[Bug c++/124478] New: Failed to read module cache at compile time

[printfne at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124478

            Bug ID: 124478
           Summary: Failed to read module cache at compile time
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: printfne at gmail dot com
  Target Milestone: ---

/// tools.cppm
export module tools;
import std;

export struct DedupeFilesPath {
    std::vector<std::string> other_files;
};


/// minhash.cppm
export module dedupe:minhash;

export struct FileMinHash {
    friend class LSH;
    int file_minhash;
};


/// lsh.cppm
export module dedupe:lsh;
import :minhash;
import std;
import tools;

export struct LSH {
    FileMinHash lsh;

    std::vector<DedupeFilesPath> dedupe() {
        lsh.file_minhash;
        return {};
    }
};

/// dedupe.cppm
export module dedupe;
export import :lsh;
export import :minhash;

/// text.cppm
export module text;
import std;
import tools;
import dedupe;

export DedupeFilesPath analyse_text(const std::string& path) {
    return {};
}


/// main.cppm
import text;

int main() {
    analyse_text("/test/path");
    return 0;
}

/// command 
mkdir build && cd build
g++-latest -std=c++26 -fmodules -c -fsearch-include-path bits/std.cc
g++-latest -std=c++26 -fmodules -c ../tools.cppm
g++-latest -std=c++26 -fmodules -c ../minhash.cppm
g++-latest -std=c++26 -fmodules -c ../lsh.cppm
g++-latest -std=c++26 -fmodules -c ../dedupe.cppm
g++-latest -std=c++26 -fmodules ../main.cpp

/// error message
In module imported at ../text.cppm:4:1,
of module text, imported at ../main.cpp:1:
dedupe: error: failed to read compiled module cluster 36: Bad file data
dedupe: note: compiled module file is ‘gcm.cache/dedupe.gcm’
dedupe: error: failed to read compiled module cluster 37: Bad file data
dedupe: error: failed to read compiled module cluster 38: Bad file data
dedupe: error: failed to read compiled module cluster 40: Bad file data
dedupe: error: failed to read compiled module cluster 41: Bad file data
dedupe: error: failed to read compiled module cluster 42: Bad file data
../main.cpp:4:17: fatal error: failed to load pendings for ‘std::vector’
    4 |     analyse_text("/test/path");
      |     ~~~~~~~~~~~~^~~~~~~~~~~~~~
compilation terminated.

/// g++ version
g++ (GCC) 16.0.1 20260220 (experimental)