[Bug 1945364] Re: C++-20 module: internal compiler error

[Matthias Klose]

** Bug watch added: GCC Bugzilla #108080
   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108080

** Also affects: gcc via
   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108080
   Importance: Unknown
       Status: Unknown

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Title:
  C++-20 module: internal compiler error

Status in gcc:
  Unknown
Status in gcc-11 package in Ubuntu:
  New

Bug description:
  I have a minimal sample project where I try to wrap the spdlog library inside a module unit like so:
  ```
  // spdlog_wrapper.cpp
  module;

  #define SPDLOG_HEADER_ONLY
  #include "spdlog/include/spdlog/spdlog.h"
  #include "spdlog/include/spdlog/sinks/stdout_color_sinks.h"

  export module spdlog_wrapper;

  export int hej() { return 42; }
  ```

  And I compile it like so:
  ```
  g++-11 -std=c++20 -fmodules-ts -I spdlog/include/ -c spdlog_wrapper.cpp
  ```

  I get the following terminal output:

  spdlog_wrapper.cpp:7:8: internal compiler error: in core_vals, at cp/module.cc:6113
      7 | export module spdlog_wrapper;
        |        ^~~~~~
  0xe306b3 internal_error(char const*, ...)
  	???:0
  0xe27039 fancy_abort(char const*, int, char const*)
  	???:0
  0x9e4d4e trees_out::core_vals(tree_node*)
  	???:0
  0x9e5534 trees_out::tree_node_vals(tree_node*)
  	???:0
  0x9e7f49 trees_out::tree_value(tree_node*)
  	???:0
  0x9e6a75 trees_out::tree_node(tree_node*)
  	???:0
  0x9e4fa6 trees_out::core_vals(tree_node*)
  	???:0
  0x9e5534 trees_out::tree_node_vals(tree_node*)
  	???:0
  0x9e59f6 trees_out::decl_value(tree_node*, depset*)
  	???:0
  0x9e93f8 depset::hash::find_dependencies(module_state*)
  	???:0
  0x9ec92d module_state::write(elf_out*, cpp_reader*)
  	???:0
  0xf9fe8e c_parse_final_cleanups()
  	???:0
  Please submit a full bug report,
  with preprocessed source if appropriate.
  Please include the complete backtrace with any bug report.
  See <file:///usr/share/doc/gcc-11/README.Bugs> for instructions.
  make: *** [Makefile:4: spdlog_wrapper] Error 1


  Some additional information:

  $ g++-11 --version
  > g++-11 (Ubuntu 11.1.0-1ubuntu1~20.04) 11.1.0

  $ lsb_release -a
  > No LSB modules are available.
  > Distributor ID:	Ubuntu
  > Description:		Ubuntu 20.04.2 LTS
  > Release:		20.04
  > Codename:		focal

  
  I have experienced the exact same error (or VERY similar in terms of terminal error message)
  when trying to compile the xxhash.hpp library header into a BMI directly.
  Even though that's a different error, perhaps there is some overlap?

  
  Kind regards,
  Alexander

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