Patch submitted: https://gcc.gnu.org/ml/gcc-patches/2018-10/msg00452.html [C++ PATCH] Fix pretty-print of enumerator ids (PR c++/87364)
My first GCC patch attempt, so more eyes would be good. Cheers, Will On Tue, Sep 25, 2018 at 4:25 PM will wray <wjw...@gmail.com> wrote: > BTW The bug is still UNCONFIRMED > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87364 > > It is easy to CONFIRM: > > Follow this Compiler Explorer link https://godbolt.org/z/P4ejiy > or paste this code into a file and compile with g++: > > template <auto> struct wauto; > enum e { a }; > wauto<a> v; // error > > > Note that GCC reports error: ... 'wauto<e(0)> v' > => It should report error: ... 'wauto<a> v' > > This is a bug; the intent of the code is print the enumerator id > (clang prints the enumerator id and so do recent MSVC previews). > There is also test code linked to the bug covering more cases. > > I'd appreciate if someone would confirm the bug. > > Thanks, Will > > On Mon, Sep 24, 2018 at 5:23 PM will wray <wjw...@gmail.com> wrote: > >> Thanks Nathan, >> >> >> In fact, after testing with enums nested in namespaces or structs, >> >> or function local, I realised nested specifiers should be printed >> >> for both scoped and unscoped enums, but for unscoped enums one >> >> level of nested specifier (the enum type) needs to be stripped. >> >> So I inverted the IS_SCOPED test and used get_containing_scope: >> >> >> if (value != NULL_TREE) >> { >> >> if (!ENUM_IS_SCOPED (type)) >> >> type = get_containing_scope (type); >> >> pp_cxx_nested_name_specifier (pp, type); >> >> pp->id_expression (TREE_PURPOSE (value)); >> >> } >> >> >> I submitted this fix as a patch to the bug report, with tests. >> >> With this fix GCC now has similar output to both Clang and MSVC >> for enumerated values. For non-enumerated values GCC continues >> to print a C-style cast while Clang & MSVC print plain digits. >> Yay! GCC is winning! (gives type info for non-enumerated values). >> >> A downside of nested specifiers is that output gets verbose. >> >> Richard Smith suggests to use less verbose output for known types >> compared to auto deduced types. Discussion starts here >> http://lists.llvm.org/pipermail/cfe-dev/2018-September/059229.html >> >> For enum args, I guess that this would mean distinguishing whether >> the corresponding template parameter was auto or a given enum type >> and only printing a simple id with no nested specs for given type. >> I don't know yet if that info is available at the leaf level here. >> >> Similarly, type info should be added to deduced Integral values. >> I may start to investigate how to do this in GCC pretty print. >> I submitted the related request to MSVC devs: >> >> https://developercommunity.visualstudio.com/content/problem/339663/improve-pretty-print-of-integral-non-type-template.html >> >> > given the code base ... >> >> GCC pretty-print code was committed by GDR mid 2002, >> K&R style C, updated to C90 'prototype' in mid 2003, >> untouched since then, not for C++11 or C++17 enum updates. >> >> I found this corner of the code base fairly easy to hack, >> thanks perhaps to GDRs attempts to follow the grammar. >> >> >> On Mon, Sep 24, 2018 at 3:53 PM Nathan Sidwell <nat...@acm.org> wrote: >> >>> On 9/19/18 7:41 AM, will wray wrote: >>> > Re: "Pretty print of enumerator never prints the id, >>> > always falls back to C-style cast output" >>> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87364 >>> > >>> >>> > I have a fix which duplicates the code in pp_c_enumeration_constant >>> > to pp_cxx_enumeration_constant in cxx-pretty print, with modification >>> > >>> > if (value != NULL_TREE) >>> > { >>> > if (ENUM_IS_SCOPED (type)) >>> > pp_cxx_nested_name_specifier (pp, type); >>> > pp->id_expression (TREE_PURPOSE (value)); >>> > } >>> > >>> > This works in my testing so far, but >>> > - It duplicates code from c to cxx (not DRY 'Don't Repeat Yourself) >>> > - I didn't find a single function to print full nested, scoped id >>> > so had to check if ENUM_IS_SCOPED to output nested specifiers. >>> >>> This seems a fine approach, given the code base. >>> >>> nathan >>> >>> -- >>> Nathan Sidwell >>> >>
