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2020-04-17c++: Non-type-dependent variadic lambda init-capture [PR94483]Patrick Palka2-1/+8
In this PR, we're ICEing on a use of an 'int... a' template parameter pack as part of the variadic lambda init-capture [...z=a]. The unexpected thing about this variadic init-capture is that it is not type-dependent, and so the call to do_auto_deduction from lambda_capture_field_type actually resolves its type to 'int' instead of exiting early like it does for a type-dependent variadic initializer. This later confuses add_capture which, according to one of its comments, assumes that 'type' is always 'auto' for a variadic init-capture. The simplest fix (and the approach that this patch takes) seems to be to avoid doing auto deduction in lambda_capture_field_type when the initializer uses parameter packs, so that we always return 'auto' even in the non-type-dependent case. gcc/cp/ChangeLog: PR c++/94483 * lambda.c (lambda_capture_field_type): Avoid doing auto deduction if the explicit initializer has parameter packs. gcc/testsuite/ChangeLog: PR c++/94483 * g++.dg/cpp2a/lambda-pack-init5.C: New test.
2020-04-17c++: Hard error with tentative parse of declaration [PR88754]Patrick Palka2-0/+10
In the testcase for this PR, we try to parse the statement A(value<0>()); first tentatively as a declaration (with a parenthesized declarator), and during this tentative parse we end up issuing a hard error from cp_parser_check_template_parameters about its invalidness as a declaration. Rather than issuing a hard error, it seems we should instead simulate an error since we're parsing tentatively. This would then allow cp_parser_statement to recover and successfully parse the statement as an expression-statement instead. gcc/cp/ChangeLog: PR c++/88754 * parser.c (cp_parser_check_template_parameters): Before issuing a hard error, first try simulating an error instead. gcc/testsuite/ChangeLog: PR c++/88754 * g++.dg/parse/ambig10.C: New test.
2020-04-17c, c++: Fix two redundantAssignment warnings [PR94629]Jakub Jelinek2-1/+7
This change fixes two obvious redundant assignments reported by cppcheck: trunk.git/gcc/c/c-parser.c:16969:2: style: Variable 'data.clauses' is reassigned a value before the old one has been used. [redundantAssignment] trunk.git/gcc/cp/call.c:5116:9: style: Variable 'arg2' is reassigned a value before the old one has been used. [redundantAssignment] 2020-04-17 Jakub Jelinek <jakub@redhat.com> PR other/94629 * c-parser.c (c_parser_oacc_routine): Remove redundant assignment to data.clauses. * call.c (build_conditional_expr_1): Remove redundant assignment to arg2.
2020-04-16coroutines: Back out mandate for tail-calls at O < 2 [PR94359]Iain Sandoe1-14/+2
For symmetric transfers to work with C++20 coroutines, it is currently necessary to tail call the callee coroutine from resume method of the caller coroutine. However there are several targets which don't support an indirect tail call to an arbitrary callee. Unfortunately, the target 'function_ok_for_sibcall' is not usable from the front end in all cases. While it is possible to add a new hook to cover this circumstance, it is too late in the release cycle to be sure of getting the setting correct for all targets. So, this patch backs out the use of function_ok_for_sibcall () and the mandate of CALL_EXPR_MUST_TAIL_CALL from the symmetric transfer. Targets that can make indirect tail calls to arbitrary callees will still be able to make use of the symmetric transfer (without risking overrunning the stack) for optimization levels >= 2. The draft standard does not mandate unlimited symmetric transfers, so removing this is a QOI issue (albeit an important one) rather than a correctness one. The test is moved and adjusted so that it can be opted into by any target that supports the necessary tailcall. gcc/cp/ChangeLog: 2020-04-16 Iain Sandoe <iain@sandoe.co.uk> PR c++/94359 * coroutines.cc (build_actor_fn): Back out use of targetm.function_ok_for_sibcall. Do not mark the resume call as CALL_EXPR_MUST_TAIL_CALL. gcc/testsuite/ChangeLog: 2020-04-16 Iain Sandoe <iain@sandoe.co.uk> PR c++/94359 * g++.dg/coroutines/torture/symmetric-transfer-00-basic.C: Move.. * g++.dg/coroutines/symmetric-transfer-00-basic.C: ..here and adjust to run at O2 for targets supporting the necessary tail call.
2020-04-16c++: Error recovery with erroneous DECL_INITIAL [PR94475]Patrick Palka2-1/+9
Here we're ICE'ing in do_narrow during error-recovery, because ocp_convert returns error_mark_node after it attempts to reduce a const decl to its erroneous DECL_INITIAL via scalar_constant_value, and we later pass this error_mark_node to fold_build2 which isn't prepared to handle error_mark_nodes. We could fix this ICE in do_narrow by checking if ocp_convert returns error_mark_node, but for the sake of consistency and for better error recovery it seems it'd be preferable if ocp_convert didn't care that a const decl's initializer is erroneous and would instead proceed as if the decl was not const, which is the approach that this patch takes. gcc/cp/ChangeLog: PR c++/94475 * cvt.c (ocp_convert): If the result of scalar_constant_value is erroneous, ignore it and use the original expression. gcc/testsuite/ChangeLog: PR c++/94475 * g++.dg/conversion/err-recover2.C: New test. * g++.dg/diagnostic/pr84138.C: Remove now-bogus warning. * g++.dg/warn/Wsign-compare-8.C: Remove now-bogus warning.
2020-04-16c++: Fix pasto in structured binding diagnostics [PR94571]Jakub Jelinek2-6/+12
This snippet has been copied from the non-structured binding declaration parsing later in the function, and while for non-structured bindings it can be followed by comma or semicolon, structured bindings may be only followed by semicolon. Or, do we want to have a different message for the case when there is a comma (and keep this corrected one only if there is something else) that would explain better what is the bug (or add a fix-it hint)? Marek said in the PR that clang++ reports error: decomposition declaration must be the only declaration in its group There is another thing Marek noted (though, something for different spot), that diagnostic for auto x(1), [e,f] = test2; could also use a clearer wording like the above (or a fix-it hint), but the question is if we should assume [ after , as a structured binding or if we should do some tentative parsing first to figure out if it looks like a structured binding. 2020-04-16 Jakub Jelinek <jakub@redhat.com> PR c++/94571 * parser.c (cp_parser_simple_declaration): Fix up a pasto in diagnostics. * g++.dg/cpp1z/decomp51.C: New test.
2020-04-15openmp: Reject requires directives not at file or namespace scope [PR94593]Jakub Jelinek2-0/+13
This change started with a bugreport about a typo in one requires testcase (diagnosed with -Wunknown-pragmas only), but following discussion lead to noting that we do not diagnose restriction that requires directives in C/C++ may only appear at file or namespace scope; and several our tests violated that. 2020-04-15 Jakub Jelinek <jakub@redhat.com> PR c/94593 * c-parser.c (c_parser_pragma) <case PRAGMA_OMP_REQUIRES>: Reject requires directive when not at file scope. * parser.c (cp_parser_pragma) <case PRAGMA_OMP_REQUIRES>: Reject requires directive when not at file or namespace scope. * c-c++-common/gomp/requires-1.c: Fix a typo, requries -> requires. Move directives to file scope. (i): Remove. * c-c++-common/gomp/requires-2.c: Move directives to file scope. (i, foo): Remove. * c-c++-common/gomp/requires-4.c: Move directives to file scope. * c-c++-common/gomp/atomic-19.c: Move requires directive to file scope. * c-c++-common/gomp/atomic-20.c: Likewise. * c-c++-common/gomp/atomic-21.c: Likewise. * c-c++-common/gomp/atomic-22.c: Likewise. * gcc.dg/gomp/requires-1.c: New test. * g++.dg/gomp/requires-1.C: New test. * g++.dg/gomp/requires-2.C: New test. * g++.dg/gomp/atomic-18.C: Move requires directive to file scope.
2020-04-14coroutines: Fix compile error with symmetric transfers [PR94359]Iain Sandoe2-7/+21
For symmetric transfers to work with C++20 coroutines, it is currently necessary to tail call the callee coroutine from resume method of the caller coroutine. The current codegen marks these resume calls as "MUST_TAIL_CALL" to indicate that the tail call is required for correctness. Unfortunately, several targets have ABI constraints that prevent an indirect tail-call, which results in the PRs compile error. The change here tests the target sibcall hook for the resume expression and only marks it as requiring a tail call if that's supported. This doesn't fix the underlying problem; that really a solution is needed to allow the tail-calls (or equivalent) to take place - but that will be deferred until next stage 1. gcc/cp/ChangeLog: 2020-04-14 Iain Sandoe <iain@sandoe.co.uk> PR c++/94359 * coroutines.cc (build_actor_fn): Check that the target can support the resume tailcall before mandating it. gcc/testsuite/ChangeLog: 2020-04-14 Iain Sandoe <iain@sandoe.co.uk> PR c++/94359 * g++.dg/coroutines/torture/symmetric-transfer-00-basic.C: Expect a run fail for targets without arbitrary indirect tail-calls.
2020-04-14c++: "'decltype_type' not supported" in diagnostic [PR85278]Patrick Palka2-7/+17
This fixes a garbled concepts diagnostic by moving the handling of DECLTYPE_TYPE from pp_cxx_type_specifier_seq to cxx_pretty_printer::simple_type_specifier, a move which also seems to be more consistent with the language grammar. This patch also fixes pretty printing of rvalue reference types via cxx_pretty_printer::type_id, which eventually calls pp_c_pointer which currently doesn't distinguish between lvalue and rvalue references. gcc/c-family/ChangeLog: PR c++/85278 * c-pretty-print.c (pp_c_pointer) <case REFERENCE_TYPE>: Print a double ampersand if it's an rvalue reference type. gcc/cp/ChangeLog: PR c++/85278 * cxx-pretty-print.c (cxx_pretty_printer:simple_type_specifier) <case DECLTYPE_TYPE>: Handle DECLTYPE_TYPE here instead of ... (pp_cxx_type_specifier_seq) <case DECLTYPE_TYPE>: ... here. (cxx_pretty_printer::direct_abstract_declarator) <case DECLTYPE_TYPE>: New no-op case. gcc/testsuite/ChangeLog: PR c++/85278 * g++.dg/concepts/diagnostic9.C: New test.
2020-04-14c++: Stray RESULT_DECLs in result of constexpr call [PR94034]Patrick Palka3-0/+67
When evaluating the initializer of 'a' in the following example struct A { A() = default; A(const A&); A *p = this; }; constexpr A foo() { return {}; } constexpr A a = foo(); the PLACEHOLDER_EXPR for 'this' in the aggregate initializer returned by foo gets resolved to the RESULT_DECL of foo. But due to guaranteed RVO, the 'this' should really be resolved to '&a'. Fixing this properly by immediately resolving 'this' and PLACEHOLDER_EXPRs to the ultimate object under construction would in general mean that we would no longer be able to cache constexpr calls for which RVO possibly applies, because the result of the call may now depend on the ultimate object under construction. So as a mostly correct stopgap solution that retains cachability of RVO'd constexpr calls, this patch fixes this issue by rewriting all occurrences of the RESULT_DECL in the result of a constexpr function call with the current object under construction, after the call returns. This means the 'this' pointer during construction of the temporary will still point to the temporary object instead of the ultimate object, but besides that this approach seems functionally equivalent to the proper approach. gcc/cp/ChangeLog: PR c++/94034 * constexpr.c (replace_result_decl_data): New struct. (replace_result_decl_data_r): New function. (replace_result_decl): New function. (cxx_eval_call_expression): Use it. * tree.c (build_aggr_init_expr): Set the location of the AGGR_INIT_EXPR to that of its initializer. gcc/testsuite/ChangeLog: PR c++/94034 * g++.dg/cpp0x/constexpr-empty15.C: New test. * g++.dg/cpp1y/constexpr-nsdmi6a.C: New test. * g++.dg/cpp1y/constexpr-nsdmi6b.C: New test. * g++.dg/cpp1y/constexpr-nsdmi7a.C: New test. * g++.dg/cpp1y/constexpr-nsdmi7b.C: New test.
2020-04-13c++: Improve redeclared parameter name diagnostic [PR94588]Marek Polacek2-3/+11
While reviewing [basic.scope.param] I noticed we don't show the location of the previous declaration when giving an error about "A parameter name shall not be redeclared in the outermost block of the function definition". PR c++/94588 * name-lookup.c (check_local_shadow): Add an inform call. * g++.dg/diagnostic/redeclaration-1.C: Add dg-message.
2020-04-13c++: Infinite diagnostic loop with decltype([]{}) [PR94521]Patrick Palka2-0/+7
We are hitting a recursive loop when printing the signature of a function containing a decltype([]{}) type. The loop is dump_function_decl -> dump_substitution -> dump_template_bindings -> dump_type -> dump_aggr_type -> dump_scope -> dump_function_decl and we loop because dump_template_bindings wants to print the resolved type of decltype([]{}) (i.e. just a lambda type), so it calls dump_aggr_type, which wants to print the function scope of the lambda type. But the function scope of the lambda type is the function which we're in the middle of printing. This patch breaks the loop by passing TFF_NO_FUNCTION_ARGUMENTS to dump_function_decl from dump_scope, so that we avoid recursing into dump_substitution and ultimately looping. This also means we no longer emit the "[with ...]" clause when printing a function template scope, and we instead just emit its template argument list in a more natural way, e.g. instead of foo(int, char) [with T=bool]::x we would now print foo<bool>::x which seems like an improvement on its own. The full signature of the function 'spam' in the below testcase is now void spam(decltype (<lambda>)*) [with T = int; decltype (<lambda>) = spam<int>::<lambda()>] gcc/cp/ChangeLog: PR c++/94521 * error.c (dump_scope): Pass TFF_NO_FUNCTION_ARGUMENTS to dump_function_decl when printing a function template instantiation as a scope. gcc/testsuite/ChangeLog: PR c++/94521 * g++.dg/cpp2a/lambda-uneval12.C: New test.
2020-04-13c++: More self-modifying constexpr init [PR94470]Patrick Palka2-12/+16
In this PR we're incorrectly rejecting a self-modifying constexpr initializer as a consequence of the fix for PR78572. It looks like however that the fix for PR78572 is obsoleted by the fix for PR89336: the testcase from the former PR successfully compiles even with its fix reverted. But then further testing showed that the analogous testcase of PR78572 where the array has an aggregate element type is still problematic (i.e. we ICE) even with the fix for PR78572 applied. The reason is that in cxx_eval_bare_aggregate we attach a constructor_elt of aggregate type always to the end of the new CONSTRUCTOR, but that's not necessarily correct if the CONSTRUCTOR is self-modifying. We should instead be using get_or_insert_ctor_field to insert the constructor_elt in the right place. So this patch reverts the PR78572 fix and makes the appropriate changes to cxx_eval_bare_aggregate. This fixes PR94470, and we now are also able to fully reduce the initializers of 'arr' and 'arr2' in the new test array57.C to constant initializers. gcc/cp/ChangeLog: PR c++/94470 * constexpr.c (get_or_insert_ctor_field): Set default value of parameter 'pos_hint' to -1. (cxx_eval_bare_aggregate): Use get_or_insert_ctor_field instead of assuming the the next index belongs at the end of the new CONSTRUCTOR. (cxx_eval_store_expression): Revert PR c++/78572 fix. gcc/testsuite/ChangeLog: PR c++/94470 * g++.dg/cpp1y/constexpr-nsdmi8.C: New test. * g++.dg/cpp1y/constexpr-nsdmi9.C: New test. * g++.dg/init/array57.C: New test.
2020-04-13c++: lambdas with internal linkage are different to no-linkage [PR94426]Nathan Sidwell4-14/+37
My fix for 94147 was confusing no-linkage with internal linkage, at the language level. That's wrong. (the std is confusing here, because it describes linkage of names (which is wrong), and lambdas have no names) Lambdas with extra-scope, have linkage. However, at the implementation-level that linkage is at least as restricted as the linkage of the extra-scope decl. Further, when instantiating a variable initialized by a lambda, we must determine the visibility of the variable itself, before instantiating its initializer. If the template arguments are internal (or no-linkage), the variable will have internal linkage, regardless of the linkage of the template it is instantiated from. We need to know that before instantiating the lambda, so we can restrict its linkage correctly. * decl2.c (determine_visibility): A lambda's visibility is affected by its extra scope. * pt.c (instantiate_decl): Determine var's visibility before instantiating its initializer. * tree.c (no_linkage_check): Revert code looking at visibility of lambda's extra scope. ` gcc/cp/ * g++.dg/cpp0x/lambda/pr94426-[12].C: New. * g++.dg/abi/lambda-vis.C: Drop a warning. * g++.dg/cpp0x/lambda/lambda-mangle.C: Lambda visibility on variable changes. * g++.dg/opt/dump1.C: Drop warnings of no import.
2020-04-11Correct PR numbers in the last Changelog.Iain Sandoe1-1/+1
I mistyped the PR number in the actual fix commit r10-7682-g0666767eb4cc864f00ba34d97b9d58f8dc650bba.
2020-04-11coroutines: Revise await expansions [PR94528]Iain Sandoe2-208/+263
The expansions for await expressions were specific to particular cases, this revises it to be more generic. a: Revise co_await statement walkers. We want to process the co_awaits one statement at a time. We also want to be able to determine the insertion points for new bind scopes needed to cater for temporaries that are captured by reference and have lifetimes that need extension to the end of the full expression. Likewise, the handling of captured references in the evaluation of conditions might result in the need to make a frame copy. This reorganises the statement walking code to make it easier to extend for these purposes. b: Factor reference-captured temp code. We want to be able to use the code that writes a new bind expr with vars (and their initializers) from several places, so split that out of the maybe_promote_captured_temps() function into a new replace_statement_captures (). Update some comments. c: Generalize await statement expansion. This revises the expansion to avoid the need to expand conditionally on the tree type. It resolves PR 94528. gcc/cp/ChangeLog: 2020-04-10 Iain Sandoe <iain@sandoe.co.uk> PR c++/94538 * coroutines.cc (co_await_expander): Remove. (expand_one_await_expression): New. (process_one_statement): New. (await_statement_expander): New. (build_actor_fn): Revise to use per-statement expander. (struct susp_frame_data): Reorder and comment. (register_awaits): Factor code. (replace_statement_captures): New, factored from... (maybe_promote_captured_temps):.. here. (await_statement_walker): Revise to process per statement. (morph_fn_to_coro): Use revised susp_frame_data layout. gcc/testsuite/ChangeLog: 2020-04-10 Iain Sandoe <iain@sandoe.co.uk> PR c++/94538 * g++.dg/coroutines/pr94528.C: New test.
2020-04-10c++: make __is_constructible work with paren-init of aggrs [PR94149]Marek Polacek2-3/+46
In C++20 this is well-formed: using T = int[2]; T t(1, 2); which means that std::is_constructible_v<int[2], int, int> should be true. But constructible_expr immediately returned the error_mark_node when it saw a list with more than one element. To give accurate results in C++20, we have to try initializing the aggregate from a parenthesized list of values. To not repeat the same mistake as in c++/93790, if there's only one element, I'm trying {} only when () didn't succeed. is_constructible5.C verifies this. In paren-init24.C std::is_nothrow_constructible_v doesn't work due to error: invalid 'static_cast' from type 'int' to type 'int [1]' and error: functional cast to array type 'int [2]' This needs to be fixed in libstdc++. PR c++/94149 * method.c (constructible_expr): In C++20, try using parenthesized initialization of aggregates to determine the result of __is_constructible. * g++.dg/cpp2a/paren-init24.C: New test. * g++.dg/cpp2a/paren-init25.C: New test. * g++.dg/ext/is_constructible5.C: New test.
2020-04-10Simplify co_await_expander.Bin Cheng2-22/+7
gcc/cp 2020-04-10 Bin Cheng <bin.cheng@linux.alibaba.com> * coroutines.cc (co_await_expander): Simplify. gcc/testsuite 2020-04-10 Bin Cheng <bin.cheng@linux.alibaba.com> * g++.dg/coroutines/co-await-syntax-10.C: New test. * g++.dg/coroutines/co-await-syntax-11.C: New test.
2020-04-09c++: constexpr static data member instantiation [PR94523]Jason Merrill2-4/+15
Here due to my recent change to store_init_value we were expanding the initializer of aw knowing that we were initializing aw. When cxx_eval_call_expression finished the constructor, it wanted to look up the value of aw to set TREE_READONLY on it, but we haven't set DECL_INITIAL yet, so decl_constant_value tried to instantiate the initializer again. And infinite recursion. Stopped by optimizing the case of asking for the value of ctx->object, which is ctx->value. It also would have worked to look in the values hash table, so let's move that up before decl_constant_value as well. gcc/cp/ChangeLog 2020-04-09 Jason Merrill <jason@redhat.com> PR c++/94523 * constexpr.c (cxx_eval_constant_expression) [VAR_DECL]: Look at ctx->object and ctx->global->values first.
2020-04-09c++: Fix wrong paren-init of aggregates interference [PR93790]Marek Polacek3-3/+38
This PR points out that we are rejecting valid code in C++20. The problem is that we were surreptitiously transforming T& t(e) into T& t{e} which is wrong, because the type of e had a conversion function to T, while aggregate initialization of t from e doesn't work. Therefore, I was violating a design principle of P0960, which says that any existing meaning of A(b) should not change. So I think we should only attempt to aggregate-initialize if the original expression was ill-formed. Another design principle is that () should work where {} works, so this: struct S { int i; }; const S& s(1); has to keep working. Thus the special handling for paren-lists with one element. (A paren-list with more than one element would give you "error: expression list treated as compound expression in initializer" C++17.) PR c++/93790 * call.c (initialize_reference): If the reference binding failed, maybe try initializing from { }. * decl.c (grok_reference_init): For T& t(e), set LOOKUP_AGGREGATE_PAREN_INIT but don't build up a constructor yet. * g++.dg/cpp2a/paren-init23.C: New test. * g++.dg/init/aggr14.C: New test.
2020-04-09coroutines: Add cleanups, where required, to statements with captured ↵Iain Sandoe2-7/+20
references. When we promote captured temporaries to local variables, we also remove their initializers from the relevant call expression. This means that we should recompute the need for a cleanup expression once the set of temporaries that remains becomes known. gcc/cp/ChangeLog: 2020-04-08 Iain Sandoe <iain@sandoe.co.uk> Jun Ma <JunMa@linux.alibaba.com> * coroutines.cc (maybe_promote_captured_temps): Add a cleanup expression, if needed, to any call from which we promoted temporaries captured by reference.
2020-04-08c++: Fix ICE-on-invalid with lambda template [PR94507]Marek Polacek2-0/+17
While reducing something else I noticed that we ICE on the following invalid code. In tsubst_lambda_expr, tsubst_template_decl has already reported an error and returned the error_mark_node, so make sure we don't ICE on that. I'm using a goto here because we still have to do finish_struct because it does popclass (). PR c++/94507 - ICE-on-invalid with lambda template. * pt.c (tsubst_lambda_expr): Cope when tsubst_template_decl or tsubst_function_decl returns error_mark_node. * g++.dg/cpp2a/lambda-generic7.C: New test.
2020-04-08Allow new/delete operator deletion only for replaceable.Martin Liska2-0/+21
PR c++/94314 * gimple.c (gimple_call_operator_delete_p): Rename to... (gimple_call_replaceable_operator_delete_p): ... this. Use DECL_IS_REPLACEABLE_OPERATOR_DELETE_P. * gimple.h (gimple_call_operator_delete_p): Rename to ... (gimple_call_replaceable_operator_delete_p): ... this. * tree-core.h (tree_function_decl): Add replaceable_operator flag. * tree-ssa-dce.c (mark_all_reaching_defs_necessary_1): Use DECL_IS_REPLACEABLE_OPERATOR_DELETE_P. (propagate_necessity): Use gimple_call_replaceable_operator_delete_p. (eliminate_unnecessary_stmts): Likewise. * tree-streamer-in.c (unpack_ts_function_decl_value_fields): Pack DECL_IS_REPLACEABLE_OPERATOR. * tree-streamer-out.c (pack_ts_function_decl_value_fields): Unpack the field here. * tree.h (DECL_IS_REPLACEABLE_OPERATOR): New. (DECL_IS_REPLACEABLE_OPERATOR_NEW_P): New. (DECL_IS_REPLACEABLE_OPERATOR_DELETE_P): New. * cgraph.c (cgraph_node::dump): Dump if an operator is replaceable. * ipa-icf.c (sem_item::compare_referenced_symbol_properties): Compare replaceable operator flags. PR c++/94314 * decl.c (duplicate_decls): Duplicate also DECL_IS_REPLACEABLE_OPERATOR. (cxx_init_decl_processing): Mark replaceable all implicitly defined operators. PR c++/94314 * lto-common.c (compare_tree_sccs_1): Compare also DECL_IS_REPLACEABLE_OPERATOR. PR c++/94314 * g++.dg/pr94314-2.C: New test. * g++.dg/pr94314-3.C: New test. * g++.dg/pr94314.C: New test.
2020-04-08c++: Function type and parameter type disagreements [PR92010]Patrick Palka2-37/+123
This resolves parts of Core issues 1001/1322 by rebuilding the function type of an instantiated function template in terms of its formal parameter types whenever the original function type and formal parameter types disagree about the type of a parameter after substitution. gcc/cp/ChangeLog: Core issues 1001 and 1322 PR c++/92010 * pt.c (rebuild_function_or_method_type): Split function out from ... (tsubst_function_type): ... here. (maybe_rebuild_function_decl_type): New function. (tsubst_function_decl): Use it. gcc/testsuite/ChangeLog: Core issues 1001 and 1322 PR c++/92010 * g++.dg/cpp2a/lambda-uneval11.c: New test. * g++.dg/template/array33.C: New test. * g++.dg/template/array34.C: New test. * g++.dg/template/defarg22.C: New test.
2020-04-08c++: Further fix for -fsanitize=vptr [PR94325]Jakub Jelinek2-7/+21
For -fsanitize=vptr, we insert a NULL store into the vptr instead of just adding a CLOBBER of this. build_clobber_this makes the CLOBBER conditional on in_charge (implicit) parameter whenever CLASSTYPE_VBASECLASSES, but when adding this conditionalization to the -fsanitize=vptr code in PR87095, I wanted it to catch some more cases when the class has CLASSTYPE_VBASECLASSES, but the vptr is still not shared with something else, otherwise the sanitization would be less effective. The following testcase shows that the chosen test that CLASSTYPE_PRIMARY_BINFO is non-NULL and has BINFO_VIRTUAL_P set wasn't sufficient, the D class has still sizeof(D) == sizeof(void*) and thus contains just a single vptr, but while in B::~B() this results in the vptr not being cleared, in C::~C() this condition isn't true, as CLASSTYPE_PRIMARY_BINFO in that case is B and is not BINFO_VIRTUAL_P, so it clears the vptr, but the D::~D() dtor after invoking C::~C() invokes A::~A() with an already cleared vptr, which is then reported. The following patch is just a shot in the dark, keep looking through CLASSTYPE_PRIMARY_BINFO until we find BINFO_VIRTUAL_P, but it works on the existing testcase as well as this new one. 2020-04-08 Jakub Jelinek <jakub@redhat.com> PR c++/94325 * decl.c (begin_destructor_body): For CLASSTYPE_VBASECLASSES class dtors, if CLASSTYPE_PRIMARY_BINFO is non-NULL, but not BINFO_VIRTUAL_P, look at CLASSTYPE_PRIMARY_BINFO of its BINFO_TYPE if it is not BINFO_VIRTUAL_P, and so on. * g++.dg/ubsan/vptr-15.C: New test.
2020-04-08c++: ICE with defaulted comparison operator [PR94478]Marek Polacek2-0/+17
Here we ICE because early_check_defaulted_comparison passed a null ctx to same_type_p. The attached test is ill-formed according to [class.compare.default]/1, so fixed by detecting this case early. PR c++/94478 - ICE with defaulted comparison operator * method.c (early_check_defaulted_comparison): Give an error when the context is null. * g++.dg/cpp2a/spaceship-err4.C: New test.
2020-04-08[C/C++, OpenACC] Reject vars of different scope in acc declare (PR94120)Tobias Burnus2-2/+25
gcc/c/ PR middle-end/94120 * c-decl.c (c_check_in_current_scope): New function. * c-tree.h (c_check_in_current_scope): Declare it. * c-parser.c (c_parser_oacc_declare): Add check that variables are declared in the same scope as the directive. Fix handling of namespace vars. gcc/cp/ PR middle-end/94120 * paser.c (cp_parser_oacc_declare): Add check that variables are declared in the same scope as the directive. gcc/testsuite/ PR middle-end/94120 * c-c++-common/goacc/declare-pr94120.c: New. * g++.dg/declare-pr94120.C: New. libgomp/testsuite/ PR middle-end/94120 * libgomp.oacc-c++/declare-pr94120.C: New.
2020-04-08c++: requires-expression and tentative parse [PR94480]Jason Merrill2-0/+6
The problem here was that cp_parser_requires_expression committing to a tentative parse confused cp_parser_decltype_expr, which needs to still be tentative. The only reason to commit here is to get syntax errors within the requires-expression, which we can still do when the commit is firewalled from the enclosing context. gcc/cp/ChangeLog 2020-04-07 Jason Merrill <jason@redhat.com> PR c++/94480 * parser.c (cp_parser_requires_expression): Use tentative_firewall.
2020-04-07c++: ICE on invalid concept placeholder [PR94481].Jason Merrill2-7/+11
Here the 'decltype' is missing '(auto)', so open_paren was NULL, and trying to get its location is a SEGV. Using matching_parens avoids that problem. gcc/cp/ChangeLog 2020-04-07 Jason Merrill <jason@redhat.com> PR c++/94481 * parser.c (cp_parser_placeholder_type_specifier): Use matching_parens.
2020-04-07coroutines, ensure placeholder var is properly declared.Iain Sandoe2-1/+8
In cases that we need to extended the lifetime of a temporary captured by reference, we make a replacement var for the temporary. This will be then used to define a coroutine frame entry (so that the var created is elided by a later phase). However, we should ensure that the var is correctly declared anyway. gcc/cp/ChangeLog: 2020-04-07 Iain Sandoe <iain@sandoe.co.uk> * coroutines.cc (maybe_promote_captured_temps): Ensure that reference capture placeholder vars are properly declared.
2020-04-07c++: Fix usage of CONSTRUCTOR_PLACEHOLDER_BOUNDARY inside array initializers ↵Patrick Palka3-1/+28
[PR90996] This PR reports that ever since the introduction of the CONSTRUCTOR_PLACEHOLDER_BOUNDARY flag, we are sometimes failing to resolve PLACEHOLDER_EXPRs inside array initializers that refer to some inner constructor. In the testcase in the PR, we have as the initializer for "S c[];" the following {{.a=(int &) &_ZGR1c_, .b={*(&<PLACEHOLDER_EXPR struct S>)->a}}} where CONSTRUCTOR_PLACEHOLDER_BOUNDARY is set on the middle constructor. When calling replace_placeholders from store_init_value, we pass the entire initializer to it, and as a result we fail to resolve the PLACEHOLDER_EXPR within due to the CONSTRUCTOR_PLACEHOLDER_BOUNDARY flag on the middle constructor blocking replace_placeholders_r from reaching it. To fix this, we could perhaps either call replace_placeholders in more places, or we could change where we set CONSTRUCTOR_PLACEHOLDER_BOUNDARY. This patch takes this latter approach -- when building up an array initializer, we now bubble any CONSTRUCTOR_PLACEHOLDER_BOUNDARY flag from the element initializers up to the array initializer so that the boundary doesn't later impede us when we call replace_placeholders from store_init_value. Besides fixing the kind of code like in the testcase, this shouldn't cause any other differences in PLACEHOLDER_EXPR resolution because we don't create or use PLACEHOLDER_EXPRs of array type in the frontend, as far as I can tell. gcc/cp/ChangeLog: PR c++/90996 * tree.c (replace_placeholders): Look through all handled components, not just COMPONENT_REFs. * typeck2.c (process_init_constructor_array): Propagate CONSTRUCTOR_PLACEHOLDER_BOUNDARY up from each element initializer to the array initializer. gcc/testsuite/ChangeLog: PR c++/90996 * g++.dg/cpp1y/pr90996.C: New test.
2020-04-07openmp: Fix parallel master error recovery [PR94512]Jakub Jelinek2-1/+7
We need to set OMP_PARALLEL_COMBINED only if the parsing of omp_master succeeded, because otherwise there is no nested master construct in the parallel. 2020-04-07 Jakub Jelinek <jakub@redhat.com> PR c++/94512 * c-parser.c (c_parser_omp_parallel): Set OMP_PARALLEL_COMBINED if c_parser_omp_master succeeded. * parser.c (cp_parser_omp_parallel): Set OMP_PARALLEL_COMBINED if cp_parser_omp_master succeeded. * g++.dg/gomp/pr94512.C: New test.
2020-04-07c++: Fix ICE with implicit operator== [PR94462]Jason Merrill2-2/+8
duplicate_decls assumed that any TREE_ARTIFICIAL function at namespace scope was a built-in function, but now in C++20 it's possible to have an implicitly declared hidden friend operator==. We just need to move the assert into the if condition. gcc/cp/ChangeLog 2020-04-06 Jason Merrill <jason@redhat.com> PR c++/94462 * decl.c (duplicate_decls): Fix handling of DECL_HIDDEN_FRIEND_P.
2020-04-06c++: Fix crash in gimplifier with paren init of aggregates [PR94155]Marek Polacek2-0/+8
Here we crash in the gimplifier because gimplify_init_ctor_eval doesn't expect null indexes for a constructor: /* ??? Here's to hoping the front end fills in all of the indices, so we don't have to figure out what's missing ourselves. */ gcc_assert (purpose); The indexes weren't filled because we never called reshape_init: for a constructor that represents parenthesized initialization of an aggregate we don't allow brace elision or designated initializers. PR c++/94155 - crash in gimplifier with paren init of aggregates. * init.c (build_vec_init): Fill in indexes. * g++.dg/cpp2a/paren-init22.C: New test.
2020-04-04c++: Mangling of dependent conversions [PR91377]Jason Merrill2-0/+6
We skip over other conversion codes when mangling expressions, we should do the same with IMPLICIT_CONV_EXPR. gcc/cp/ChangeLog 2020-04-04 Jason Merrill <jason@redhat.com> PR c++/91377 * mangle.c (write_expression): Skip IMPLICIT_CONV_EXPR.
2020-04-04c++: Refrain from using replace_placeholders in constexpr evaluation [PR94205]Patrick Palka2-8/+30
This removes the use of replace_placeholders in cxx_eval_constant_expression (which is causing the new test lambda-this6.C to ICE due to replace_placeholders mutating the shared TARGET_EXPR_INITIAL tree which then trips up the gimplifier). In its place, this patch adds a 'parent' field to constexpr_ctx which is used to store a pointer to an outer constexpr_ctx that refers to another object under construction. With this new field, we can beef up lookup_placeholder to resolve PLACEHOLDER_EXPRs which refer to former objects under construction, which fixes PR94205 without needing to do replace_placeholders. Also we can now respect the CONSTRUCTOR_PLACEHOLDER_BOUNDARY flag when resolving PLACEHOLDER_EXPRs, and doing so fixes the constexpr analogue of PR79937. gcc/cp/ChangeLog: PR c++/94205 PR c++/79937 * constexpr.c (struct constexpr_ctx): New field 'parent'. (cxx_eval_bare_aggregate): Propagate CONSTRUCTOR_PLACEHOLDER_BOUNDARY flag from the original constructor to the reduced constructor. (lookup_placeholder): Prefer to return the outermost matching object by recursively calling lookup_placeholder on the 'parent' context, but don't cross CONSTRUCTOR_PLACEHOLDER_BOUNDARY constructors. (cxx_eval_constant_expression): Link the 'ctx' context to the 'new_ctx' context via 'new_ctx.parent' when being expanded without an explicit target. Don't call replace_placeholders. (cxx_eval_outermost_constant_expr): Initialize 'ctx.parent' to NULL. gcc/testsuite/ChangeLog: PR c++/94205 PR c++/79937 * g++.dg/cpp1y/pr79937-5.C: New test. * g++.dg/cpp1z/lambda-this6.C: New test.
2020-04-04c++: Fix constexpr evaluation of self-modifying CONSTRUCTORs [PR94219]Patrick Palka2-97/+171
This PR reveals that cxx_eval_bare_aggregate and cxx_eval_store_expression do not anticipate that a constructor element's initializer could mutate the underlying CONSTRUCTOR. Evaluation of the initializer could add new elements to the underlying CONSTRUCTOR, thereby potentially invalidating any pointers to or assumptions about the CONSTRUCTOR's elements, and so these routines should be prepared for that. To fix this problem, this patch makes cxx_eval_bare_aggregate and cxx_eval_store_expression recompute the constructor_elt pointers through which we're assigning, after it evaluates the initializer. Care is taken to to not slow down the common case where the initializer does not modify the underlying CONSTRUCTOR. gcc/cp/ChangeLog: PR c++/94219 PR c++/94205 * constexpr.c (get_or_insert_ctor_field): Split out (while adding support for VECTOR_TYPEs, and optimizations for the common case) from ... (cxx_eval_store_expression): ... here. Rename local variable 'changed_active_union_member_p' to 'activated_union_member_p'. Record the sequence of indexes into 'indexes' that yields the subobject we're assigning to. Record the integer offsets of the constructor indexes we're assigning through into 'index_pos_hints'. After evaluating the initializer of the store expression, recompute 'valp' using 'indexes' and using 'index_pos_hints' as hints. (cxx_eval_bare_aggregate): Tweak comments. Use get_or_insert_ctor_field to recompute the constructor_elt pointer we're assigning through after evaluating each initializer. gcc/testsuite/ChangeLog: PR c++/94219 PR c++/94205 * g++.dg/cpp1y/constexpr-nsdmi3.C: New test. * g++.dg/cpp1y/constexpr-nsdmi4.C: New test. * g++.dg/cpp1y/constexpr-nsdmi5.C: New test. * g++.dg/cpp1z/lambda-this5.C: New test.
2020-04-04c++: Fix invalid pointer-to-member in requires [PR67825]Jason Merrill2-1/+10
A recent change to cmcstl2 led to two tests failing due to this bug: our valid expression checking in the context of a requires-expression wasn't catching that an expression of member function type can only appear as the function operand of a call expression. Fixed by using convert_to_void to do the same checking as a discarded-value expression. This patch also fixes 67825, which already had a testcase, but the testcase was testing for the wrong behavior. gcc/cp/ChangeLog 2020-04-04 Jason Merrill <jason@redhat.com> PR c++/67825 * constraint.cc (tsubst_valid_expression_requirement): Call convert_to_void.
2020-04-04c++: Fix reuse of class constants [PR94453]Jason Merrill3-6/+25
The testcase hit an ICE trying to expand a TARGET_EXPR temporary cached from the other lambda-expression. This patch fixes this in two ways: 1) Avoid reusing a TARGET_EXPR from another function. 2) Avoid ending up with a TARGET_EXPR at all; the use of 'p' had become <TARGET_EXPR<NON_LVALUE_EXPR<TARGET_EXPR ...>>>, which doesn't make any sense. gcc/cp/ChangeLog 2020-04-04 Jason Merrill <jason@redhat.com> PR c++/94453 * constexpr.c (maybe_constant_value): Use break_out_target_exprs. * expr.c (mark_use) [VIEW_CONVERT_EXPR]: Don't wrap a TARGET_EXPR in NON_LVALUE_EXPR.
2020-04-04c++: Fix further protected_set_expr_location related -fcompare-debug issues ↵Jakub Jelinek3-6/+8
[PR94441] My recent protected_set_expr_location changes work well when that function is called unconditionally, but as the testcase shows, the C++ FE has a few spots that do: if (!EXPR_HAS_LOCATION (stmt)) protected_set_expr_location (stmt, locus); or similar. Now, if we have for -g0 stmt of some expression that can have location and has != UNKNOWN_LOCATION, while -g instead has a STATEMENT_LIST containing some DEBUG_BEGIN_STMTs + that expression with that location, we don't call protected_set_expr_location in the -g0 case, but do call it in the -g case, because on the STATEMENT_LIST !EXPR_HAS_LOCATION. The following patch introduces a helper function which digs up the single expression of a STATEMENT_LIST and uses that expression in the EXPR_HAS_LOCATION check (plus changes protected_set_expr_location to also use that helper). Or do we want a further wrapper, perhaps C++ FE only, that would do this protected_set_expr_location_if_unset (stmt, locus)? 2020-04-04 Jakub Jelinek <jakub@redhat.com> PR debug/94441 * tree-iterator.h (expr_single): Declare. * tree-iterator.c (expr_single): New function. * tree.h (protected_set_expr_location_if_unset): Declare. * tree.c (protected_set_expr_location): Use expr_single. (protected_set_expr_location_if_unset): New function. * parser.c (cp_parser_omp_for_loop): Use protected_set_expr_location_if_unset. * cp-gimplify.c (genericize_if_stmt, genericize_cp_loop): Likewise. * g++.dg/opt/pr94441.C: New test.
2020-04-04openmp: Fix ICE on #pragma omp parallel master in template [PR94477]Jakub Jelinek2-1/+9
The following testcase ICEs, because for parallel combined with some other construct we initialize the omp_parallel_combined_clauses pointer and expect the construct combined with it to clear it after it no longer needs it, but OMP_MASTER didn't do that. 2020-04-04 Jakub Jelinek <jakub@redhat.com> PR c++/94477 * pt.c (tsubst_expr) <case OMP_MASTER>: Clear omp_parallel_combined_clauses. * g++.dg/gomp/pr94477.C: New test.
2020-04-03c++: alias template and parameter packs (PR91966).Jason Merrill2-1/+36
In this testcase, when we do a pack expansion of count_better_mins<nums>, nums appears both in the definition of count_better_mins and as its template argument. The intent is that we get a expansion over pairs of elements of the pack, i.e. less<2,2>, less<2,7>, less<7,2>, .... But if we substitute into the definition of count_better_mins when parsing the template, we end up with sum<less<nums,nums>...>, which never gives us less<2,7>. We could deal with this by somehow marking up the use of 'nums' as an argument for 'num', but it's simpler to mark the alias as complex, so we need to instantiate it later with all its arguments rather than replace it early with its expansion. gcc/cp/ChangeLog 2020-04-03 Jason Merrill <jason@redhat.com> PR c++/91966 * pt.c (complex_pack_expansion_r): New. (complex_alias_template_p): Use it.
2020-04-01c++: Fix DMI with lambda 'this' capture [PR94205]Jason Merrill4-2/+16
We represent 'this' in a default member initializer with a PLACEHOLDER_EXPR. Normally in constexpr evaluation when we encounter one it refers to ctx->ctor, but when we're creating a temporary of class type, that replaces ctx->ctor, so a PLACEHOLDER_EXPR that refers to the type of the member being initialized needs to be replaced before that happens. gcc/cp/ChangeLog 2020-03-31 Jason Merrill <jason@redhat.com> PR c++/94205 * constexpr.c (cxx_eval_constant_expression) [TARGET_EXPR]: Call replace_placeholders. * typeck2.c (store_init_value): Fix arguments to fold_non_dependent_expr.
2020-04-01c++: Adjust formatting.Jason Merrill2-49/+60
This patch has no semantic effect; committing it separately makes the change for 94205 easier to read. gcc/cp/ChangeLog 2020-03-31 Jason Merrill <jason@redhat.com> * constexpr.c (cxx_eval_constant_expression) [TARGET_EXPR]: Use local variables.
2020-03-30c++: Fix comparison of fn() and ns::fn() [PR90711]Jason Merrill2-1/+19
The resolution of CWG issue 1321 clarified that when deciding whether two expressions involving template parameters are equivalent, two dependent function calls where the function is named with an unqualified-id are considered to be equivalent if the name is the same, even if unqualified lookup finds different sets of functions. We were wrongly treating qualified-ids the same way, so that EXISTS and test::EXISTS were considered to be equivalent even though they are looking up the name in different scopes. This also causes a mangling bug, but I don't think it's safe to fix that for GCC 10; this patch just fixes the comparison. gcc/cp/ChangeLog 2020-03-30 Jason Merrill <jason@redhat.com> PR c++/90711 * tree.c (cp_tree_equal) [CALL_EXPR]: Compare KOENIG_LOOKUP_P. (called_fns_equal): Check DECL_CONTEXT.
2020-03-30c++: Fix handling of internal fn calls in statement expressions [PR94385]Jakub Jelinek2-1/+8
The following testcase ICEs, because the FE when processing the statement expression changes the .VEC_CONVERT internal fn CALL_EXPR into .PHI call. That is because the internal fn call is recorded in the base.u.ifn field, which overlaps base.u.bits.lang_flag_1 which is used for STMT_IS_FULL_EXPR_P, so this essentially does ifn |= 2 on little-endian. STMT_IS_FULL_EXPR_P bit is used in: cp-gimplify.c- if (STATEMENT_CODE_P (code)) cp-gimplify.c- { cp-gimplify.c- saved_stmts_are_full_exprs_p = stmts_are_full_exprs_p (); cp-gimplify.c- current_stmt_tree ()->stmts_are_full_exprs_p cp-gimplify.c: = STMT_IS_FULL_EXPR_P (*expr_p); cp-gimplify.c- } and pt.c- if (STATEMENT_CODE_P (TREE_CODE (t))) pt.c: current_stmt_tree ()->stmts_are_full_exprs_p = STMT_IS_FULL_EXPR_P (t); so besides being wrong on some other codes, it actually isn't beneficial at all to set it on anything else, so the following patch restricts it to trees with STATEMENT_CODE_P TREE_CODE. 2020-03-30 Jakub Jelinek <jakub@redhat.com> PR c++/94385 * semantics.c (add_stmt): Only set STMT_IS_FULL_EXPR_P on trees with STATEMENT_CODE_P code. * c-c++-common/pr94385.c: New test.
2020-03-28c++: Diagnose when "requires" is used instead of "requires requires" [PR94306]Patrick Palka2-1/+20
This adds support to detect and recover from the case where an opening brace immediately follows the start of a requires-clause. So rather than emitting the error error: expected primary-expression before '{' token followed by a slew of irrevelant errors, we now assume the user had intended to write "requires requires {" and diagnose and recover accordingly. gcc/cp/ChangeLog: PR c++/94306 * parser.c (cp_parser_requires_clause_opt): Diagnose and recover from "requires {" when "requires requires {" was probably intended. gcc/testsuite/ChangeLog: PR c++/94306 * g++.dg/concepts/diagnostic8.C: New test.
2020-03-28c++: requires-expression outside of a template is misevaluated [PR94252]Patrick Palka6-11/+46
This PR shows that a REQUIRES_EXPR outside of a template can sometimes be misevaluated. This happens because the evaluation routine tsubst_requires_expr (and diagnose_requires_expr) assumes the REQUIRES_EXPR's subtrees are templated trees and that therefore it's safe to call tsubst_expr on them. But this assumption isn't valid when we've parsed a REQUIRES_EXPR outside of a template context. In order to make this assumption valid here, this patch sets processing_template_decl to non-zero before parsing the body of a REQUIRES_EXPR so that its subtrees are indeed always templated trees. gcc/cp/ChangeLog: PR c++/94252 * constraint.cc (tsubst_compound_requirement): Always suppress errors from type_deducible_p and expression_convertible_p, as they're not substitution errors. (diagnose_atomic_constraint) <case INTEGER_CST>: Remove this case so that we diagnose INTEGER_CST expressions of non-bool type via the default case. * cp-gimplify.c (cp_genericize_r) <case REQUIRES_EXPR>: New case. * parser.c (cp_parser_requires_expression): Always parse the requirement body as if we're processing a template, by temporarily incrementing processing_template_decl. Afterwards, if we're not actually in a template context, perform semantic processing to diagnose any invalid types and expressions. * pt.c (tsubst_copy_and_build) <case REQUIRES_EXPR>: Remove dead code. * semantics.c (finish_static_assert): Explain an assertion failure when the condition is a REQUIRES_EXPR like we do when it is a concept check. gcc/testsuite/ChangeLog: PR c++/94252 * g++.dg/concepts/diagnostic7.C: New test. * g++.dg/concepts/pr94252.C: New test. * g++.dg/cpp2a/concepts-requires18.C: Adjust to expect an additional diagnostic.
2020-03-28c++: Respect current_constraint_diagnosis_depth in diagnose_compound_requirementPatrick Palka2-9/+23
The previous patch tries to avoid changing our current default diagnostics. But for the sake of consistency we arguably should also respect current_constraint_diagnosis_depth in diagnose_compound_requirement() like we do in the other error-replaying diagnostic routines. But doing so would be a change to our default diagnostics behavior, so the change has been split out into this separate patch for separate consideration. gcc/cp/ChangeLog: * constraint.cc (diagnose_compound_requirement): When diagnosing a compound requirement, maybe replay the satisfaction failure, subject to the current diagnosis depth. gcc/testsuite/ChangeLog: * g++.dg/concepts/diagnostic1.C: Pass -fconcepts-diagnostics-depth=2. * g++.dg/concepts/diagnostic5.C: Adjust expected diagnostics. * g++.dg/cpp2a/concepts-iconv1.C: Pass -fconcepts-diagnostics-depth=2. * g++.dg/cpp2a/concepts-requires5.C: Likewise.
2020-03-28c++: Replay errors during diagnosis of constraint satisfaction failuresPatrick Palka3-20/+157
This patch adds a new flag -fconcepts-diagnostics-depth to the C++ frontend which controls how deeply we replay errors when diagnosing a constraint satisfaction failure. The default is -fconcepts-diagnostics-depth=1 which diagnoses only the topmost constraint satisfaction failure and is consistent with our behavior before this patch. By increasing this flag's value, the user can control how deeply they want the compiler to explain a constraint satisfaction error. For example, if the unsatisfied constraint is a disjunction, then the default behavior is to just say "no branch in the disjunction is satisfied", but with -fconcepts-diagnostics-depth=2 we will additionally replay and diagnose the error in each branch of the disjunction. And if the unsatisfied constraint is a requires expression, then we will replay the error in the requires expression, etc. This proceeds recursively until there is nothing more to replay or we exceeded the maximum depth specified by the flag. Implementation wise, this patch essentially just uncomments the existing commented-out code that performs the error-replaying, and along the way adds logic to keep track of and limit the current replay depth. Besides that, there is a new routine collect_operands_of_disjunction which flattens a disjunction and collects all of its operands into a vector. The extra diagnostics enabled by this flag are at times longer than they need to be (e.g. "the operand is_array_v<...> is unsatisfied because \n the expression is_array_v<...> [with ...] evaluated to false") and not immediately easy to follow (especially when there are nested disjunctions), but the transparency provided by these optional diagnostics seems to be pretty helpful in practice. gcc/c-family/ChangeLog: * c.opt: Add -fconcepts-diagnostics-depth. gcc/cp/ChangeLog: * constraint.cc (finish_constraint_binary_op): Set the location of EXPR as well as its range, because build_x_binary_op doesn't always do so. (current_constraint_diagnosis_depth): New. (concepts_diagnostics_max_depth_exceeded_p): New. (collect_operands_of_disjunction): New. (satisfy_disjunction): When diagnosing a satisfaction failure, maybe replay each branch of the disjunction, subject to the current diagnosis depth. (diagnose_valid_expression): When diagnosing a satisfaction failure, maybe replay the substitution error, subject to the current diagnosis recursion. (diagnose_valid_type): Likewise. (diagnose_nested_requiremnet): Likewise. (diagnosing_failed_constraint::diagnosing_failed_constraint): Increment current_constraint_diagnosis_depth when diagnosing. (diagnosing_failed_constraint::~diagnosing_failed_constraint): Decrement current_constraint_diagnosis_depth when diagnosing. (diagnosing_failed_constraint::replay_errors_p): New static member function. (diagnose_constraints): Don't diagnose if concepts_diagnostics_max_depth is 0. Emit a one-off note to increase -fconcepts-diagnostics-depth if the limit was exceeded. * cp-tree.h (diagnosing_failed_constraint::replay_errors_p): Declare. gcc/testsuite/ChangeLog: * g++.dg/concepts/diagnostic2.C: Expect "no operand" instead of "neither operand". * g++.dg/concepts/diagnostic5.C: New test.