C PATCH to fix ASAN ICE with a compound literal (PR sanitizer/80659)

[Marek Polacek]

Martin L. asked me to have a look at this ICE with ASAN.  This is an ICE with a
compound literal in a switch.  A hash map gimplify_ctxp->live_switch_vars is
filled when processing DECL_EXPRs with their DECL_EXPR_DECLs.  Such decls should
then be removed from the hash map when gimplifying a BIND_EXPR.

In C, non-static compound literals aren't pushed into any scope, so they were
never found by gimplify_bind_expr, so they stayed in the hash map resulting in
a crash on
 2299       if (gimplify_ctxp->live_switch_vars)
 2300         {
 2301           gcc_assert (gimplify_ctxp->live_switch_vars->elements () == 0);
 2302           delete gimplify_ctxp->live_switch_vars;
 2303         }

We don't add artificial decls to the hash map:
 1647           if (!DECL_ARTIFICIAL (decl) && gimplify_ctxp->live_switch_vars)
 1648             gimplify_ctxp->live_switch_vars->add (decl);

build_compound_literal only marks a decl of a compound literal as artificial
when the compound literal is static.  I think there's no harm in marking
decls of non-static compound literals as artificial, too (provided it's fine to
skip asan instrumentation of compound literals).

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2017-05-16  Marek Polacek  <pola...@redhat.com>

        PR sanitizer/80659
        * c-decl.c (build_compound_literal): Set DECL_ARTIFICIAL even for
        non-static compound literals.

        * gcc.dg/asan/pr80659.c: New test.

diff --git gcc/c/c-decl.c gcc/c/c-decl.c
index b779d37..887e95d 100644
--- gcc/c/c-decl.c
+++ gcc/c/c-decl.c
@@ -5261,6 +5261,7 @@ build_compound_literal (location_t loc, tree type, tree 
init, bool non_const)
   DECL_CONTEXT (decl) = current_function_decl;
   TREE_USED (decl) = 1;
   DECL_READ_P (decl) = 1;
+  DECL_ARTIFICIAL (decl) = 1;
   TREE_TYPE (decl) = type;
   TREE_READONLY (decl) = (TYPE_READONLY (type)
                          || (TREE_CODE (type) == ARRAY_TYPE
@@ -5297,7 +5298,6 @@ build_compound_literal (location_t loc, tree type, tree 
init, bool non_const)
       set_compound_literal_name (decl);
       DECL_DEFER_OUTPUT (decl) = 1;
       DECL_COMDAT (decl) = 1;
-      DECL_ARTIFICIAL (decl) = 1;
       DECL_IGNORED_P (decl) = 1;
       pushdecl (decl);
       rest_of_decl_compilation (decl, 1, 0);
diff --git gcc/testsuite/gcc.dg/asan/pr80659.c 
gcc/testsuite/gcc.dg/asan/pr80659.c
index e69de29..0cbf2e4 100644
--- gcc/testsuite/gcc.dg/asan/pr80659.c
+++ gcc/testsuite/gcc.dg/asan/pr80659.c
@@ -0,0 +1,13 @@
+/* PR sanitizer/80659 */
+/* { dg-do compile } */
+
+void
+foo (int a)
+{
+  switch (a)
+    {
+    case 0:
+      (int[3]) { };
+      int h;
+    }
+}

        Marek