https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98475
Bug ID: 98475 Summary: Class template argument deduction for alias templates fails Product: gcc Version: 10.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: kimhappy at hanyang dot ac.kr Target Milestone: --- Created attachment 49857 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49857&action=edit Example case [Environment] OS: Arch Linux on Windows 10 x86_64 Kernel: 4.19.128-microsoft-standard [Compile command] g++ -std=c++20 -Wall -Wextra [Output] test.cpp: In function ‘int main()’: test.cpp:15:21: internal compiler error: Segmentation fault 15 | auto o1 = SSS(10); | ^ Please submit a full bug report, with preprocessed source if appropriate. See <https://bugs.archlinux.org/> for instructions. [Output of g++ -v] Using built-in specs. COLLECT_GCC=g++ COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/ --enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --with-isl --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-install-libiberty --enable-linker-build-id --enable-lto --enable-multilib --enable-plugin --enable-shared --enable-threads=posix --disable-libssp --disable-libstdcxx-pch --disable-libunwind-exceptions --disable-werror gdc_include_dir=/usr/include/dlang/gdc Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 10.2.0 (GCC) [Description] Class template argument deduction for alias templates fails with some cases. I tested it in various environments, but the results were the same. In example case that I attached, if I replace T3 with a non-template template argument or remove the second constructor of SS, it compiles fine.