[Bug c++/99170] New: [modules] ICE in get_merge_kind with std::string NSDMI

[remi.galanalfonso at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99170

            Bug ID: 99170
           Summary: [modules] ICE in get_merge_kind with std::string NSDMI
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: remi.galanalfonso at gmail dot com
  Target Milestone: ---

Created attachment 50223
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50223&action=edit
preprocessed file

Hello, I ran into the following ICE when testing modules a bit, it doesn't look
like any currently open module bug (reproduced here with a recent trunk, commit
f86e187e12d).

The reproducer is as follows:

$ cat test_modules.cpp 
export module test;

import <string>;

export class A {
        std::string str{"ayyy"};
};

The <string> header unit was compiled with the following:

$ g++ -std=c++20 -fmodules-ts -x c++-system-header string

And the command line used and result are the following (along with -v for
information):

$ g++ -v -save-temps -std=c++20 -fmodules-ts -c test_modules.cpp
Using built-in specs.
COLLECT_GCC=g++
Target: x86_64-pc-linux-gnu
Configured with: ./configure --prefix=/home/remi/Projects/gcc/build-install
--disable-multilib : (reconfigured) ./configure
--prefix=/home/remi/Projects/gcc/build-install --disable-multilib :
(reconfigured) ./configure --prefix=/home/remi/Projects/gcc/build-install
--disable-multilib CC=gcc-9 CXX=g++-9 --enable-languages=c,c++,fortran,lto,objc
--no-create --no-recursion
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.0.0 20210219 (experimental) (GCC) 
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++20' '-fmodules-ts' '-c'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'

/home/remi/Projects/gcc/build-install/libexec/gcc/x86_64-pc-linux-gnu/11.0.0/cc1plus
-E -quiet -v -imultiarch x86_64-linux-gnu -D_GNU_SOURCE test_modules.cpp
-mtune=generic -march=x86-64 -std=c++20 -fmodules-ts -fpch-preprocess -o
test_modules.ii
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/home/remi/Projects/gcc/build-install/lib/gcc/x86_64-pc-linux-gnu/11.0.0/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/home/remi/Projects/gcc/build-install/lib/gcc/x86_64-pc-linux-gnu/11.0.0/../../../../include/c++/11.0.0

/home/remi/Projects/gcc/build-install/lib/gcc/x86_64-pc-linux-gnu/11.0.0/../../../../include/c++/11.0.0/x86_64-pc-linux-gnu

/home/remi/Projects/gcc/build-install/lib/gcc/x86_64-pc-linux-gnu/11.0.0/../../../../include/c++/11.0.0/backward

/home/remi/Projects/gcc/build-install/lib/gcc/x86_64-pc-linux-gnu/11.0.0/include
 /usr/local/include
 /home/remi/Projects/gcc/build-install/include

/home/remi/Projects/gcc/build-install/lib/gcc/x86_64-pc-linux-gnu/11.0.0/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++20' '-fmodules-ts' '-c'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'

/home/remi/Projects/gcc/build-install/libexec/gcc/x86_64-pc-linux-gnu/11.0.0/cc1plus
-fpreprocessed test_modules.ii -quiet -dumpbase test_modules.cpp -dumpbase-ext
.cpp -mtune=generic -march=x86-64 -std=c++20 -version -fmodules-ts -o
test_modules.s
GNU C++20 (GCC) version 11.0.0 20210219 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 11.0.0 20210218 (experimental), GMP version
6.2.1, MPFR version 4.1.0, MPC version 1.2.0, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
GNU C++20 (GCC) version 11.0.0 20210219 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 11.0.0 20210218 (experimental), GMP version
6.2.1, MPFR version 4.1.0, MPC version 1.2.0, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: 8e9853a7486525ef35ca23365b38ea4d
test_modules.cpp:1:9: internal compiler error: in get_merge_kind, at
cp/module.cc:10158
    1 | export module test;
      |         ^~~~~~
0x699387 trees_out::get_merge_kind(tree_node*, depset*)
        ../.././gcc/cp/module.cc:10158
0xa13f63 trees_out::decl_value(tree_node*, depset*)
        ../.././gcc/cp/module.cc:7618
0xa14ebb trees_out::decl_node(tree_node*, walk_kind)
        ../.././gcc/cp/module.cc:8613
0xa15eb2 trees_out::tree_node(tree_node*)
        ../.././gcc/cp/module.cc:9168
0xa1b813 module_state::write_pendings(elf_out*, vec<depset*, va_heap, vl_ptr>,
depset::hash&, unsigned int, unsigned int*)
        ../.././gcc/cp/module.cc:15403
0xa1d050 module_state::write(elf_out*, cpp_reader*)
        ../.././gcc/cp/module.cc:17748
0xa1d71c finish_module_processing(cpp_reader*)
        ../.././gcc/cp/module.cc:19787
0x9b170b c_parse_final_cleanups()
        ../.././gcc/cp/decl2.c:5175
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

The ICE disappears when removing the NSDMI, or when calling the default
constructor instead in the NSDMI.

I have attached the .ii file as advised in https://gcc.gnu.org/bugs/, even
though it doesn't look too interesting in this particular case.