The following code causes an internal compiler error in gcc-10.3 and gcc-11.1. union U { struct { unsigned char a; }; unsigned char b[1]; }; void f(unsigned char a) { union U u = { .a = a }; } Reproducible: Always Steps to Reproduce: 1. Store example code as ice.cpp 2. Compiling with current stable g++ works. g++-10.2.0 -c -o /dev/null ice.cpp 3. Compiling with unstable g++-10.3 or g++11.1 results in internal compiler error. g++-11.1.0 -c -o /dev/null ice.cpp Actual Results: ice.cpp: In function ‘void f(unsigned char)’: ice.cpp:13:30: internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3556 13 | union U u = { .a = a }; | ^ 0x1092ad1 internal_error(char const*, ...) ???:0 0x1092bb8 fancy_abort(char const*, int, char const*) ???:0 0x1103f73 maybe_constant_value(tree_node*, tree_node*, bool) ???:0 0x110a1b2 cp_fully_fold_init(tree_node*) ???:0 0x1194cbb store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc, vl_embed>**, int) ???:0 0x111b691 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int) ???:0 0x1561092 c_parse_file() ???:0 0x158e414 c_common_parse_file() ???:0 Please submit a full bug report, with preprocessed source if appropriate. Please include the complete backtrace with any bug report. See <https://bugs.gentoo.org/> for instructions. Expected Results: Compilation succeeds. This is probably a bug in GCC itself, but the output said to file the bug here. With different compiler options, there are more interesting results: Adding '-ansi` to the command line lets the compilation succeed. Adding '-ansi -pedantic' to the command line lets the compilation succeed and produces the following warnings: ice.cpp:4:9: warning: ISO C++ prohibits anonymous structs [-Wpedantic] 4 | { | ^ ice.cpp: In function ‘void f(unsigned char)’: ice.cpp:13:23: warning: C++ designated initializers only available with ‘-std=c++20’ or ‘-std=gnu++20’ [-Wpedantic] 13 | union U u = { .a = a }; | ^ Adding '-ansi -pedantic -std=gnu++20' to the command line causes the ICE, again.
Nice test case! Happens on gcc master as well: $ LANG=C h g++ -c -o /dev/null ice.cpp ice.cpp: In function 'void f(unsigned char)': ice.cpp:14:24: internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3556 14 | union U u = { .a = a }; | ^ 0x5fed0e get_or_insert_ctor_field /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/constexpr.c:3556 0x68f2a2 cxx_eval_bare_aggregate /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/constexpr.c:4455 0x685466 cxx_eval_constant_expression /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/constexpr.c:6675 0x688030 cxx_eval_outermost_constant_expr /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/constexpr.c:7251 0x68b592 maybe_constant_value(tree_node*, tree_node*, bool) /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/constexpr.c:7525 0x6ab92c cp_fully_fold(tree_node*) /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/cp-gimplify.c:2146 0x6ab92c cp_fully_fold(tree_node*) /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/cp-gimplify.c:2138 0x6ab9d4 cp_fully_fold_init(tree_node*) /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/cp-gimplify.c:2167 0x82219a store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc, vl_embed>**, int) /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/typeck2.c:816 0x6bd08d check_initializer /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/decl.c:7080 0x6d6a8f cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int) /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/decl.c:8014 0x796139 cp_parser_init_declarator /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/parser.c:21891 0x7730ae cp_parser_simple_declaration /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/parser.c:14457 0x77509d cp_parser_declaration_statement /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/parser.c:13592 0x7756ab cp_parser_statement /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/parser.c:11822 0x776eae cp_parser_statement_seq_opt /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/parser.c:12189 0x776f70 cp_parser_compound_statement /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/parser.c:12138 0x794117 cp_parser_function_body /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/parser.c:24080 0x794117 cp_parser_ctor_initializer_opt_and_function_body /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/parser.c:24131 0x79541a cp_parser_function_definition_after_declarator /tmp/portage-tmpdir/portage/sys-devel/gcc-12.0.0_pre9999/work/gcc-12.0.0_pre9999/gcc/cp/parser.c:30068 Please submit a full bug report, with preprocessed source if appropriate. Please include the complete backtrace with any bug report. See <https://bugs.gentoo.org/> for instructions.
Filed upstream bug report as https://gcc.gnu.org/PR100489
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/proj/gcc-patches.git/commit/?id=d9ec8d21d27b98b1ae8a0fe33c8917868a14ba63 commit d9ec8d21d27b98b1ae8a0fe33c8917868a14ba63 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2021-05-20 22:14:05 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2021-05-20 22:14:05 +0000 11.1.0: backport PR100489: union constructor fix Reported-by: Martin Kolleck Bug: https://bugs.gentoo.org/788829 Bug: https://gcc.gnu.org/PR100489 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> 11.1.0/gentoo/28_all_ctor-union-PR100489.patch | 156 +++++++++++++++++++++++++ 11.1.0/gentoo/README.history | 1 + 2 files changed, 157 insertions(+) https://gitweb.gentoo.org/proj/gcc-patches.git/commit/?id=1b262115460489ec8736bfa5102c62656d580fb5 commit 1b262115460489ec8736bfa5102c62656d580fb5 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2021-05-20 22:12:59 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2021-05-20 22:12:59 +0000 10.3.0: backport PR100489: union constructor fix Reported-by: Martin Kolleck Bug: https://bugs.gentoo.org/788829 Bug: https://gcc.gnu.org/PR100489 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> 10.3.0/gentoo/33_all_ctor-union-PR100489.patch | 71 ++++++++++++++++++++++++++ 10.3.0/gentoo/README.history | 3 ++ 2 files changed, 74 insertions(+)
It will take a while to release next gcc patchset in Gentoo (a few weeks). Until them you can try a patch https://gitweb.gentoo.org/proj/gcc-patches.git/plain/11.1.0/gentoo/28_all_ctor-union-PR100489.patch by dropping it to /etc/portage/patches/sys-devel/gcc:11/ and check if it works for you.
Thanks. The patch does work for me.
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/proj/gcc-patches.git/commit/?id=9d40799e2ef69d8650dd59325c0e84b902258b00 commit 9d40799e2ef69d8650dd59325c0e84b902258b00 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2021-06-10 07:28:54 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2021-06-10 07:28:54 +0000 11.1.0: cut 2 patchset Five new patches: + 27_all_msp430-f2c.patch: fix build on 16-bit targets + 28_all_ctor-union-PR100489.patch: fix ICE on some c++ initializers + 29_all_perfect-implicit-PR100644.patch: fix move deletion (fireofx build) + 30_all_arm-lto-ICE-march-mix.patch: fix LTO ICE on arm -march=/-mtune mix + 31_all_ICE-tsubst-PR100102.patch: Bug: https://gcc.gnu.org/PR100361 Bug: https://bugs.gentoo.org/788829 Bug: https://gcc.gnu.org/PR100489 Bug: https://gcc.gnu.org/PR100644 Bug: https://bugs.gentoo.org/792705 Bug: https://gcc.gnu.org/PR100767 Bug: https://bugs.gentoo.org/792291 Bug: https://bugs.gentoo.org/794775 Bug: https://gcc.gnu.org/PR100102 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> 11.1.0/gentoo/README.history | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/proj/gcc-patches.git/commit/?id=4fdc5533816df36a81b6c57dcf7c2233a87f2d46 commit 4fdc5533816df36a81b6c57dcf7c2233a87f2d46 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2021-06-10 07:40:21 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2021-06-10 07:40:21 +0000 10.3.0: cut 2 patchset Five new patches: + 33_all_ctor-union-PR100489.patch: fix ICE on some c++ initializers + 34_all_ICE-tsubst-PR100102.patch: fix ICE in c++ tempate substitution Bug: https://bugs.gentoo.org/788829 Bug: https://gcc.gnu.org/PR100489 Bug: https://bugs.gentoo.org/794775 Bug: https://gcc.gnu.org/PR100102 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> 10.3.0/gentoo/README.history | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=187f062a6f1a768d0e33e0f10c63feb2e74d0b49 commit 187f062a6f1a768d0e33e0f10c63feb2e74d0b49 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2021-06-10 07:49:15 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2021-06-10 07:50:32 +0000 sys-devel/gcc: 10.3.0: cut 2 patchset Two new patches: + 33_all_ctor-union-PR100489.patch: fix ICE on some c++ initializers + 34_all_ICE-tsubst-PR100102.patch: fix ICE in c++ tempate substitution Bug: https://bugs.gentoo.org/788829 Bug: https://gcc.gnu.org/PR100489 Bug: https://bugs.gentoo.org/794775 Bug: https://gcc.gnu.org/PR100102 Package-Manager: Portage-3.0.19, Repoman-3.0.3 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> sys-devel/gcc/Manifest | 1 + sys-devel/gcc/gcc-10.3.0-r1.ebuild | 21 +++++++++++++++++++++ 2 files changed, 22 insertions(+) https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=b250f4243abd49acdd459751ae1e55c995bf9818 commit b250f4243abd49acdd459751ae1e55c995bf9818 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2021-06-10 07:39:30 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2021-06-10 07:50:31 +0000 sys-devel/gcc: 11.1.0: cut 2 patchset Five new patches: + 27_all_msp430-f2c.patch: fix build on 16-bit targets + 28_all_ctor-union-PR100489.patch: fix ICE on some c++ initializers + 29_all_perfect-implicit-PR100644.patch: fix move deletion (fireofx build) + 30_all_arm-lto-ICE-march-mix.patch: fix LTO ICE on arm -march=/-mtune mix + 31_all_ICE-tsubst-PR100102.patch: fix ICE in c++ tempate substitution Bug: https://gcc.gnu.org/PR100361 Bug: https://bugs.gentoo.org/788829 Bug: https://gcc.gnu.org/PR100489 Bug: https://gcc.gnu.org/PR100644 Bug: https://bugs.gentoo.org/792705 Bug: https://gcc.gnu.org/PR100767 Bug: https://bugs.gentoo.org/792291 Bug: https://bugs.gentoo.org/794775 Bug: https://gcc.gnu.org/PR100102 Package-Manager: Portage-3.0.19, Repoman-3.0.3 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> sys-devel/gcc/Manifest | 1 + sys-devel/gcc/gcc-11.1.0-r1.ebuild | 21 +++++++++++++++++++++ 2 files changed, 22 insertions(+)
Should be fixed in gcc-11.1.0-r1 and gcc-10.3.0-r1.
