The following valid code snippet triggers an ICE since GCC 5.1.0 (it was wrongly rejected in GCC 4.9.4): ===================================== template<typename T> struct A { T x[1]{(__PTRDIFF_TYPE__)this}; }; void foo() { A<A<__PTRDIFF_TYPE__>> a{}; } ===================================== bug.cc: In function 'void foo()': bug.cc:8:28: internal compiler error: in replace_placeholders_r, at cp/tree.c:3148 A<A<__PTRDIFF_TYPE__>> a{}; ^ 0x667871 replace_placeholders_r ../../gcc/gcc/cp/tree.c:3148 0x116564b walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*)) ../../gcc/gcc/tree.c:11387 0x9d03b0 replace_placeholders_r ../../gcc/gcc/cp/tree.c:3188 0x116564b walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*)) ../../gcc/gcc/tree.c:11387 0x9d03b0 replace_placeholders_r ../../gcc/gcc/cp/tree.c:3188 0x116564b walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*)) ../../gcc/gcc/tree.c:11387 0x9d03b0 replace_placeholders_r ../../gcc/gcc/cp/tree.c:3188 0x116564b walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*)) ../../gcc/gcc/tree.c:11387 0x9d03b0 replace_placeholders_r ../../gcc/gcc/cp/tree.c:3188 0x116564b walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*)) ../../gcc/gcc/tree.c:11387 0x9d51d1 replace_placeholders(tree_node*, tree_node*, bool*) ../../gcc/gcc/cp/tree.c:3226 0x9f4bb3 store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc, vl_embed>**, int) ../../gcc/gcc/cp/typeck2.c:851 0x887daa check_initializer ../../gcc/gcc/cp/decl.c:6469 0x89ffdc cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int) ../../gcc/gcc/cp/decl.c:7127 0x93c97b cp_parser_init_declarator ../../gcc/gcc/cp/parser.c:19741 0x943e28 cp_parser_simple_declaration ../../gcc/gcc/cp/parser.c:13059 0x944c38 cp_parser_block_declaration ../../gcc/gcc/cp/parser.c:12884 0x945669 cp_parser_declaration_statement ../../gcc/gcc/cp/parser.c:12478 0x923a73 cp_parser_statement ../../gcc/gcc/cp/parser.c:10927 0x9249e0 cp_parser_statement_seq_opt ../../gcc/gcc/cp/parser.c:11276 Please submit a full bug report, [etc.]
I get ICE already with r185596 when -std=c++1y option has been introduced: pr85148.C:1:29: internal compiler error: tree check: expected tree that contains ‘common’ structure, have ‘constructor’ in perform_member_init, at cp/init.c:661 Then starting with r210653 it is rejected: pr85148.C: In function ‘void foo()’: pr85148.C:8:28: error: could not convert ‘(long int)this’ from ‘long int’ to ‘A<long int>’ A<A<__PTRDIFF_TYPE__>> a{}; ^ pr85148.C: In constructor ‘constexpr A<A<long int> >::A()’: pr85148.C:1:29: error: could not convert ‘(long int)this’ from ‘long int’ to ‘A<long int>’ template<typename T> struct A ^ pr85148.C: In function ‘void foo()’: pr85148.C:8:28: note: synthesized method ‘constexpr A<A<long int> >::A()’ first required here A<A<__PTRDIFF_TYPE__>> a{}; ^ Then starting with r216750 it ICEs in tsubst_copy: pr85148.C: In function ‘void foo()’: pr85148.C:8:28: internal compiler error: in tsubst_copy, at cp/pt.c:12755 A<A<__PTRDIFF_TYPE__>> a{}; ^ 0x71171b tsubst_copy ../../gcc/cp/pt.c:12755 0x720a9b tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool, bool) ../../gcc/cp/pt.c:15464 and finally starting with r234442 in replace_placeholders. It hasn't been fixed by the r258593 changes, seems the PLACEHOLDER_EXPR refers to the outer A when it should be refering to the inner A? Or I'm totally confused on what exactly it should do.
Author: jason Date: Wed Apr 4 16:42:33 2018 New Revision: 259088 URL: https://gcc.gnu.org/viewcvs?rev=259088&root=gcc&view=rev Log: PR c++/85148 - ICE with 'this' in array NSDMI. * tree.c (replace_placeholders_r): Use handled_component_p. Added: trunk/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr11.C Modified: trunk/gcc/cp/ChangeLog trunk/gcc/cp/tree.c
Author: jason Date: Wed Apr 4 16:45:53 2018 New Revision: 259093 URL: https://gcc.gnu.org/viewcvs?rev=259093&root=gcc&view=rev Log: PR c++/85148 - ICE with 'this' in array NSDMI. * tree.c (replace_placeholders_r): Use handled_component_p. Added: branches/gcc-7-branch/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr11.C Modified: branches/gcc-7-branch/gcc/cp/ChangeLog branches/gcc-7-branch/gcc/cp/tree.c
Fixed for 7.4; doesn't seem like a priority for GCC 6.