https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127307
Bug ID: 127307
Summary: ICE & Freeze: Lambda in a CTP type causes the compiler
to either crash or freeze, depending on how you do it
Product: gcc
Version: 16.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: programmer00001h at gmail dot com
Target Milestone: ---
```
template<typename>
using gunpowder = decltype([]{return 0;}());
template<typename T>
struct crash{
template<gunpowder<T>>
struct boom;
};
consteval{
crash<int>::boom<0> _;
}
```
when compiled with `g++ -std=c++26 -freflection crash.cpp`, would cause a
segmentation fault in the compiler:
g++: internal compiler error: Segmentation fault signal terminated program
cc1plus
Segmentation fault (core dumped) g++ -std=c++26 -freflection crash.cpp
When you inline the `gunpowder` template, like so:
```
template<typename>
struct crash{
template<decltype([]{return 0;}())>
struct boom;
};
consteval{
crash<int>::boom<0> _;
}
```
then the compiler freezes (at least for the 10 minutes of patience that I had),
and cc1plus' memory usage rises continuously.
GCC info:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/16/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure
--enable-languages=ada,c,c++,d,fortran,go,lto,m2,objc,obj-c++,rust,cobol
--enable-bootstrap --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://gitlab.archlinux.org/archlinux/packaging/packages/gcc/-/issues
--with-build-config=bootstrap-lto --with-gcc-major-version-only
--with-linker-hash-style=gnu --with-system-zlib --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-fixincludes --disable-libssp
--disable-libstdcxx-pch --disable-werror
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 16.2.1 20260810 (GCC)
