analyzer: remove -Wanalyzer-use-of-uninitialized-value for GCC 10

From what I can tell -Wanalyzer-use-of-uninitialized-value has not
yet found a true diagnostic in real-world code, and seems to be
particularly susceptible to false positives.  These relate to bugs in
the region_model code.

For GCC 10 it seems best to remove this warning, which this patch does.
Internally it also removes POISON_KIND_UNINIT.

I'm working on a rewrite of the region_model code for GCC 11 that I
hope will fix these issues, and allow this warning to be reintroduced.

gcc/analyzer/ChangeLog:
	PR analyzer/94447
	PR analyzer/94639
	PR analyzer/94732
	PR analyzer/94754
	* analyzer.opt (Wanalyzer-use-of-uninitialized-value): Delete.
	* program-state.cc (selftest::test_program_state_dumping): Update
	expected dump result for removal of "uninit".
	* region-model.cc (poison_kind_to_str): Delete POISON_KIND_UNINIT
	case.
	(root_region::ensure_stack_region): Initialize stack with null
	svalue_id rather than with a typeless POISON_KIND_UNINIT value.
	(root_region::ensure_heap_region): Likewise for the heap.
	(region_model::dump_summary_of_rep_path_vars): Remove
	summarization of uninit values.
	(region_model::validate): Remove check that the stack has a
	POISON_KIND_UNINIT value.
	(poisoned_value_diagnostic::emit): Remove POISON_KIND_UNINIT
	case.
	(poisoned_value_diagnostic::describe_final_event): Likewise.
	(selftest::test_dump): Update expected dump result for removal of
	"uninit".
	(selftest::test_svalue_equality): Remove "uninit" and "freed".
	* region-model.h (enum poison_kind): Remove POISON_KIND_UNINIT.

gcc/ChangeLog:
	PR analyzer/94447
	PR analyzer/94639
	PR analyzer/94732
	PR analyzer/94754
	* doc/invoke.texi (Static Analyzer Options): Remove
	-Wanalyzer-use-of-uninitialized-value.
	(-Wno-analyzer-use-of-uninitialized-value): Remove item.

gcc/testsuite/ChangeLog:
	PR analyzer/94447
	PR analyzer/94639
	PR analyzer/94732
	PR analyzer/94754
	* gcc.dg/analyzer/data-model-1.c: Mark "use of uninitialized
	value" warnings as xfail for now.
	* gcc.dg/analyzer/data-model-5b.c: Remove uninitialized warning.
	* gcc.dg/analyzer/pr94099.c: Mark "uninitialized" warning as xfail
	for now.
	* gcc.dg/analyzer/pr94447.c: New test.
	* gcc.dg/analyzer/pr94639.c: New test.
	* gcc.dg/analyzer/pr94732.c: New test.
	* gcc.dg/analyzer/pr94754.c: New test.
	* gcc.dg/analyzer/zlib-6.c: Mark "uninitialized" warning as xfail
	for now.

16 files changed, 129 insertions, 99 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e7a4edb..dc64c76 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2020-04-28  David Malcolm  <dmalcolm@redhat.com>
+
+	PR analyzer/94447
+	PR analyzer/94639
+	PR analyzer/94732
+	PR analyzer/94754
+	* doc/invoke.texi (Static Analyzer Options): Remove
+	-Wanalyzer-use-of-uninitialized-value.
+	(-Wno-analyzer-use-of-uninitialized-value): Remove item.
+
 2020-04-28  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/94809
diff --git a/gcc/analyzer/ChangeLog b/gcc/analyzer/ChangeLog
index 3f136f4..3c8f458 100644
--- a/gcc/analyzer/ChangeLog
+++ b/gcc/analyzer/ChangeLog
@@ -1,3 +1,29 @@
+2020-04-28  David Malcolm  <dmalcolm@redhat.com>
+
+	PR analyzer/94447
+	PR analyzer/94639
+	PR analyzer/94732
+	PR analyzer/94754
+	* analyzer.opt (Wanalyzer-use-of-uninitialized-value): Delete.
+	* program-state.cc (selftest::test_program_state_dumping): Update
+	expected dump result for removal of "uninit".
+	* region-model.cc (poison_kind_to_str): Delete POISON_KIND_UNINIT
+	case.
+	(root_region::ensure_stack_region): Initialize stack with null
+	svalue_id rather than with a typeless POISON_KIND_UNINIT value.
+	(root_region::ensure_heap_region): Likewise for the heap.
+	(region_model::dump_summary_of_rep_path_vars): Remove
+	summarization of uninit values.
+	(region_model::validate): Remove check that the stack has a
+	POISON_KIND_UNINIT value.
+	(poisoned_value_diagnostic::emit): Remove POISON_KIND_UNINIT
+	case.
+	(poisoned_value_diagnostic::describe_final_event): Likewise.
+	(selftest::test_dump): Update expected dump result for removal of
+	"uninit".
+	(selftest::test_svalue_equality): Remove "uninit" and "freed".
+	* region-model.h (enum poison_kind): Remove POISON_KIND_UNINIT.
+
 2020-04-01  David Malcolm  <dmalcolm@redhat.com>
 
 	PR analyzer/94378
diff --git a/gcc/analyzer/analyzer.opt b/gcc/analyzer/analyzer.opt
index 22cf4b0..3133cdd 100644
--- a/gcc/analyzer/analyzer.opt
+++ b/gcc/analyzer/analyzer.opt
@@ -98,10 +98,6 @@ Wanalyzer-use-of-pointer-in-stale-stack-frame
 Common Var(warn_analyzer_use_of_pointer_in_stale_stack_frame) Init(1) Warning
 Warn about code paths in which a pointer to a stale stack frame is used.
 
-Wanalyzer-use-of-uninitialized-value
-Common Var(warn_analyzer_use_of_uninitialized_value) Init(1) Warning
-Warn about code paths in which an uninitialized value is used.
-
 Wanalyzer-too-complex
 Common Var(warn_analyzer_too_complex) Init(0) Warning
 Warn if the code is too complicated for the analyzer to fully explore.
diff --git a/gcc/analyzer/program-state.cc b/gcc/analyzer/program-state.cc
index 43396c6..1a5843b 100644
--- a/gcc/analyzer/program-state.cc
+++ b/gcc/analyzer/program-state.cc
@@ -1449,23 +1449,21 @@ test_program_state_dumping ()
   ASSERT_DUMP_EQ
     (s, ext_state, false,
      "rmodel: r0: {kind: `root', parent: null, sval: null}\n"
-     "|-heap: r1: {kind: `heap', parent: r0, sval: sv0}\n"
-     "|  |: sval: sv0: {poisoned: uninit}\n"
+     "|-heap: r1: {kind: `heap', parent: r0, sval: null}\n"
      "|  `-r2: {kind: `symbolic', parent: r1, sval: null, possibly_null: true}\n"
      "`-globals: r3: {kind: `globals', parent: r0, sval: null, map: {`p': r4}}\n"
-     "  `-`p': r4: {kind: `primitive', parent: r3, sval: sv1, type: `void *'}\n"
-     "    |: sval: sv1: {type: `void *', &r2}\n"
+     "  `-`p': r4: {kind: `primitive', parent: r3, sval: sv0, type: `void *'}\n"
+     "    |: sval: sv0: {type: `void *', &r2}\n"
      "    |: type: `void *'\n"
      "svalues:\n"
-     "  sv0: {poisoned: uninit}\n"
-     "  sv1: {type: `void *', &r2}\n"
+     "  sv0: {type: `void *', &r2}\n"
      "constraint manager:\n"
      "  equiv classes:\n"
      "  constraints:\n"
-     "malloc: {sv1: unchecked (`p')}\n");
+     "malloc: {sv0: unchecked (`p')}\n");
 
   ASSERT_DUMP_EQ (s, ext_state, true,
-		  "rmodel: p: &r2 malloc: {sv1: unchecked (`p')}");
+		  "rmodel: p: &r2 malloc: {sv0: unchecked (`p')}");
 }
 
 /* Verify that program_state::dump_to_pp works for string literals.  */
diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
index 30fe72b..22049a3 100644
--- a/gcc/analyzer/region-model.cc
+++ b/gcc/analyzer/region-model.cc
@@ -788,8 +788,6 @@ poison_kind_to_str (enum poison_kind kind)
     {
     default:
       gcc_unreachable ();
-    case POISON_KIND_UNINIT:
-      return "uninit";
     case POISON_KIND_FREED:
       return "freed";
     case POISON_KIND_POPPED_STACK:
@@ -3204,12 +3202,9 @@ root_region::ensure_stack_region (region_model *model)
 {
   if (m_stack_rid.null_p ())
     {
-      svalue_id uninit_sid
-	= model->add_svalue (new poisoned_svalue (POISON_KIND_UNINIT,
-						  NULL_TREE));
       m_stack_rid
 	= model->add_region (new stack_region (model->get_root_rid (),
-					       uninit_sid));
+					       svalue_id::null ()));
     }
   return m_stack_rid;
 }
@@ -3270,12 +3265,9 @@ root_region::ensure_heap_region (region_model *model)
 {
   if (m_heap_rid.null_p ())
     {
-      svalue_id uninit_sid
-	= model->add_svalue (new poisoned_svalue (POISON_KIND_UNINIT,
-						  NULL_TREE));
       m_heap_rid
 	= model->add_region (new heap_region (model->get_root_rid (),
-					      uninit_sid));
+					      svalue_id::null ()));
     }
   return m_heap_rid;
 }
@@ -3859,7 +3851,6 @@ region_model::dump_summary_of_rep_path_vars (pretty_printer *pp,
   unsigned i;
   path_var *pv;
   auto_vec<tree> unknown_trees;
-  auto_vec<tree> uninit_trees;
   FOR_EACH_VEC_ELT (*rep_path_vars, i, pv)
     {
       if (TREE_CODE (pv->m_tree) == STRING_CST)
@@ -3908,14 +3899,9 @@ region_model::dump_summary_of_rep_path_vars (pretty_printer *pp,
 	  {
 	    poisoned_svalue *poisoned_sval = as_a <poisoned_svalue *> (sval);
 	    enum poison_kind pkind = poisoned_sval->get_poison_kind ();
-	    if (pkind == POISON_KIND_UNINIT)
-	      uninit_trees.safe_push (pv->m_tree);
-	    else
-	      {
-		dump_separator (pp, is_first);
-		dump_tree (pp, pv->m_tree);
-		pp_printf (pp, ": %s", poison_kind_to_str (pkind));
-	      }
+	    dump_separator (pp, is_first);
+	    dump_tree (pp, pv->m_tree);
+	    pp_printf (pp, ": %s", poison_kind_to_str (pkind));
 	  }
 	  break;
 	case SK_SETJMP:
@@ -3928,7 +3914,6 @@ region_model::dump_summary_of_rep_path_vars (pretty_printer *pp,
 
   /* Print unknown and uninitialized values in consolidated form.  */
   dump_vec_of_tree (pp, is_first, unknown_trees, "unknown");
-  dump_vec_of_tree (pp, is_first, uninit_trees, "uninit");
 }
 
 /* Assert that this object is valid.  */
@@ -3949,18 +3934,6 @@ region_model::validate () const
     r->validate (*this);
 
   // TODO: anything else?
-
-  /* Verify that the stack region (if any) has an "uninitialized" value.  */
-  region *stack_region = get_root_region ()->get_stack_region (this);
-  if (stack_region)
-    {
-      svalue_id stack_value_sid = stack_region->get_value_direct ();
-      svalue *stack_value = get_svalue (stack_value_sid);
-      gcc_assert (stack_value->get_kind () == SK_POISONED);
-      poisoned_svalue *subclass = stack_value->dyn_cast_poisoned_svalue ();
-      gcc_assert (subclass);
-      gcc_assert (subclass->get_poison_kind () == POISON_KIND_UNINIT);
-    }
 }
 
 /* Global data for use by svalue_id_cmp_by_constant_svalue.  */
@@ -4087,16 +4060,6 @@ public:
       {
       default:
 	gcc_unreachable ();
-      case POISON_KIND_UNINIT:
-	{
-	  diagnostic_metadata m;
-	  m.add_cwe (457); /* "CWE-457: Use of Uninitialized Variable".  */
-	  return warning_meta (rich_loc, m,
-			       OPT_Wanalyzer_use_of_uninitialized_value,
-			       "use of uninitialized value %qE",
-			       m_expr);
-	}
-	break;
       case POISON_KIND_FREED:
 	{
 	  diagnostic_metadata m;
@@ -4125,9 +4088,6 @@ public:
       {
       default:
 	gcc_unreachable ();
-      case POISON_KIND_UNINIT:
-	return ev.formatted_print ("use of uninitialized value %qE here",
-				   m_expr);
       case POISON_KIND_FREED:
 	return ev.formatted_print ("use after %<free%> of %qE here",
 				   m_expr);
@@ -7578,14 +7538,10 @@ test_dump ()
 
   ASSERT_DUMP_EQ (model, false,
 		  "r0: {kind: `root', parent: null, sval: null}\n"
-		  "|-stack: r1: {kind: `stack', parent: r0, sval: sv0}\n"
-		  "|  |: sval: sv0: {poisoned: uninit}\n"
+		  "|-stack: r1: {kind: `stack', parent: r0, sval: null}\n"
 		  "|-globals: r2: {kind: `globals', parent: r0, sval: null, map: {}}\n"
-		  "`-heap: r3: {kind: `heap', parent: r0, sval: sv1}\n"
-		  "  |: sval: sv1: {poisoned: uninit}\n"
+		  "`-heap: r3: {kind: `heap', parent: r0, sval: null}\n"
 		  "svalues:\n"
-		  "  sv0: {poisoned: uninit}\n"
-		  "  sv1: {poisoned: uninit}\n"
 		  "constraint manager:\n"
 		  "  equiv classes:\n"
 		  "  constraints:\n");
@@ -7798,15 +7754,6 @@ test_svalue_equality ()
   ASSERT_NE (cst_int_42->hash (), cst_int_0->hash ());
   ASSERT_NE (*cst_int_42, *cst_int_0);
 
-  svalue *uninit = new poisoned_svalue (POISON_KIND_UNINIT, NULL_TREE);
-  svalue *freed = new poisoned_svalue (POISON_KIND_FREED, NULL_TREE);
-
-  ASSERT_EQ (uninit->hash (), uninit->hash ());
-  ASSERT_EQ (*uninit, *uninit);
-
-  ASSERT_NE (uninit->hash (), freed->hash ());
-  ASSERT_NE (*uninit, *freed);
-
   svalue *unknown_0 = new unknown_svalue (ptr_type_node);
   svalue *unknown_1 = new unknown_svalue (ptr_type_node);
   ASSERT_EQ (unknown_0->hash (), unknown_0->hash ());
@@ -7815,24 +7762,16 @@ test_svalue_equality ()
 
   /* Comparisons between different kinds of svalue.  */
   ASSERT_NE (*ptr_to_r0, *cst_int_42);
-  ASSERT_NE (*ptr_to_r0, *uninit);
   ASSERT_NE (*ptr_to_r0, *unknown_0);
   ASSERT_NE (*cst_int_42, *ptr_to_r0);
-  ASSERT_NE (*cst_int_42, *uninit);
   ASSERT_NE (*cst_int_42, *unknown_0);
-  ASSERT_NE (*uninit, *ptr_to_r0);
-  ASSERT_NE (*uninit, *cst_int_42);
-  ASSERT_NE (*uninit, *unknown_0);
   ASSERT_NE (*unknown_0, *ptr_to_r0);
   ASSERT_NE (*unknown_0, *cst_int_42);
-  ASSERT_NE (*unknown_0, *uninit);
 
   delete ptr_to_r0;
   delete ptr_to_r1;
   delete cst_int_42;
   delete cst_int_0;
-  delete uninit;
-  delete freed;
   delete unknown_0;
   delete unknown_1;
 }
diff --git a/gcc/analyzer/region-model.h b/gcc/analyzer/region-model.h
index 2c9ee39..ad3dd1d 100644
--- a/gcc/analyzer/region-model.h
+++ b/gcc/analyzer/region-model.h
@@ -684,9 +684,6 @@ public:
 
 enum poison_kind
 {
-  /* For use to describe uninitialized memory.  */
-  POISON_KIND_UNINIT,
-
   /* For use to describe freed memory.  */
   POISON_KIND_FREED,
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index a101928..04b84e3 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -8256,7 +8256,6 @@ Enabling this option effectively enables the following warnings:
 -Wanalyzer-tainted-array-index @gol
 -Wanalyzer-unsafe-call-within-signal-handler @gol
 -Wanalyzer-use-after-free @gol
--Wanalyzer-use-of-uninitialized-value @gol
 -Wanalyzer-use-of-pointer-in-stale-stack-frame @gol
 }
 
@@ -8429,15 +8428,6 @@ to disable it.
 This diagnostic warns for paths through the code in which a pointer
 is dereferenced that points to a variable in a stale stack frame.
 
-@item -Wno-analyzer-use-of-uninitialized-value
-@opindex Wanalyzer-use-of-uninitialized-value
-@opindex Wno-analyzer-use-of-uninitialized-value
-This warning requires @option{-fanalyzer}, which enables it; use
-@option{-Wno-analyzer-use-of-uninitialized-value} to disable it.
-
-This diagnostic warns for paths through the code in which an uninitialized
-value is used.
-
 @end table
 
 Pertinent parameters for controlling the exploration are:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e94c09c..a1ee87e 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,21 @@
+2020-04-28  David Malcolm  <dmalcolm@redhat.com>
+
+	PR analyzer/94447
+	PR analyzer/94639
+	PR analyzer/94732
+	PR analyzer/94754
+	* gcc.dg/analyzer/data-model-1.c: Mark "use of uninitialized
+	value" warnings as xfail for now.
+	* gcc.dg/analyzer/data-model-5b.c: Remove uninitialized warning.
+	* gcc.dg/analyzer/pr94099.c: Mark "uninitialized" warning as xfail
+	for now.
+	* gcc.dg/analyzer/pr94447.c: New test.
+	* gcc.dg/analyzer/pr94639.c: New test.
+	* gcc.dg/analyzer/pr94732.c: New test.
+	* gcc.dg/analyzer/pr94754.c: New test.
+	* gcc.dg/analyzer/zlib-6.c: Mark "uninitialized" warning as xfail
+	for now.
+
 2020-04-28  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/94809
diff --git a/gcc/testsuite/gcc.dg/analyzer/data-model-1.c b/gcc/testsuite/gcc.dg/analyzer/data-model-1.c
index e2bd1f9..1db9913 100644
--- a/gcc/testsuite/gcc.dg/analyzer/data-model-1.c
+++ b/gcc/testsuite/gcc.dg/analyzer/data-model-1.c
@@ -849,7 +849,7 @@ void test_36 (int i)
 int test_37 (void)
 {
   int *ptr;
-  return *ptr; /* { dg-warning "use of uninitialized value 'ptr'" } */
+  return *ptr; /* { dg-warning "use of uninitialized value 'ptr'" "uninit-warning-removed" { xfail *-*-* } } */
 }
 
 /* Write through uninitialized pointer.  */
@@ -857,7 +857,7 @@ int test_37 (void)
 void test_37a (int i)
 {
   int *ptr;
-  *ptr = i; /* { dg-warning "use of uninitialized value 'ptr'" } */
+  *ptr = i; /* { dg-warning "use of uninitialized value 'ptr'" "uninit-warning-removed" { xfail *-*-* } } */
 }
 
 // TODO: the various other ptr deref poisonings
diff --git a/gcc/testsuite/gcc.dg/analyzer/data-model-5b.c b/gcc/testsuite/gcc.dg/analyzer/data-model-5b.c
index 11b5671..76e351d 100644
--- a/gcc/testsuite/gcc.dg/analyzer/data-model-5b.c
+++ b/gcc/testsuite/gcc.dg/analyzer/data-model-5b.c
@@ -76,8 +76,7 @@ void unref (string_obj *obj)
   if (--obj->str_base.ob_refcnt == 0)
     {
       //__analyzer_dump();
-      obj->str_base.ob_type->tp_dealloc ((base_obj *)obj); /* { dg-bogus "use of uninitialized value '<unknown>'" "" { xfail *-*-* } } */
-      // TODO (xfail): not sure what's going on here
+      obj->str_base.ob_type->tp_dealloc ((base_obj *)obj);
     }
 }
 
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr94099.c b/gcc/testsuite/gcc.dg/analyzer/pr94099.c
index 0a34f56..a116c49 100644
--- a/gcc/testsuite/gcc.dg/analyzer/pr94099.c
+++ b/gcc/testsuite/gcc.dg/analyzer/pr94099.c
@@ -21,7 +21,7 @@ pl (void)
   for (sc = 0; sc < 1; ++sc)
     {
       th.gk.hk = 0;
-      th.gk.bg[sc] = 0; /* { dg-warning "uninitialized" } */
+      th.gk.bg[sc] = 0; /* { dg-warning "uninitialized" "uninit-warning-removed" { xfail *-*-* } } */
       l3 (&th);
     }
 }
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr94447.c b/gcc/testsuite/gcc.dg/analyzer/pr94447.c
new file mode 100644
index 0000000..1aecebb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr94447.c
@@ -0,0 +1,10 @@
+struct foo
+{
+  int *v;
+};
+
+int test (void)
+{
+  struct foo f = {};
+  return *f.v;
+}
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr94639.c b/gcc/testsuite/gcc.dg/analyzer/pr94639.c
new file mode 100644
index 0000000..2dbb57e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr94639.c
@@ -0,0 +1,14 @@
+#include <string.h>
+
+void validatedatetime(const char *str)
+{
+  const char *templates[] = {"dddd-dd-dd dd:dd", "dddd-dd-dd"};
+
+  size_t len = strlen(str);
+
+  for (unsigned t = 0; t < 2; t++) {
+    if (len != strlen(templates[t])) {
+      continue;
+    }
+  }
+}
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr94732.c b/gcc/testsuite/gcc.dg/analyzer/pr94732.c
new file mode 100644
index 0000000..1aa154f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr94732.c
@@ -0,0 +1,13 @@
+typedef struct { int *a; } S;
+int *f (void);
+static void g (S *x)
+{
+  int *p = x->a;
+  p[0] = 0;
+}
+void h (void)
+{
+  S x[1];
+  x->a = f ();
+  g (x);
+}
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr94754.c b/gcc/testsuite/gcc.dg/analyzer/pr94754.c
new file mode 100644
index 0000000..3fae20c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr94754.c
@@ -0,0 +1,20 @@
+[[gnu::nonnull]]
+static
+void init_x(int cond, int **x, int *y)
+{
+  if (!cond)
+    return;
+  *x = y;
+}
+
+int foo(int cond)
+{
+  int *x;
+  int y = 7;
+
+  if (cond < 2)
+    return -1;
+  init_x(cond, &x, &y);
+
+  return *x;
+}
diff --git a/gcc/testsuite/gcc.dg/analyzer/zlib-6.c b/gcc/testsuite/gcc.dg/analyzer/zlib-6.c
index d68c387..0d814c0 100644
--- a/gcc/testsuite/gcc.dg/analyzer/zlib-6.c
+++ b/gcc/testsuite/gcc.dg/analyzer/zlib-6.c
@@ -41,7 +41,7 @@ int inflate_blocks(inflate_blocks_statef *s, z_stream *z, int r) {
         return inflate_flush(s, z, r);
       }
     };
-    b |= ((uLong)(n--, *p++)) << k; /* { dg-warning "use of uninitialized value" } */
+    b |= ((uLong)(n--, *p++)) << k; /* { dg-warning "use of uninitialized value" "uninit-warning-removed" { xfail *-*-* } } */
     k += 8;
   }
 }