OK. On 10/8/19 6:14 PM, Marek Polacek wrote:
I've been messing with compare_ics recently and noticed that we don't implement CWG 1601, which should be fairly easy.The motivating example is enum E : char { e }; void f(char); void f(int); void g() { f(e); } where the call to f was ambiguous but we should choose f(char). Currently we give f(int) cr_promotion in standard_conversion, while f(char) remains cr_std, which is worse than cr_promotion. So I thought I'd give it cr_promotion also and then add a tiebreaker to compare_ics. Bootstrapped/regtested on x86_64-linux, ok for trunk? 2019-10-08 Marek Polacek <pola...@redhat.com> PR c++/92032 - DR 1601: Promotion of enum with fixed underlying type. * call.c (standard_conversion): When converting an enumeration with a fixed underlying type to the underlying type, give it the cr_promotion rank. (compare_ics): Implement a tiebreaker as per CWG 1601. * g++.dg/cpp0x/scoped_enum10.C: New test. * g++.dg/cpp0x/scoped_enum11.C: New test. diff --git gcc/cp/call.c gcc/cp/call.c index 6c9acac4614..10172855d4d 100644 --- gcc/cp/call.c +++ gcc/cp/call.c @@ -1484,8 +1484,18 @@ standard_conversion (tree to, tree from, tree expr, bool c_cast_p,conv = build_conv (ck_std, to, conv); - /* Give this a better rank if it's a promotion. */- if (same_type_p (to, type_promotes_to (from)) + tree underlying_type = NULL_TREE; + if (TREE_CODE (from) == ENUMERAL_TYPE + && ENUM_FIXED_UNDERLYING_TYPE_P (from)) + underlying_type = ENUM_UNDERLYING_TYPE (from); + + /* Give this a better rank if it's a promotion. + + To handle CWG 1601, also bump the rank if we are converting + an enumeration with a fixed underlying type to the underlying + type. */ + if ((same_type_p (to, type_promotes_to (from)) + || (underlying_type && same_type_p (to, underlying_type))) && next_conversion (conv)->rank <= cr_promotion) conv->rank = cr_promotion; } @@ -10506,6 +10516,31 @@ compare_ics (conversion *ics1, conversion *ics2) } }+ /* [over.ics.rank]+ + Per CWG 1601: + -- A conversion that promotes an enumeration whose underlying type + is fixed to its underlying type is better than one that promotes to + the promoted underlying type, if the two are different. */ + if (ics1->rank == cr_promotion + && ics2->rank == cr_promotion + && UNSCOPED_ENUM_P (from_type1) + && ENUM_FIXED_UNDERLYING_TYPE_P (from_type1) + && same_type_p (from_type1, from_type2)) + { + tree utype = ENUM_UNDERLYING_TYPE (from_type1); + tree prom = type_promotes_to (from_type1); + if (!same_type_p (utype, prom)) + { + if (same_type_p (to_type1, utype) + && same_type_p (to_type2, prom)) + return 1; + else if (same_type_p (to_type2, utype) + && same_type_p (to_type1, prom)) + return -1; + } + } + /* Neither conversion sequence is better than the other. */ return 0; } diff --git gcc/testsuite/g++.dg/cpp0x/scoped_enum10.C gcc/testsuite/g++.dg/cpp0x/scoped_enum10.C new file mode 100644 index 00000000000..b588581cd3e --- /dev/null +++ gcc/testsuite/g++.dg/cpp0x/scoped_enum10.C @@ -0,0 +1,37 @@ +// PR c++/92032 - DR 1601: Promotion of enumeration with fixed underlying type. +// { dg-do compile { target c++11 } } + +enum E : char { e }; +enum F : int { f }; +enum G : long { g }; +enum H : unsigned { h }; + +int f1(char); +void f1(int); + +void f2(int); +int f2(char); + +int f3(int); +void f3(short); + +int f4(long); +void f4(int); + +void f5(unsigned); +int f5(int); + +int f6(unsigned); +void f6(int); + +void +test () +{ + int r = 0; + r += f1 (e); + r += f2 (e); + r += f3 (f); + r += f4 (g); + r += f5 (f); + r += f6 (h); +} diff --git gcc/testsuite/g++.dg/cpp0x/scoped_enum11.C gcc/testsuite/g++.dg/cpp0x/scoped_enum11.C new file mode 100644 index 00000000000..e6dcfbac9d8 --- /dev/null +++ gcc/testsuite/g++.dg/cpp0x/scoped_enum11.C @@ -0,0 +1,35 @@ +// PR c++/92032 - DR 1601: Promotion of enumeration with fixed underlying type. +// { dg-do compile { target c++11 } } + +enum E1 : long { e1 }; +enum E2 : short { e2 }; + +int f1(short); +void f1(int); + +void f2(int); +int f2(short); + +void f3(int); +int f3(long); + +int f4(short); +void f4(long); + +int f5(int); +void f5(long); + +int f6(unsigned int); // { dg-message "candidate" } +void f6(long); // { dg-message "candidate" } + +void +fn () +{ + int r = 0; + r += f1 (e2); + r += f2 (e2); + r += f3 (e1); + r += f4 (e2); + r += f5 (e2); + r += f6 (e2); // { dg-error "ambiguous" } +}
