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[C++ PATCH] Fix constexpr.c find_array_ctor_elt (PR c++/84808)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Jason Merrill <jason at redhat dot com>, Nathan Sidwell <nathan at acm dot org>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Mon, 12 Mar 2018 21:58:25 +0100
- Subject: [C++ PATCH] Fix constexpr.c find_array_ctor_elt (PR c++/84808)
- Authentication-results: sourceware.org; auth=none
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
The following testcase ICEs, because in code to break up a RANGE_EXPR
we have a reference to a constructor element:
constructor_elt &elt = (*elts)[middle];
and do conditionally:
vec_safe_insert (CONSTRUCTOR_ELTS (ary), middle, e);
and later:
e.value = unshare_constructor (elt.value);
vec_safe_insert can reallocate the array whose element elt references,
and so &elt.value then points to uninitialized memory.
Fixed by remembering elt.value before we adjust the CONSTRUCTOR_ELTS.
Additionally, I've found that in the ctor where normally all indexes were
sizetype ones suddenly some of them had integer_type_node type, the
dindex = fold_convert (sizetype, dindex);
line ought to fix that. The rest is just formatting fix.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2018-03-12 Jakub Jelinek <jakub@redhat.com>
PR c++/84808
* constexpr.c (find_array_ctor_elt): Don't use elt reference after
first potential CONSTRUCTOR_ELTS reallocation. Convert dindex to
sizetype. Formatting fixes.
* g++.dg/cpp1y/constexpr-84808.C: New test.
--- gcc/cp/constexpr.c.jj 2018-03-07 22:52:02.000000000 +0100
+++ gcc/cp/constexpr.c 2018-03-12 12:39:46.890321137 +0100
@@ -2194,9 +2194,9 @@ find_array_ctor_elt (tree ary, tree dind
that the same is true of the other elements and index directly. */
if (end > 0)
{
- tree cindex = (*elts)[end-1].index;
+ tree cindex = (*elts)[end - 1].index;
if (TREE_CODE (cindex) == INTEGER_CST
- && compare_tree_int (cindex, end-1) == 0)
+ && compare_tree_int (cindex, end - 1) == 0)
{
if (i < end)
return i;
@@ -2225,6 +2225,8 @@ find_array_ctor_elt (tree ary, tree dind
constructor_elt e;
tree lo = TREE_OPERAND (idx, 0);
tree hi = TREE_OPERAND (idx, 1);
+ tree value = elt.value;
+ dindex = fold_convert (sizetype, dindex);
if (tree_int_cst_lt (lo, dindex))
{
/* There are still some lower elts; shorten the range. */
@@ -2238,7 +2240,7 @@ find_array_ctor_elt (tree ary, tree dind
/* Append the element we want to insert. */
++middle;
e.index = dindex;
- e.value = unshare_constructor (elt.value);
+ e.value = unshare_constructor (value);
vec_safe_insert (CONSTRUCTOR_ELTS (ary), middle, e);
}
else
@@ -2254,8 +2256,8 @@ find_array_ctor_elt (tree ary, tree dind
e.index = hi;
else
e.index = build2 (RANGE_EXPR, sizetype, new_lo, hi);
- e.value = unshare_constructor (elt.value);
- vec_safe_insert (CONSTRUCTOR_ELTS (ary), middle+1, e);
+ e.value = unshare_constructor (value);
+ vec_safe_insert (CONSTRUCTOR_ELTS (ary), middle + 1, e);
}
}
return middle;
--- gcc/testsuite/g++.dg/cpp1y/constexpr-84808.C.jj 2018-03-12 12:45:29.472374837 +0100
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-84808.C 2018-03-12 12:46:11.742381465 +0100
@@ -0,0 +1,27 @@
+// PR c++/84808
+// { dg-do compile { target c++14 } }
+
+struct A { int i; constexpr A () : i() {} };
+struct B { A a[24]; };
+
+constexpr int
+foo (int n)
+{
+ B b;
+ ++b.a[n + 20].i;
+ ++b.a[n + 18].i;
+ ++b.a[n + 16].i;
+ ++b.a[n + 14].i;
+ ++b.a[n + 12].i;
+ ++b.a[n + 10].i;
+ ++b.a[n + 8].i;
+ ++b.a[n + 6].i;
+ ++b.a[n + 4].i;
+ ++b.a[n + 2].i;
+ ++b.a[n].i;
+ return b.a[2].i + b.a[4].i + b.a[6].i + b.a[8].i + b.a[10].i
+ + b.a[12].i + b.a[14].i + b.a[16].i + b.a[18].i + b.a[20].i + b.a[22].i;
+}
+
+constexpr int i = foo (2);
+static_assert (i == 11, "");
Jakub