https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119807
Bug ID: 119807
Summary: constexpr counter thing causes ICE: in
instantiate_decl, at cp/pt.cc:27844
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: eczbek.void at gmail dot com
Target Milestone: ---
https://godbolt.org/z/zaTaEWesh
Works fine with Clang
```
using size_t = decltype(0uz);
template<auto tag, size_t current>
struct CounterReader {
template<typename>
friend auto counterFlag(CounterReader<tag, current>) noexcept;
};
template<auto tag, size_t current>
struct CounterWriter {
static constexpr size_t value = current;
template<typename>
friend auto counterFlag(CounterReader<tag, current>) noexcept {}
};
template<auto tag, auto unique, size_t current = 0, size_t mask = 1uz <<
(sizeof(size_t) * 8 - 1)>
[[nodiscard]] constexpr size_t counterAdvance() noexcept {
if constexpr (!mask) {
return CounterWriter<tag, current + 1>::value;
} else if constexpr (requires { counterFlag<void>(CounterReader<tag,
current | mask>()); }) {
return counterAdvance<tag, unique, current | mask, (mask >>
1)>();
}
else {
return counterAdvance<tag, unique, current, (mask >> 1)>();
}
}
constexpr auto defaultCounterTag = [] {};
template<auto tag = defaultCounterTag, auto unique = [] {}>
constexpr size_t counter() noexcept {
return counterAdvance<tag, unique>();
}
int main() {
static_assert(counter() == 1);
static_assert(counter() == 2);
}
```
```
Using built-in specs.
COLLECT_GCC=/opt/compiler-explorer/gcc-snapshot/bin/g++
Target: x86_64-linux-gnu
Configured with: ../gcc-trunk-20250414/configure
--prefix=/opt/compiler-explorer/gcc-build/staging
--enable-libstdcxx-backtrace=yes --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu --disable-bootstrap
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--enable-multilib --enable-clocale=gnu
--enable-languages=c,c++,fortran,ada,objc,obj-c++,go,d,rust,m2,cobol
--enable-ld=yes --enable-gold=yes --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-linker-build-id --enable-lto
--enable-plugins --enable-threads=posix
--with-pkgversion=Compiler-Explorer-Build-gcc-d72b4e9f78f841a032538070a035177cc4f20d68-binutils-2.42
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 15.0.1 20250414 (experimental)
(Compiler-Explorer-Build-gcc-d72b4e9f78f841a032538070a035177cc4f20d68-binutils-2.42)
COLLECT_GCC_OPTIONS='-fdiagnostics-color=always' '-g' '-o' '/app/output.s'
'-masm=intel' '-fno-verbose-asm' '-S' '-std=c++23' '-v' '-freport-bug'
'-shared-libgcc' '-mtune=generic' '-march=x86-64' '-dumpdir' '/app/'
/opt/compiler-explorer/gcc-trunk-20250414/bin/../libexec/gcc/x86_64-linux-gnu/15.0.1/cc1plus
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/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/x86_64-linux-gnu/15.0.1/
-D_GNU_SOURCE <source> -quiet -dumpdir /app/ -dumpbase output.cpp -dumpbase-ext
.cpp -masm=intel -mtune=generic -march=x86-64 -g -std=c++23 -version
-fdiagnostics-color=always -fno-verbose-asm -freport-bug -o /app/output.s
GNU C++23
(Compiler-Explorer-Build-gcc-d72b4e9f78f841a032538070a035177cc4f20d68-binutils-2.42)
version 15.0.1 20250414 (experimental) (x86_64-linux-gnu)
compiled by GNU C version 11.4.0, GMP version 6.2.1, MPFR version
4.1.0, MPC version 1.2.1, isl version isl-0.24-GMP
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
ignoring nonexistent directory
"/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/x86_64-linux-gnu/15.0.1/../../../../x86_64-linux-gnu/include"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/15.0.1/../../../../include/c++/15.0.1"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/15.0.1/../../../../include/c++/15.0.1/x86_64-linux-gnu"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/15.0.1/../../../../include/c++/15.0.1/backward"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/15.0.1/include"
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/15.0.1/include-fixed/x86_64-linux-gnu"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/15.0.1/include-fixed"
ignoring nonexistent directory
"/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/15.0.1/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/x86_64-linux-gnu/15.0.1/../../../../include/c++/15.0.1
/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/x86_64-linux-gnu/15.0.1/../../../../include/c++/15.0.1/x86_64-linux-gnu
/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/x86_64-linux-gnu/15.0.1/../../../../include/c++/15.0.1/backward
/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/x86_64-linux-gnu/15.0.1/include
/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/x86_64-linux-gnu/15.0.1/include-fixed/x86_64-linux-gnu
/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/x86_64-linux-gnu/15.0.1/include-fixed
/usr/local/include
/opt/compiler-explorer/gcc-trunk-20250414/bin/../lib/gcc/../../include
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
Compiler executable checksum: 3d92deed85ed5a39b231c772fe6d397c
<source>: In instantiation of 'constexpr size_t counterAdvance() [with auto tag
= <lambda closure object><lambda()>(); auto unique = <lambda closure
object><lambda()>(); long unsigned int current = 0; long unsigned int mask =
9223372036854775808; size_t = long unsigned int]':
<source>:33:36: required from here
33 | return counterAdvance<tag, unique>();
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
<source>:38:23: in 'constexpr' expansion of 'counter<>()'
<source>:21:58: internal compiler error: in instantiate_decl, at cp/pt.cc:27844
21 | } else if constexpr (requires {
counterFlag<void>(CounterReader<tag, current | mask>()); }) {
|
~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
0x29272c5 diagnostic_context::diagnostic_impl(rich_location*,
diagnostic_metadata const*, diagnostic_option_id, char const*, __va_list_tag
(*) [1], diagnostic_t)
???:0
0x293e296 internal_error(char const*, ...)
???:0
0xad02dc fancy_abort(char const*, int, char const*)
???:0
0xbd78b3 maybe_instantiate_decl(tree_node*)
???:0
0xbd95a7 mark_used(tree_node*, int)
???:0
0xb078ce build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
???:0
0xd74726 finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
bool, int)
???:0
0xb58536 tsubst_requires_expr(tree_node*, tree_node*, int, tree_node*)
???:0
0xd1e2fd instantiate_decl(tree_node*, bool, bool)
???:0
0xb4cef2 maybe_constant_value(tree_node*, tree_node*, mce_value)
???:0
0xdc2cae cp_build_binary_op(op_location_t const&, tree_code, tree_node*,
tree_node*, int)
???:0
0xb0a644 build_new_op(op_location_t const&, tree_code, int, tree_node*,
tree_node*, tree_node*, tree_node*, tree_node**, int)
???:0
0xdb41e2 build_x_binary_op(op_location_t const&, tree_code, tree_node*,
tree_code, tree_node*, tree_code, tree_node*, tree_node**, int)
???:0
0xcf38e3 c_parse_file()
???:0
0xe56059 c_common_parse_file()
???:0
Please submit a full bug report, with preprocessed source.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Preprocessed source stored into /tmp/ccshEkd0.out file, please attach this to
your bugreport.
Compiler returned: 1
```
