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:9964
>
> This 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:25755
>
> This 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
>
> > 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:7549
>
> This 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:7534
>
> This 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:7049
>
> This 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:8919
>
> Discarded 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:10002
>
> Discarded by build_x_modify_expr.
>
>
