https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93324
Bug ID: 93324
Summary: [10 Regression] ICE with -Wall on constexpr if
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc-bugs at marehr dot dialup.fu-berlin.de
Target Milestone: ---
The following code works on gcc 9 and below, but ICEs on gcc10 with -Wall.
```
struct
{
template <int>
static constexpr bool a() { return 0; }
} e;
template <typename>
void d()
{
auto c(e);
using b = decltype(c);
if constexpr (b::a<2>());
}
```
See godbolt: https://godbolt.org/z/3wEnL7
```
> g++-git -std=c++17 -Wall -c ice.cpp
ice.cpp: In function ‘void d()’:
ice.cpp:12:26: internal compiler error: Segmentation fault
12 | if constexpr (b::a<2>());
| ^
0xc7230f crash_signal
/home/marehr/Packages/gcc-git/src/gcc/gcc/toplev.c:328
0x783eca fndecl_built_in_p(tree_node const*, built_in_class)
/home/marehr/Packages/gcc-git/src/gcc/gcc/tree.h:6208
0x783eca fndecl_built_in_p(tree_node const*, unsigned int, built_in_class)
/home/marehr/Packages/gcc-git/src/gcc/gcc/tree.h:6217
0x783eca is_std_constant_evaluated_p
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/semantics.c:737
0x783eca finish_if_stmt_cond(tree_node*, tree_node*)
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/semantics.c:771
0x71bfcb cp_parser_selection_statement
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:11898
0x71bfcb cp_parser_statement
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:11261
0x71c8f8 cp_parser_statement_seq_opt
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:11745
0x71c9b0 cp_parser_compound_statement
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:11699
0x7325b0 cp_parser_function_body
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:22907
0x7325b0 cp_parser_ctor_initializer_opt_and_function_body
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:22958
0x735cad cp_parser_function_definition_after_declarator
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:28745
0x736ca7 cp_parser_function_definition_from_specifiers_and_declarator
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:28661
0x736ca7 cp_parser_init_declarator
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:20536
0x73b7b4 cp_parser_single_declaration
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:29236
0x73b93d cp_parser_template_declaration_after_parameters
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:28808
0x73beea cp_parser_explicit_template_declaration
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:29074
0x73f0f9 cp_parser_declaration
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:13277
0x73f6d8 cp_parser_translation_unit
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:4723
0x73f6d8 c_parse_file()
/home/marehr/Packages/gcc-git/src/gcc/gcc/cp/parser.c:43569
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://bugs.archlinux.org/> for instructions.
```
This code compiles when removing the -Wall flag.
```
> g++-git -v
Using built-in specs.
COLLECT_GCC=g++-git
COLLECT_LTO_WRAPPER=/opt/gcc/gcc-git/bin/../lib/gcc/x86_64-pc-linux-gnu/10.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /home/marehr/Packages/gcc-git/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++ --enable-shared --enable-threads=posix
--with-system-zlib --with-isl --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-clocale=gnu --disable-libstdcxx-pch
--disable-libssp --enable-gnu-unique-object --enable-linker-build-id
--enable-lto --enable-plugin --enable-install-libiberty
--with-linker-hash-style=gnu --enable-gnu-indirect-function --enable-multilib
--disable-werror --enable-checking=release --enable-default-pie
--enable-default-ssp --enable-cet=auto --disable-boostrap
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.0.1 20200116 (experimental) (GCC)
```
