https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88694
Bug ID: 88694
Summary: constexpr isn't captured correctly in lambda
Product: gcc
Version: 8.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: amosbird at gmail dot com
Target Milestone: ---
Created attachment 45342
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45342&action=edit
source code
This might be related to
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86594
and
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82643
Tested with:
g++ -MMD -MP -DCC_PLAYGROUND -std=c++1z -O2 -v -save-temps
-I/home/amos/git/ccutils/ -I/usr/include -I/usr/local/include -c snippet.cpp -o
snippet.rel.o
Using built-in specs.
COLLECT_GCC=g++
Target: x86_64-pc-linux-gnu
Configured with: ../configure --disable-multilib --with-system-zlib
--enable-languages=c,c++ --enable-gold
Thread model: posix
gcc version 8.2.0 (GCC)
COLLECT_GCC_OPTIONS='-MMD' '-MP' '-D' 'CC_PLAYGROUND' '-std=c++17' '-O2' '-v'
'-save-temps' '-I' '/home/amos/git/ccutils/' '-I' '/usr/include' '-I'
'/usr/local/include' '-c' '-o' 'snippet.rel.o' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
/usr/local/libexec/gcc/x86_64-pc-linux-gnu/8.2.0/cc1plus -E -quiet -v -I
/home/amos/git/ccutils/ -I /usr/include -I /usr/local/include -MMD
snippet.rel.d -MP -MQ snippet.rel.o -D_GNU_SOURCE -D CC_PLAYGROUND snippet.cpp
-mtune=generic -march=x86-64 -std=c++17 -O2 -fpch-preprocess -o snippet.ii
ignoring nonexistent directory
"/usr/local/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../x86_64-pc-linux-gnu/include"
ignoring duplicate directory "/usr/include"
as it is a non-system directory that duplicates a system directory
ignoring duplicate directory "/usr/local/include"
as it is a non-system directory that duplicates a system directory
#include "..." search starts here:
#include <...> search starts here:
/home/amos/git/ccutils/
/usr/local/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../include/c++/8.2.0
/usr/local/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../include/c++/8.2.0/x86_64-pc-linux-gnu
/usr/local/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../include/c++/8.2.0/backward
/usr/local/lib/gcc/x86_64-pc-linux-gnu/8.2.0/include
/usr/local/include
/usr/local/lib/gcc/x86_64-pc-linux-gnu/8.2.0/include-fixed
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-MMD' '-MP' '-D' 'CC_PLAYGROUND' '-std=c++17' '-O2' '-v'
'-save-temps' '-I' '/home/amos/git/ccutils/' '-I' '/usr/include' '-I'
'/usr/local/include' '-c' '-o' 'snippet.rel.o' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
/usr/local/libexec/gcc/x86_64-pc-linux-gnu/8.2.0/cc1plus -fpreprocessed
snippet.ii -quiet -dumpbase snippet.cpp -mtune=generic -march=x86-64
-auxbase-strip snippet.rel.o -O2 -std=c++17 -version -o snippet.s
GNU C++17 (GCC) version 8.2.0 (x86_64-pc-linux-gnu)
compiled by GNU C version 8.2.0, GMP version 6.1.0, MPFR version 3.1.4,
MPC version 1.0.3, isl version isl-0.18-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C++17 (GCC) version 8.2.0 (x86_64-pc-linux-gnu)
compiled by GNU C version 8.2.0, GMP version 6.1.0, MPFR version 3.1.4,
MPC version 1.0.3, isl version isl-0.18-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 4e924b3bd09bf840dfb30b5ba0fbc5b8
snippet.cpp: In instantiation of ‘main()::<lambda(auto:1)> [with auto:1 =
std::integral_constant<int, 0>]’:
snippet.cpp:8:7: required from ‘constexpr void static_for_impl(Func&&,
std::integer_sequence<T, Is ...>) [with T = int; T Begin = 0; Func =
main()::<lambda(auto:1)>; T ...Is = {0, 1, 2}]’
snippet.cpp:12:30: required from ‘constexpr void static_for(Func&&) [with T =
int; T Begin = 0; T End = 3; Func = main()::<lambda(auto:1)>]’
snippet.cpp:21:26: required from here
snippet.cpp:21:49: error: no matching function for call to ‘Foo::print<i>()’
static_for<int, 0, 3>([&](auto i) { [&]() { foo.print<i>(); }(); });
^~~
snippet.cpp:16:27: note: candidate: ‘template<int x> void Foo::print()’
template <int x> void print() { std::cout << x << std::endl; }
^~~~~
snippet.cpp:16:27: note: template argument deduction/substitution failed:
snippet.cpp:21:49: error: ‘this’ is not a constant expression
static_for<int, 0, 3>([&](auto i) { [&]() { foo.print<i>(); }(); });
^~~
snippet.cpp:21:49: note: in template argument for type ‘int’
snippet.cpp: In instantiation of ‘main()::<lambda(auto:1)> [with auto:1 =
std::integral_constant<int, 1>]’:
snippet.cpp:8:7: required from ‘constexpr void static_for_impl(Func&&,
std::integer_sequence<T, Is ...>) [with T = int; T Begin = 0; Func =
main()::<lambda(auto:1)>; T ...Is = {0, 1, 2}]’
snippet.cpp:12:30: required from ‘constexpr void static_for(Func&&) [with T =
int; T Begin = 0; T End = 3; Func = main()::<lambda(auto:1)>]’
snippet.cpp:21:26: required from here
snippet.cpp:21:49: error: no matching function for call to ‘Foo::print<i>()’
snippet.cpp:16:27: note: candidate: ‘template<int x> void Foo::print()’
template <int x> void print() { std::cout << x << std::endl; }
^~~~~
snippet.cpp:16:27: note: template argument deduction/substitution failed:
snippet.cpp:21:49: error: ‘this’ is not a constant expression
static_for<int, 0, 3>([&](auto i) { [&]() { foo.print<i>(); }(); });
^~~
snippet.cpp:21:49: note: in template argument for type ‘int’
snippet.cpp: In instantiation of ‘main()::<lambda(auto:1)> [with auto:1 =
std::integral_constant<int, 2>]’:
snippet.cpp:8:7: required from ‘constexpr void static_for_impl(Func&&,
std::integer_sequence<T, Is ...>) [with T = int; T Begin = 0; Func =
main()::<lambda(auto:1)>; T ...Is = {0, 1, 2}]’
snippet.cpp:12:30: required from ‘constexpr void static_for(Func&&) [with T =
int; T Begin = 0; T End = 3; Func = main()::<lambda(auto:1)>]’
snippet.cpp:21:26: required from here
snippet.cpp:21:49: error: no matching function for call to ‘Foo::print<i>()’
snippet.cpp:16:27: note: candidate: ‘template<int x> void Foo::print()’
template <int x> void print() { std::cout << x << std::endl; }
^~~~~
snippet.cpp:16:27: note: template argument deduction/substitution failed:
snippet.cpp:21:49: error: ‘this’ is not a constant expression
static_for<int, 0, 3>([&](auto i) { [&]() { foo.print<i>(); }(); });
^~~
snippet.cpp:21:49: note: in template argument for type ‘int’
make: *** [snippet.rel.o] Error 1
