From 15c0a2a9305648095f5586a02b5a5017e1643e99 Mon Sep 17 00:00:00 2001 From: Artemiy Volkov Date: Mon, 20 Mar 2017 13:47:57 -0700 Subject: [PATCH] Add rvalue references to overloading resolution This patch introduces changes to rank_one_type() dealing with ranking an rvalue reference type when selecting a best viable function from a set of candidate functions. The 4 new added rules for rvalue references are: 1) An rvalue argument cannot be bound to a non-const lvalue reference parameter and an lvalue argument cannot be bound to an rvalue reference parameter. [C++11 13.3.3.1.4p3] 2) If a conversion to one type of reference is an identity conversion, and a conversion to the second type of reference is a non-identity conversion, choose the first type. [C++11 13.3.3.2p3] 3) An rvalue should be first tried to bind to an rvalue reference, and then to an lvalue reference. [C++11 13.3.3.2p3] 4) An lvalue reference to a function gets higher priority than an rvalue reference to a function. [C++11 13.3.3.2p3] This patch is not exactly correct. See c++/15372 for tracking overload resolution bugs. gdb/ChangeLog PR gdb/14441 * gdbtypes.c (rank_one_type): Implement overloading resolution rules regarding rvalue references. --- gdb/ChangeLog | 6 ++++++ gdb/gdbtypes.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 61 insertions(+), 3 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index c5ebe6f6a7c..2f4449477d3 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2017-03-20 Artemiy Volkov + + PR gdb/14441 + * gdbtypes.c (rank_one_type): Implement overloading + resolution rules regarding rvalue references. + 2017-03-20 Artemiy Volkov PR gdb/14441 diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c index defc00d34e5..6f3aeabc173 100644 --- a/gdb/gdbtypes.c +++ b/gdb/gdbtypes.c @@ -58,6 +58,8 @@ const struct rank VOID_PTR_CONVERSION_BADNESS = {2,0}; const struct rank BOOL_CONVERSION_BADNESS = {3,0}; const struct rank BASE_CONVERSION_BADNESS = {2,0}; const struct rank REFERENCE_CONVERSION_BADNESS = {2,0}; +const struct rank LVALUE_REFERENCE_TO_RVALUE_BINDING_BADNESS = {5,0}; +const struct rank DIFFERENT_REFERENCE_TYPE_BADNESS = {6,0}; const struct rank NULL_POINTER_CONVERSION_BADNESS = {2,0}; const struct rank NS_POINTER_CONVERSION_BADNESS = {10,0}; const struct rank NS_INTEGER_POINTER_CONVERSION_BADNESS = {3,0}; @@ -3611,15 +3613,65 @@ rank_one_type (struct type *parm, struct type *arg, struct value *value) { struct rank rank = {0,0}; - if (types_equal (parm, arg)) - return EXACT_MATCH_BADNESS; - /* Resolve typedefs */ if (TYPE_CODE (parm) == TYPE_CODE_TYPEDEF) parm = check_typedef (parm); if (TYPE_CODE (arg) == TYPE_CODE_TYPEDEF) arg = check_typedef (arg); + if (value != NULL) + { + /* An rvalue argument cannot be bound to a non-const lvalue + reference parameter... */ + if (VALUE_LVAL (value) == not_lval + && TYPE_CODE (parm) == TYPE_CODE_REF + && !TYPE_CONST (parm->main_type->target_type)) + return INCOMPATIBLE_TYPE_BADNESS; + + /* ... and an lvalue argument cannot be bound to an rvalue + reference parameter. [C++ 13.3.3.1.4p3] */ + if (VALUE_LVAL (value) != not_lval + && TYPE_CODE (parm) == TYPE_CODE_RVALUE_REF) + return INCOMPATIBLE_TYPE_BADNESS; + } + + if (types_equal (parm, arg)) + return EXACT_MATCH_BADNESS; + + /* An lvalue reference to a function should get higher priority than an + rvalue reference to a function. */ + + if (value != NULL && TYPE_CODE (arg) == TYPE_CODE_RVALUE_REF + && TYPE_CODE (TYPE_TARGET_TYPE (arg)) == TYPE_CODE_FUNC) + { + return (sum_ranks (rank_one_type (parm, + lookup_pointer_type (TYPE_TARGET_TYPE (arg)), NULL), + DIFFERENT_REFERENCE_TYPE_BADNESS)); + } + + /* If a conversion to one type of reference is an identity conversion, and a + conversion to the second type of reference is a non-identity conversion, + choose the first type. */ + + if (value != NULL && TYPE_IS_REFERENCE (parm) && TYPE_IS_REFERENCE (arg) + && TYPE_CODE (parm) != TYPE_CODE (arg)) + { + return (sum_ranks (rank_one_type (TYPE_TARGET_TYPE (parm), + TYPE_TARGET_TYPE (arg), NULL), DIFFERENT_REFERENCE_TYPE_BADNESS)); + } + + /* An rvalue should be first tried to bind to an rvalue reference, and then to + an lvalue reference. */ + + if (value != NULL && TYPE_CODE (parm) == TYPE_CODE_REF + && VALUE_LVAL (value) == not_lval) + { + if (TYPE_IS_REFERENCE (arg)) + arg = TYPE_TARGET_TYPE (arg); + return (sum_ranks (rank_one_type (TYPE_TARGET_TYPE (parm), arg, NULL), + LVALUE_REFERENCE_TO_RVALUE_BINDING_BADNESS)); + } + /* See through references, since we can almost make non-references references. */ -- 2.30.2