a function like memcpy. The following adjusts
handling of this copy case to require a taken address and adjust
the PHI case similarly.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/106868
* gimple-ssa-warn-access.cc (pass_waccess::gimple_call_return_arg_ref):
Inline into single user ...
(pass_waccess::check_dangling_uses): ... here and adjust the
call and the PHI case to require that ref.aref is the address
of the decl.
* gcc.dg/Wdangling-pointer-pr106868.c: New testcase.
---
gcc/gimple-ssa-warn-access.cc | 52 ++++++-------------
.../gcc.dg/Wdangling-pointer-pr106868.c | 14 +++++
2 files changed, 30 insertions(+), 36 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/Wdangling-pointer-pr106868.c
@@ -2127,7 +2127,6 @@ private:
/* Return the argument that a call returns. */
tree gimple_call_return_arg (gcall *);
- tree gimple_call_return_arg_ref (gcall *);
/* Check a call for uses of a dangling pointer arguments. */
void check_call_dangling (gcall *);
@@ -4460,24 +4459,6 @@ pass_waccess::gimple_call_return_arg (gcall *call)
return gimple_call_arg (call, argno);
}
-/* Return the decl referenced by the argument that the call STMT to
- a built-in function returns (including with an offset) or null if
- it doesn't. */
-
-tree
-pass_waccess::gimple_call_return_arg_ref (gcall *call)
-{
- if (tree arg = gimple_call_return_arg (call))
- {
- access_ref aref;
- if (m_ptr_qry.get_ref (arg, call, &aref, 0)
- && DECL_P (aref.ref))
- return aref.ref;
- }
-
- return NULL_TREE;
-}
-
/* Check for and diagnose all uses of the dangling pointer VAR to the auto
object DECL whose lifetime has ended. OBJREF is true when VAR denotes
an access to a DECL that may have been clobbered. */
@@ -4646,11 +4627,10 @@ pass_waccess::check_dangling_uses ()
unsigned i;
FOR_EACH_SSA_NAME (i, var, m_func)
{
- /* For each SSA_NAME pointer VAR find the DECL it points to.
- If the DECL is a clobbered local variable, check to see
+ /* For each SSA_NAME pointer VAR find the object it points to.
+ If the object is a clobbered local variable, check to see
if any of VAR's uses (or those of other pointers derived
from VAR) happens after the clobber. If so, warn. */
- tree decl = NULL_TREE;
gimple *def_stmt = SSA_NAME_DEF_STMT (var);
if (is_gimple_assign (def_stmt))
@@ -4660,23 +4640,30 @@ pass_waccess::check_dangling_uses ()
{
if (!POINTER_TYPE_P (TREE_TYPE (var)))
continue;
- decl = TREE_OPERAND (rhs, 0);
+ check_dangling_uses (var, TREE_OPERAND (rhs, 0));
}
else
{
/* For other expressions, check the base DECL to see
if it's been clobbered, most likely as a result of
inlining a reference to it. */
- decl = get_base_address (rhs);
+ tree decl = get_base_address (rhs);
if (DECL_P (decl))
check_dangling_uses (var, decl, false, true);
- continue;
}
}
else if (POINTER_TYPE_P (TREE_TYPE (var)))
{
if (gcall *call = dyn_cast<gcall *>(def_stmt))
- decl = gimple_call_return_arg_ref (call);
+ {
+ if (tree arg = gimple_call_return_arg (call))
+ {
+ access_ref aref;
+ if (m_ptr_qry.get_ref (arg, call, &aref, 0)
+ && aref.deref < 0)
+ check_dangling_uses (var, aref.ref);
+ }
+ }
else if (gphi *phi = dyn_cast <gphi *>(def_stmt))
{
unsigned nargs = gimple_phi_num_args (phi);
@@ -4684,19 +4671,12 @@ pass_waccess::check_dangling_uses ()
{
access_ref aref;
tree arg = gimple_phi_arg_def (phi, i);
- if (!m_ptr_qry.get_ref (arg, phi, &aref, 0)
- || (aref.deref == 0
- && POINTER_TYPE_P (TREE_TYPE (aref.ref))))
- continue;
- check_dangling_uses (var, aref.ref, true);
+ if (m_ptr_qry.get_ref (arg, phi, &aref, 0)
+ && aref.deref < 0)
+ check_dangling_uses (var, aref.ref, true);
}
- continue;
}
- else
- continue;
}
-
- check_dangling_uses (var, decl);
}
}
new file mode 100644
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O -Wdangling-pointer" } */
+
+void alloc(void **p);
+void false_dangling(char **p)
+{
+ {
+ void *q;
+ alloc(&q);
+ *p = q;
+ }
+ char *a = __builtin_memcpy(*p, "", 1);
+ *a = 0; /* { dg-bogus "dangling" } */
+}