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* [Bug c++/108414] New: template meta programming @ 2023-01-16 6:30 amewo22370 at gmail dot com 2023-01-16 6:40 ` [Bug c++/108414] " pinskia at gcc dot gnu.org ` (5 more replies) 0 siblings, 6 replies; 7+ messages in thread From: amewo22370 at gmail dot com @ 2023-01-16 6:30 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108414 Bug ID: 108414 Summary: template meta programming Product: gcc Version: 12.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: amewo22370 at gmail dot com Target Milestone: --- Created attachment 54276 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54276&action=edit archive with source code and preprocessed files gcc of version 12.2.0 and linux 5.15.83-1-lts I have attached the source code. If you compile test code with line 36 commented out and line 37 uncommented, then the compiler gives an error. But if you uncomment line 36 and comment out line 37, the compiler compiles the code without errors, but the result is incorrect. Description of the code: template alias 'template<std::size_t I, typename T> using nth_type_t;' must return type with index I, that contains in type list 'T'. Comilator commands: gcc -v -save-temps -std=c++20 -lstdc++ test_line36.cpp -o test_line36 gcc -v -save-temps -std=c++20 -lstdc++ test_line37.cpp -o test_line37 Also added attachments according to bug reporting instructions. Compilation error with 'gcc -v -save-temps -std=c++20 -lstdc++ test_line37.cpp -o test_line37': Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/12.2.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /build/gcc/src/gcc/configure --enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --enable-bootstrap --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/ --with-build-config=bootstrap-lto --with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit --enable-cet=auto --enable-checking=release --enable-clocale=gnu --enable-default-pie --enable-default-ssp --enable-gnu-indirect-function --enable-gnu-unique-object --enable-libstdcxx-backtrace --enable-link-serialization=1 --enable-linker-build-id --enable-lto --enable-multilib --enable-plugin --enable-shared --enable-threads=posix --disable-libssp --disable-libstdcxx-pch --disable-werror Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 12.2.0 (GCC) COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++20' '-o' 'test_line37' '-mtune=generic' '-march=x86-64' /usr/lib/gcc/x86_64-pc-linux-gnu/12.2.0/cc1plus -E -quiet -v -D_GNU_SOURCE test_line37.cpp -mtune=generic -march=x86-64 -std=c++20 -fpch-preprocess -o test_line37.ii ignoring nonexistent directory "/usr/lib/gcc/x86_64-pc-linux-gnu/12.2.0/../../../../x86_64-pc-linux-gnu/include" #include "..." search starts here: #include <...> search starts here: /usr/lib/gcc/x86_64-pc-linux-gnu/12.2.0/../../../../include/c++/12.2.0 /usr/lib/gcc/x86_64-pc-linux-gnu/12.2.0/../../../../include/c++/12.2.0/x86_64-pc-linux-gnu /usr/lib/gcc/x86_64-pc-linux-gnu/12.2.0/../../../../include/c++/12.2.0/backward /usr/lib/gcc/x86_64-pc-linux-gnu/12.2.0/include /usr/local/include /usr/lib/gcc/x86_64-pc-linux-gnu/12.2.0/include-fixed /usr/include End of search list. COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++20' '-o' 'test_line37' '-mtune=generic' '-march=x86-64' /usr/lib/gcc/x86_64-pc-linux-gnu/12.2.0/cc1plus -fpreprocessed test_line37.ii -quiet -dumpbase test_line37.cpp -dumpbase-ext .cpp -mtune=generic -march=x86-64 -std=c++20 -version -o test_line37.s GNU C++20 (GCC) version 12.2.0 (x86_64-pc-linux-gnu) compiled by GNU C version 12.2.0, GMP version 6.2.1, MPFR version 4.1.0-p13, MPC version 1.2.1, isl version isl-0.25-GMP warning: MPFR header version 4.1.0-p13 differs from library version 4.1.1-p1. warning: MPC header version 1.2.1 differs from library version 1.3.0. GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 GNU C++20 (GCC) version 12.2.0 (x86_64-pc-linux-gnu) compiled by GNU C version 12.2.0, GMP version 6.2.1, MPFR version 4.1.0-p13, MPC version 1.2.1, isl version isl-0.25-GMP warning: MPFR header version 4.1.0-p13 differs from library version 4.1.1-p1. warning: MPC header version 1.2.1 differs from library version 1.3.0. GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 Compiler executable checksum: 402ce889a414e2a3abbbe3146fa0a6cb test_line37.cpp: In substitution of ‘template<long unsigned int I, class T> using nth_type_t = typename nth_type::type [with long unsigned int I = 0; T = type_list<int, float, double>]’: test_line37.cpp:49:36: required from here test_line37.cpp:41:7: error: no type named ‘type’ in ‘struct nth_type<0, type_list<int, float, double> >’ 41 | using nth_type_t = typename nth_type<I, T>::type; | ^~~~~~~~~~ test_line37.cpp: In substitution of ‘template<long unsigned int I, class T> using nth_type_t = typename nth_type::type [with long unsigned int I = 1; T = type_list<int, float, double>]’: test_line37.cpp:50:36: required from here test_line37.cpp:41:7: error: no type named ‘type’ in ‘struct nth_type<1, type_list<int, float, double> >’ test_line37.cpp: In substitution of ‘template<long unsigned int I, class T> using nth_type_t = typename nth_type::type [with long unsigned int I = 2; T = type_list<int, float, double>]’: test_line37.cpp:51:36: required from here test_line37.cpp:41:7: error: no type named ‘type’ in ‘struct nth_type<2, type_list<int, float, double> >’ test_line37.cpp: In function ‘int main()’: test_line37.cpp:53:25: error: ‘elm0’ was not declared in this scope 53 | std::cout << typeid(elm0).name() << std::endl; | ^~~~ test_line37.cpp:54:25: error: ‘elm1’ was not declared in this scope 54 | std::cout << typeid(elm1).name() << std::endl; | ^~~~ test_line37.cpp:55:25: error: ‘elm2’ was not declared in this scope 55 | std::cout << typeid(elm2).name() << std::endl; | ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/108414] template meta programming 2023-01-16 6:30 [Bug c++/108414] New: template meta programming amewo22370 at gmail dot com @ 2023-01-16 6:40 ` pinskia at gcc dot gnu.org 2023-01-16 7:00 ` amewo22370 at gmail dot com ` (4 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-01-16 6:40 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108414 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |c++-lambda, rejects-valid --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- > using nth_element_t = typename decltype([]<typename T>(const indexed<I, T>&){return std::type_identity<T>{};}(make_indexer<Ts...>()))::type; There are some known issue with lambda inside a decltype which seems like might be causing issues here ... ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/108414] template meta programming 2023-01-16 6:30 [Bug c++/108414] New: template meta programming amewo22370 at gmail dot com 2023-01-16 6:40 ` [Bug c++/108414] " pinskia at gcc dot gnu.org @ 2023-01-16 7:00 ` amewo22370 at gmail dot com 2023-01-16 9:35 ` redi at gcc dot gnu.org ` (3 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: amewo22370 at gmail dot com @ 2023-01-16 7:00 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108414 --- Comment #2 from Евгений Лисицын <amewo22370 at gmail dot com> --- (In reply to Andrew Pinski from comment #1) > > using nth_element_t = typename decltype([]<typename T>(const indexed<I, T>&){return std::type_identity<T>{};}(make_indexer<Ts...>()))::type; > > There are some known issue with lambda inside a decltype which seems like > might be causing issues here ... interesting that 'typedef' and 'using' have different behavior ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/108414] template meta programming 2023-01-16 6:30 [Bug c++/108414] New: template meta programming amewo22370 at gmail dot com 2023-01-16 6:40 ` [Bug c++/108414] " pinskia at gcc dot gnu.org 2023-01-16 7:00 ` amewo22370 at gmail dot com @ 2023-01-16 9:35 ` redi at gcc dot gnu.org 2023-01-16 9:40 ` [Bug c++/108414] Incorrect pack expansion as argument to lambda redi at gcc dot gnu.org ` (2 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: redi at gcc dot gnu.org @ 2023-01-16 9:35 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108414 --- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Reduced: using size_t = decltype(sizeof(0)); template<typename T> struct type_identity { using type = T; }; template<typename T, typename U> constexpr bool is_same_v = false; template<typename T> constexpr bool is_same_v<T, T> = true; template<typename... Ts> struct type_list {}; template <size_t I, typename T> struct indexed { using type = T; }; template <size_t I, typename ...Ts> struct indexer; template <size_t I, typename T, typename ...Ts> struct indexer<I, T, Ts...> : indexed<I, T>, indexer<I+1, Ts...> {}; template <size_t I, typename T> struct indexer<I, T> : indexed<I, T> {}; template <size_t I, typename ...Ts> using nth_element_t = typename decltype([]<typename T>(const indexed<I, T>&){return type_identity<T>{};}(indexer<0, Ts...>{}))::type; template<size_t I, typename T> struct nth_type; template<size_t I, typename ... Ts> struct nth_type< I, type_list<Ts...> > { #ifndef USING typedef nth_element_t<I, Ts...> type; // Incorrect result with it #else using type = nth_element_t<I, Ts...>; // Compile error #endif }; template<size_t I, typename T> using nth_type_t = typename nth_type<I, T>::type; using list = type_list<int, float, double>; using elm0 = nth_type_t<0, list>; using elm1 = nth_type_t<1, list>; using elm2 = nth_type_t<2, list>; static_assert( is_same_v<elm0, int> ); static_assert( is_same_v<elm1, float> ); static_assert( is_same_v<elm2, double> ); Without -DUSING nth.cc:47:16: error: static assertion failed 47 | static_assert( is_same_v<elm1, float> ); | ^~~~~~~~~~~~~~~~~~~~~~ nth.cc:48:16: error: static assertion failed 48 | static_assert( is_same_v<elm2, double> ); | ^~~~~~~~~~~~~~~~~~~~~~~ With -DUSING nth.cc: In substitution of 'template<long unsigned int I, class T> using nth_type_t = typename nth_type::type [with long unsigned int I = 0; T = type_list<int, float, double>]': nth.cc:42:32: required from here nth.cc:38:7: error: no type named 'type' in 'struct nth_type<0, type_list<int, float, double> >' 38 | using nth_type_t = typename nth_type<I, T>::type; | ^~~~~~~~~~ nth.cc: In substitution of 'template<long unsigned int I, class T> using nth_type_t = typename nth_type::type [with long unsigned int I = 1; T = type_list<int, float, double>]': nth.cc:43:32: required from here nth.cc:38:7: error: no type named 'type' in 'struct nth_type<1, type_list<int, float, double> >' nth.cc: In substitution of 'template<long unsigned int I, class T> using nth_type_t = typename nth_type::type [with long unsigned int I = 2; T = type_list<int, float, double>]': nth.cc:44:32: required from here nth.cc:38:7: error: no type named 'type' in 'struct nth_type<2, type_list<int, float, double> >' nth.cc:46:26: error: 'elm0' was not declared in this scope 46 | static_assert( is_same_v<elm0, int> ); | ^~~~ nth.cc:46:16: error: template argument 1 is invalid 46 | static_assert( is_same_v<elm0, int> ); | ^~~~~~~~~~~~~~~~~~~~ nth.cc:47:26: error: 'elm1' was not declared in this scope 47 | static_assert( is_same_v<elm1, float> ); | ^~~~ nth.cc:47:16: error: template argument 1 is invalid 47 | static_assert( is_same_v<elm1, float> ); | ^~~~~~~~~~~~~~~~~~~~~~ nth.cc:48:26: error: 'elm2' was not declared in this scope 48 | static_assert( is_same_v<elm2, double> ); | ^~~~ nth.cc:48:16: error: template argument 1 is invalid 48 | static_assert( is_same_v<elm2, double> ); | ^~~~~~~~~~~~~~~~~~~~~~~ ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/108414] Incorrect pack expansion as argument to lambda 2023-01-16 6:30 [Bug c++/108414] New: template meta programming amewo22370 at gmail dot com ` (2 preceding siblings ...) 2023-01-16 9:35 ` redi at gcc dot gnu.org @ 2023-01-16 9:40 ` redi at gcc dot gnu.org 2023-03-27 10:13 ` yagreg7 at gmail dot com 2024-04-13 8:16 ` pinskia at gcc dot gnu.org 5 siblings, 0 replies; 7+ messages in thread From: redi at gcc dot gnu.org @ 2023-01-16 9:40 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108414 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2023-01-16 Ever confirmed|0 |1 Status|UNCONFIRMED |NEW Summary|template meta programming |Incorrect pack expansion as | |argument to lambda --- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- This works with or without -DUSING when -DNAMED_FUNCTION is used: using size_t = decltype(sizeof(0)); template<typename T> struct type_identity { using type = T; }; template<typename T, typename U> constexpr bool is_same_v = false; template<typename T> constexpr bool is_same_v<T, T> = true; template<typename... Ts> struct type_list {}; template <size_t I, typename T> struct indexed { using type = T; }; template <size_t I, typename ...Ts> struct indexer; template <size_t I, typename T, typename ...Ts> struct indexer<I, T, Ts...> : indexed<I, T>, indexer<I+1, Ts...> {}; template <size_t I, typename T> struct indexer<I, T> : indexed<I, T> {}; #ifndef NAMED_FUNCTION template <size_t I, typename ...Ts> using nth_element_t = typename decltype([]<typename T>(const indexed<I, T>&){return type_identity<T>{};}(indexer<0, Ts...>{}))::type; #else template<size_t I, typename T> auto select(const indexed<I, T>&) { return type_identity<T>{}; } template <size_t I, typename ...Ts> using nth_element_t = typename decltype(select<I>(indexer<0, Ts...>{}))::type; #endif template<size_t I, typename T> struct nth_type; template<size_t I, typename ... Ts> struct nth_type< I, type_list<Ts...> > { #ifndef USING typedef nth_element_t<I, Ts...> type; // Incorrect result with it #else using type = nth_element_t<I, Ts...>; // Compile error #endif }; template<size_t I, typename T> using nth_type_t = typename nth_type<I, T>::type; using list = type_list<int, float, double>; using elm0 = nth_type_t<0, list>; using elm1 = nth_type_t<1, list>; using elm2 = nth_type_t<2, list>; static_assert( is_same_v<elm0, int> ); static_assert( is_same_v<elm1, float> ); static_assert( is_same_v<elm2, double> ); So as Andrew said, the problem is the lambda in the decltype expression. ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/108414] Incorrect pack expansion as argument to lambda 2023-01-16 6:30 [Bug c++/108414] New: template meta programming amewo22370 at gmail dot com ` (3 preceding siblings ...) 2023-01-16 9:40 ` [Bug c++/108414] Incorrect pack expansion as argument to lambda redi at gcc dot gnu.org @ 2023-03-27 10:13 ` yagreg7 at gmail dot com 2024-04-13 8:16 ` pinskia at gcc dot gnu.org 5 siblings, 0 replies; 7+ messages in thread From: yagreg7 at gmail dot com @ 2023-03-27 10:13 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108414 Gregory Dushkin <yagreg7 at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |yagreg7 at gmail dot com --- Comment #5 from Gregory Dushkin <yagreg7 at gmail dot com> --- I have two more much shorter examples of this problem: https://godbolt.org/z/EWb3ToK6E https://godbolt.org/z/fh5Tjax1z The first one reveals that inside of a concept `decltype` of a lambda that comes via a type alias will be evaluated to `int` (revealed with `#if 0` and `-fconcepts-diagnostics-depth=2`). With `#if 1` it produces ``` <source>:17:32: error: template argument 1 is invalid 17 | concept ConceptTest = std::same_as<GetArg<T>, PT>; ``` The second example is probably one of the shortest ones to reveal this problem. Both compile successfully with `clang trunk` and `msvc v19.latest` but don't with `gcc trunk` It would be really nice to see this issue resolved to be able to create type helpers without cluttering the `detail` namespace :) ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/108414] Incorrect pack expansion as argument to lambda 2023-01-16 6:30 [Bug c++/108414] New: template meta programming amewo22370 at gmail dot com ` (4 preceding siblings ...) 2023-03-27 10:13 ` yagreg7 at gmail dot com @ 2024-04-13 8:16 ` pinskia at gcc dot gnu.org 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu.org @ 2024-04-13 8:16 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108414 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |FIXED Target Milestone|--- |14.0 --- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Fixed on the trunk for GCC 14 by the recent lambda template patches. ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2024-04-13 8:17 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-01-16 6:30 [Bug c++/108414] New: template meta programming amewo22370 at gmail dot com 2023-01-16 6:40 ` [Bug c++/108414] " pinskia at gcc dot gnu.org 2023-01-16 7:00 ` amewo22370 at gmail dot com 2023-01-16 9:35 ` redi at gcc dot gnu.org 2023-01-16 9:40 ` [Bug c++/108414] Incorrect pack expansion as argument to lambda redi at gcc dot gnu.org 2023-03-27 10:13 ` yagreg7 at gmail dot com 2024-04-13 8:16 ` pinskia at gcc dot gnu.org
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