re PR c++/83996 (ICE with zero-sized array)

	PR c++/83996
	* constexpr.c (cxx_fold_indirect_ref): Compute ((foo *)&fooarray)[1]
	=> fooarray[1] in offset_int.

	* g++.dg/ext/pr83996.C: New test.

From-SVN: r257160

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 90e8ff18203284ec04f94cf0843a86944b0a591b..e8b0e1e140aa1a77a7d14027615b62495101a1fa 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2018-01-29  Marek Polacek  <polacek@redhat.com>
+
+       PR c++/83996
+       * constexpr.c (cxx_fold_indirect_ref): Compute ((foo *)&fooarray)[1]
+       => fooarray[1] in offset_int.
+
 2018-01-29  Jason Merrill  <jason@redhat.com>
 
        PR c++/83942 - wrong unused warning with static_cast.

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 4d2ee4a28fca6a6e0a7851725a0a4d9f5dde7214..0a1944f6dad4e01ada48d8da29bb8cd1c47833bd 100644 (file)
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -3143,11 +3143,17 @@ cxx_fold_indirect_ref (location_t loc, tree type, tree op0, bool *empty_base)
              tree min_val = size_zero_node;
              if (type_domain && TYPE_MIN_VALUE (type_domain))
                min_val = TYPE_MIN_VALUE (type_domain);
-             op01 = size_binop_loc (loc, EXACT_DIV_EXPR, op01,
-                                    TYPE_SIZE_UNIT (type));
-             op01 = size_binop_loc (loc, PLUS_EXPR, op01, min_val);
-             return build4_loc (loc, ARRAY_REF, type, op00, op01,
-                                NULL_TREE, NULL_TREE);
+             offset_int off = wi::to_offset (op01);
+             offset_int el_sz = wi::to_offset (TYPE_SIZE_UNIT (type));
+             offset_int remainder;
+             off = wi::divmod_trunc (off, el_sz, SIGNED, &remainder);
+             if (remainder == 0 && TREE_CODE (min_val) == INTEGER_CST)
+               {
+                 off = off + wi::to_offset (min_val);
+                 op01 = wide_int_to_tree (sizetype, off);
+                 return build4_loc (loc, ARRAY_REF, type, op00, op01,
+                                    NULL_TREE, NULL_TREE);
+               }
            }
          /* Also handle conversion to an empty base class, which
             is represented with a NOP_EXPR.  */

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3713a81227cea5ef13cea48ba69927bdc2932a02..a74854b3e1291bd28eebf549e2f50a7d9bd448f2 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -3,6 +3,9 @@
        PR c/83966
        * gcc.dg/format/Wsuggest-attribute-1.c: New test.
 
+       PR c++/83996
+       * g++.dg/ext/pr83996.C: New test.
+
 2018-01-29  Richard Biener  <rguenther@suse.de>
 
        PR tree-optimization/84057

diff --git a/gcc/testsuite/g++.dg/ext/pr83996.C b/gcc/testsuite/g++.dg/ext/pr83996.C
new file mode 100644 (file)
index 0000000..e663d72
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/pr83996.C
@@ -0,0 +1,11 @@
+// PR c++/83996
+// { dg-do compile }
+// { dg-options "" }
+
+int z[] = { };
+
+int
+main (void)
+{
+  __builtin_printf ("%d\n", *(z + 1));
+}