On 11/16/20 5:45 PM, Patrick Palka wrote:
On Mon, 16 Nov 2020, Jason Merrill wrote:On 11/13/20 10:43 AM, Patrick Palka wrote:On Thu, 12 Nov 2020, Jason Merrill wrote:On 11/12/20 1:27 PM, Patrick Palka wrote:The atom_cache in normalize_atom relies on the assumption that two equivalent (templated) trees (in the sense of cp_tree_equal) must use the same template parameters (according to find_template_parameters). This assumption unfortunately doesn't always hold for TARGET_EXPRs, because cp_tree_equal ignores an artificial target of a TARGET_EXPR, but find_template_parameters walks this target (and its DECL_CONTEXT). Hence two TARGET_EXPRs built by force_target_expr with the same initializer but under different settings of current_function_decl may compare equal according to cp_tree_equal, but find_template_parameters returns a different set of template parameters for them. This breaks the below testcase because during normalization we build two such TARGET_EXPRs (one under current_function_decl=f and another under =g), and then use the same ATOMIC_CONSTR for the two corresponding atoms, leading to a crash during satisfaction of g's associated constraints. This patch works around this assumption violation by removing the source of these templated TARGET_EXPRs. The relevant call to get_target_expr was added in r9-6043, but it seems it's no longer necessary (according to https://gcc.gnu.org/pipermail/gcc-patches/2019-February/517323.html, the call was added in order to avoid regressing on initlist109.C at the time). Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk?OK. I wonder what else asserting !processing_template_decl in build_target_expr would find...FWIW, testing exposed seven distinct paths that trigger such an assert, five of which go through build_cplus_new:Most of these are built as part of overload resolution and then thrown away, only using the result for its type. But I wonder about the build_aggr_init instance.0x6b3983 build_target_expr /gcc/gcc/cp/tree.c:496 0xa94ec8 build_cplus_new(tree_node*, tree_node*, int) /gcc/gcc/cp/tree.c:728 0x91712b force_rvalue(tree_node*, int) /gcc/gcc/cp/cvt.c:569 0x8b8310 build_conditional_expr_1 /gcc/gcc/cp/call.c:5592 0x8ba08c build_conditional_expr(op_location_t const&, tree_node*, tree_node*, tree_node*, int) /gcc/gcc/cp/call.c:5777 0xaa70fb build_x_conditional_expr(unsigned int, tree_node*, tree_node*, tree_node*, int) /gcc/gcc/cp/typeck.c:7133 0x9cc9fa cp_parser_assignment_expression /gcc/gcc/cp/parser.c:9964This one gets discarded by build_x_conditional_expr.0x6b3983 build_target_expr /gcc/gcc/cp/tree.c:496 0xa94ec8 build_cplus_new(tree_node*, tree_node*, int) /gcc/gcc/cp/tree.c:728 0x97d185 expand_default_init /gcc/gcc/cp/init.c:1924 0x97d185 expand_aggr_init_1 /gcc/gcc/cp/init.c:2101 0x97f026 build_aggr_init(tree_node*, tree_node*, int, int) /gcc/gcc/cp/init.c:1835 0x92c88d build_aggr_init_full_exprs /gcc/gcc/cp/decl.c:6696 0x92c88d check_initializer /gcc/gcc/cp/decl.c:6857 0x950982 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int) /gcc/gcc/cp/decl.c:7699 0x960c7e grokfield(cp_declarator const*, cp_decl_specifier_seq*, tree_node*, bool, tree_node*, tree_node*) /gcc/gcc/cp/decl2.c:1000 0xa02ceb cp_parser_member_declaration /gcc/gcc/cp/parser.c:25755This one looks dubious. Which testcase?IIRC many constexpr testcases trigger this one, for instance g++.dg/cpp0x/constexpr-initlist9.C and g++.dg/cpp0x/constexpr-static6.C: gcc/testsuite/g++.dg/cpp0x/constexpr-initlist9.C: In function ‘void generate_sudoku(T)’: gcc/testsuite/g++.dg/cpp0x/constexpr-initlist9.C:34:50: internal compiler error: in build_target_expr, at cp/tree.c:495 34 | constexpr auto positions = make_grid_positions(); // fail | ^ 0x6b3c47 build_target_expr /home/patrick/code/gcc/gcc/cp/tree.c:495 0xa97248 build_cplus_new(tree_node*, tree_node*, int) /home/patrick/code/gcc/gcc/cp/tree.c:727 0x97eed5 expand_default_init /home/patrick/code/gcc/gcc/cp/init.c:1924 0x97eed5 expand_aggr_init_1 /home/patrick/code/gcc/gcc/cp/init.c:2101 0x980d76 build_aggr_init(tree_node*, tree_node*, int, int) /home/patrick/code/gcc/gcc/cp/init.c:1835 0x92e5cd build_aggr_init_full_exprs /home/patrick/code/gcc/gcc/cp/decl.c:6696 0x92e5cd check_initializer /home/patrick/code/gcc/gcc/cp/decl.c:6857 0x9525c2 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int) /home/patrick/code/gcc/gcc/cp/decl.c:7699 0x9fcdf7 cp_parser_init_declarator /home/patrick/code/gcc/gcc/cp/parser.c:21362 gcc/testsuite/g++.dg/cpp0x/constexpr-static6.C:17:28: internal compiler error: in build_target_expr, at cp/tree.c:495 17 | constexpr static B t = B(); | ^ 0x6b3c47 build_target_expr /home/patrick/code/gcc/gcc/cp/tree.c:495 0xa97248 build_cplus_new(tree_node*, tree_node*, int) /home/patrick/code/gcc/gcc/cp/tree.c:727 0x97eed5 expand_default_init /home/patrick/code/gcc/gcc/cp/init.c:1924 0x97eed5 expand_aggr_init_1 /home/patrick/code/gcc/gcc/cp/init.c:2101 0x980d76 build_aggr_init(tree_node*, tree_node*, int, int) /home/patrick/code/gcc/gcc/cp/init.c:1835 0x92e5cd build_aggr_init_full_exprs /home/patrick/code/gcc/gcc/cp/decl.c:6696 0x92e5cd check_initializer /home/patrick/code/gcc/gcc/cp/decl.c:6857 0x9525c2 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int) /home/patrick/code/gcc/gcc/cp/decl.c:7699 0x9629ce grokfield(cp_declarator const*, cp_decl_specifier_seq*, tree_node*, bool, tree_node*, tree_node*) /home/patrick/code/gcc/gcc/cp/decl2.c:1000
Thanks. This is part of trying to produce a real value for a non-dependent constexpr variable; the TARGET_EXPR gets melted down before long, so it's OK.
0x6b3983 build_target_expr /gcc/gcc/cp/tree.c:496 0xa94ee8 build_cplus_new(tree_node*, tree_node*, int) /gcc/gcc/cp/tree.c:728 0x8a0ed5 build_cxx_call(tree_node*, int, tree_node**, int, tree_node*) /gcc/gcc/cp/call.c:9747 0xabed0b cp_build_function_call_vec(tree_node*, vec<tree_node*, va_gc, vl_embed>**, int, tree_node*) /gcc/gcc/cp/typeck.c:4025 0xa75a30 finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool, bool, int) /gcc/gcc/cp/semantics.c:2728 0x9e9383 cp_parser_postfix_expression /gcc/gcc/cp/parser.c:7549This is discarded by finish_call_expr.0x6b3983 build_target_expr /gcc/gcc/cp/tree.c:496 0xa94ee8 build_cplus_new(tree_node*, tree_node*, int) /gcc/gcc/cp/tree.c:728 0x8a0ed5 build_cxx_call(tree_node*, int, tree_node**, int, tree_node*) /gcc/gcc/cp/call.c:9747 0xabed0b cp_build_function_call_vec(tree_node*, vec<tree_node*, va_gc, vl_embed>**, int, tree_node*) /gcc/gcc/cp/typeck.c:4025 0x95eb40 build_offset_ref_call_from_tree(tree_node*, vec<tree_node*, va_gc, vl_embed>**, int) /gcc/gcc/cp/decl2.c:5292 0x9e9b1f cp_parser_postfix_expression /gcc/gcc/cp/parser.c:7534This is discarded by build_offset_ref_call_from_tree.0x6b3983 build_target_expr /gcc/gcc/cp/tree.c:496 0xa94ec8 build_cplus_new(tree_node*, tree_node*, int) /gcc/gcc/cp/tree.c:728 0x8b67c2 perform_direct_initialization_if_possible(tree_node*, tree_node*, bool, int) /gcc/gcc/cp/call.c:12038 0xaba6a9 build_static_cast_1 /gcc/gcc/cp/typeck.c:7607 0xabb500 build_static_cast(unsigned int, tree_node*, tree_node*, int) /gcc/gcc/cp/typeck.c:7813 0x9e9f9e cp_parser_postfix_expression /gcc/gcc/cp/parser.c:7049This is discarded by build_static_cast.0x6b3983 build_target_expr /gcc/gcc/cp/tree.c:496 0x97fb53 build_new_1 /gcc/gcc/cp/init.c:3281 0x982382 build_new(unsigned int, vec<tree_node*, va_gc, vl_embed>**, tree_node*, tree_node*, vec<tree_node*, va_gc, vl_embed>**, int, int) /gcc/gcc/cp/init.c:3817 0x9f2107 cp_parser_new_expression /gcc/gcc/cp/parser.c:8919Discarded by build_new.0x6b3983 build_target_expr /gcc/gcc/cp/tree.c:496 0xaa2b0f get_target_expr(tree_node*) /gcc/gcc/cp/tree.c:899 0xaa2b0f stabilize_expr(tree_node*, tree_node**) /gcc/gcc/cp/tree.c:5509 0xabfa2a cp_build_modify_expr(unsigned int, tree_node*, tree_code, tree_node*, int) /gcc/gcc/cp/typeck.c:8736 0x8b7c91 build_new_op_1 /gcc/gcc/cp/call.c:6537 0x8b809d build_new_op(op_location_t const&, tree_code, int, tree_node*, tree_node*, tree_node*, tree_node**, int) /gcc/gcc/cp/call.c:6623 0xac0b04 build_x_modify_expr(unsigned int, tree_node*, tree_code, tree_node*, int) /gcc/gcc/cp/typeck.c:8936 0x9ccafe cp_parser_assignment_expression /gcc/gcc/cp/parser.c:10002Discarded by build_x_modify_expr.
