c++: Fix value-init crash in template [PR93676]

Since <https://gcc.gnu.org/ml/gcc-patches/2015-02/msg00556.html> we
attempt to value-initialize in build_vec_init even when there's no
initializer but the type has a constexpr default constructor.  But
build_value_init doesn't work in templates, and build_vec_init
creates a lot of garbage that would not be used anyway, so don't
call it in a template.

	PR c++/93676 - value-init crash in template.
	* init.c (build_new_1): Don't call build_vec_init in a template.

	* g++.dg/cpp0x/nsdmi-template19.C: New test.

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 5ba298fe5e93a79bb851518f23836324d8c9e250..d34730c6ec10c28db25334ffc87252828261aa95 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2020-02-26  Marek Polacek  <polacek@redhat.com>
+
+       PR c++/93676 - value-init crash in template.
+       * init.c (build_new_1): Don't call build_vec_init in a template.
+
 2020-02-26  Marek Polacek  <polacek@redhat.com>
 
        PR c++/93862 - ICE with static_cast when converting from int[].

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index d480660445e8ee66c814ec6ff32af50b6aca4d51..61ed3aa7e93ef5cbc6bc6c87d3ae2c047ccde751 100644 (file)
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3511,13 +3511,17 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
          explicit_value_init_p = true;
        }
 
-      if (processing_template_decl && explicit_value_init_p)
+      if (processing_template_decl)
        {
+         /* Avoid an ICE when converting to a base in build_simple_base_path.
+            We'll throw this all away anyway, and build_new will create
+            a NEW_EXPR.  */
+         tree t = fold_convert (build_pointer_type (elt_type), data_addr);
          /* build_value_init doesn't work in templates, and we don't need
             the initializer anyway since we're going to throw it away and
             rebuild it at instantiation time, so just build up a single
             constructor call to get any appropriate diagnostics.  */
-         init_expr = cp_build_fold_indirect_ref (data_addr);
+         init_expr = cp_build_fold_indirect_ref (t);
          if (type_build_ctor_call (elt_type))
            init_expr = build_special_member_call (init_expr,
                                                   complete_ctor_identifier,

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 08146db0cedefd0d914fcf436e583ac4aa9827ab..572989b2c7a00ab166a0e2137a72249672bd222f 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-02-26  Marek Polacek  <polacek@redhat.com>
+
+       PR c++/93676 - value-init crash in template.
+       * g++.dg/cpp0x/nsdmi-template19.C: New test.
+
 2020-02-26  Marek Polacek  <polacek@redhat.com>
 
        PR c++/93862 - ICE with static_cast when converting from int[].

diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
new file mode 100644 (file)
index 0000000..f3e2cb8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template19.C
@@ -0,0 +1,13 @@
+// PR c++/93676 - value-init crash in template.
+// { dg-do compile { target c++11 } }
+
+struct P {
+  int x = 0;
+};
+
+template<class T>
+struct S {
+  S() { new P[2][2]; }
+};
+
+S<int> s;