https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120563
--- Comment #1 from Anonymous <iamanonymous.cs at gmail dot com> ---
(In reply to Anonymous from comment #0)
> *****************************************************************************
> **
> The compiler produces an internal error during tree_class_check_failed when
> compiling the provided code with the specified options.
> The issue can also be reproduced on Compiler Explorer.
>
> *****************************************************************************
> **
> OS and Platform:
> # uname -a
> Linux ubuntu 4.15.0-213-generic #224-Ubuntu SMP Mon Jun 19 13:30:12 UTC 2023
> x86_64 x86_64 x86_64 GNU/Linux
> *****************************************************************************
> **
> # g++ -v
> Using built-in specs.
> COLLECT_GCC=g++
> COLLECT_LTO_WRAPPER=/root/gdbtest/gcc/gcc-250601/libexec/gcc/x86_64-pc-linux-
> gnu/16.0.0/lto-wrapper
> Target: x86_64-pc-linux-gnu
> Configured with: ../gcc/configure --prefix=/root/gdbtest/gcc/gcc-250601
> --enable-languages=c,c++ --disable-multilib --disable-bootstrap
> Thread model: posix
> Supported LTO compression algorithms: zlib
> gcc version 16.0.0 20250601 (experimental) (GCC)
> *****************************************************************************
> **
> Program:
> #cat code.c
>
>
> #pragma omp declare reduction (+: struct S : merge (&omp_out, &omp_in))
> initializer (init (&omp_priv))
>
> void
> foo (struct S x)
> {
> #pragma omp taskgroup task_reduction (+: x)
> {
> #pragma omp task in_reduction (+: x)
> {
> x.a++;
> x.b++;
> }
> #pragma omp task in_reduction (+: x)
> {
> x.a += 4;
> x.b += 14;
> }
> #pragma omp task in_reduction (+: x)
> {
> x.a += 9;
> x.b += 19;
> }
> }
> if (x.a != 56 || x.b != 86)
> __builtin_abort ();
> }
>
>
> *****************************************************************************
> **
> Command Lines:
> gcc code.c -pipe -MMD -MP -MQ ./ -MT test.o -MF test.d -c -o code_0.o
>
>
> <source>: In function 'omp declare reduction +':
> <source>:1:46: error: implicit declaration of function 'merge'
> [-Wimplicit-function-declaration]
> 1 | #pragma omp declare reduction (+: struct S : merge (&omp_out,
> &omp_in)) initializer (init (&omp_priv))
> | ^~~~~
> <source>:1:86: error: implicit declaration of function 'init'
> [-Wimplicit-function-declaration]
> 1 | #pragma omp declare reduction (+: struct S : merge (&omp_out,
> &omp_in)) initializer (init (&omp_priv))
> |
> ^~~~
> <source>: At top level:
> <source>:4:15: error: parameter 1 ('x') has incomplete type
> 4 | foo (struct S x)
> | ~~~~~~~~~^
> <source>: In function 'foo':
> <source>:6:11: internal compiler error: tree check: expected class 'type',
> have 'exceptional' (error_mark) in c_parser_omp_clause_reduction, at
> c/c-parser.cc:18685
> 6 | #pragma omp taskgroup task_reduction (+: x)
> | ^~~
> 0x2505575 diagnostic_context::diagnostic_impl(rich_location*,
> diagnostic_metadata const*, diagnostic_option_id, char const*, __va_list_tag
> (*) [1], diagnostic_t)
> ???:0
> 0x2526e26 internal_error(char const*, ...)
> ???:0
> 0x8fdebb tree_class_check_failed(tree_node const*, tree_code_class, char
> const*, int, char const*)
> ???:0
> 0xac1cbe c_parse_file()
> ???:0
> 0xb433d9 c_common_parse_file()
> ???:0
> Please submit a full bug report, with preprocessed source (by using
> -freport-bug).
> Please include the complete backtrace with any bug report.
> See <https://gcc.gnu.org/bugs/> for instructions.
> Compiler returned: 1
> *****************************************************************************
> **
>
> Also ICE on trunk, compiler explorer:https://gcc.godbolt.org/z/d6h3n1KKn
>
> *****************************************************************************
> **
Sorry for the mistake, the compile options are '-O0 -fopenmp -Wall -Wextra'.
