This is not the right list. Bug reports should go to bugzilla, and discussion of changes/fixes to GCC code should go to the gcc mailing list. On Wed, 19 Sep 2018 at 13:49, will wray <wjwray@xxxxxxxxx> wrote: > > Also, the docs need a fix. > The GCC Internals doc is inconsistent on enumerator value. > > GCC Internals https://gcc.gnu.org/onlinedocs/gccint.pdf > Chapter 11 GENERIC 11.3 Types (p 158 of current pdf): > > ENUMERAL_TYPE > Used to represent an enumeration type > ... the TREE_VALUE will be an INTEGER_CST giving the value > assigned to that constant... > > *This is incorrect - TREE_VALUE is not an INTEGER_CST - > this is the bug in gcc enumerator pretty print.* > > Chapter 11 GENERIC 11.4 Declarations (p 161) > > CONST_DECL > These nodes are used to represent enumeration constants. > The value of the constant is given by DECL_INITIAL which > will be an INTEGER_CST with the same type as the TREE_TYPE > of the CONST_DECL, i.e., an ENUMERAL_TYPE. > > *This is correct - DECL_INITIAL is needed to get the value* > > My guess is that DECL_INITIAL was introduced at some point > but not all the code and docs were updated for the change. > > > On Tue, Sep 18, 2018 at 3:58 PM will wray <wjwray@xxxxxxxxx> wrote: > > > There's a bug in gcc pretty printing of C / C++ enumerators: > > > > GCC should print the id of an enumerated value > > but prints a C-style cast (the fallback for non-enumerated values) > > > > The bug shows up in __PRETTY_FUNCTION__ output, for instance. > > You can see it in the error output of this Compiler Explorer example > > https://godbolt.org/z/1df0Sk > > > > enum e { a, b, c=0 }; > > template <auto> struct wauto; // deliberately incomplete to trigger.. > > wauto<a> v; // error: aggregate 'wauto<(e)0> v' has incomplete type.. > > > > The error output should print 'a' in place of '(e)0' > > > > (Clang gets it right with 'wauto<a>', > > MSVC wrongly prints 'wauto<0>' so also loses type information.) > > > > This mail shows a one-line hack to fix the bug... almost... > > I'd like advice or assistance towards a proper fix. > > > > The function is ~30 lines of code so I paste it after an intro. > > > > The intent of the code is to print, for a given integral constant: > > > > - The enum id of the first enumerator with that value, or > > - a C-style cast if no enumerator is found with that value. > > > > In c-pretty-print.c > > c_pretty_printer::constant calls pp_c_enumeration_constant > > > > /******************** pp_c_enumeration_constant ****************/ > > > > /* Attempt to print out an ENUMERATOR. Return true on success. > > Else return false; that means the value was obtained by a cast, > > in which case print out the type-id part of the cast-expression > > -- the casted value is then printed by pp_c_integer_literal. */ > > > > static bool > > pp_c_enumeration_constant (c_pretty_printer *pp, tree e) > > { > > bool value_is_named = true; > > tree type = TREE_TYPE (e); > > tree value; > > > > /* Find the name of this constant. */ > > for (value = TYPE_VALUES (type); > > value != NULL_TREE && !tree_int_cst_equal (TREE_VALUE (value), e); > > value = TREE_CHAIN (value)) > > ; > > > > if (value != NULL_TREE) > > pp->id_expression (TREE_PURPOSE (value)); > > else > > { > > /* Value must have been cast. */ > > pp_c_type_cast (pp, type); > > value_is_named = false; > > } > > > > return value_is_named; > > } > > /***************************************************************/ > > The code iterates over the enumerators, comparing with the given value, > > prints the id if found else falls back to print the C-style cast. > > However, the comparison always fails so it always prints the cast > > (after iterating over all the enumerators) and never the id. > > > > The comparison in the enumeration loop can be fixed by adding DECL_INITIAL > > to 'unwrap' the enumerator's value so it compares correctly as INTEGER_CST, > > terminating the loop and pretty-printing the id instead of the C-style > > cast. > > > > /* Find the name of this constant. */ > > for (value = TYPE_VALUES (type); > > value != NULL_TREE && !tree_int_cst_equal (DECL_INITIAL( TREE_VALUE > > (value)), e); > > ^^^^^^^^^^^^^ > > ^ > > value = TREE_CHAIN (value)) > > ; > > > > With this patch, the loop exits early when it finds an enumerator of the > > given value and prints the found-enumerator's id via: > > > > if (value != NULL_TREE) > > pp->id_expression (TREE_PURPOSE (value)); > > > > However... > > This code is located in c-pretty-print.c > > and has not been updated to deal with C++11 scoped enums. > > > > I can share a more complete fix that duplicates c-pretty-print.c > > code to cxx-pretty-print.c and modifies it for scoped enums. > > I'm learning as I hack but would like guidance on a proper fix > > from anyone more familiar with gcc pretty print and/or grammar - > > the guideline comment, at the top of the file, states: > > > > /* The pretty-printer code is primarily designed to closely follow > > (GNU) C and C++ grammars... */ > > > > Another thought. > > The pretty-printing code will need an overhaul for C++20 with > > the proposed changes for generalised non-type template args. > > > > Thanks for any pointers. > > > >
