Failed to read data if data/cache exists

[ehughsbaird]

Describe the bug

ERROR : src/cata_utility.cpp:554 [std::optional<std::string> read_whole_file(const std::filesystem::path &)] Failed to read from "data/json/npcs/godco/members/NPC_Olwen_Powell.json": opening file failed
INFO : Fail to initialize global game state
Failed to read data/json/npcs/godco/members/NPC_Olwen_Powell.json
terminate called after throwing an instance of 'std::filesystem::__cxx11::filesystem_error'
  what():  filesystem error: cannot remove all: Too many open files [test_user_dir/save/Test World 测试世 界 1087607]
zsh: IOT instruction (core dumped)  tests/cata_test 'force_load_game'

Attach save file

N/A

Steps to reproduce

1. rm -r data/cache
2. tests/cata_test 'force_load_game' - no error
3. tests/cata_test 'force_load_game' - error

Expected behavior

data/cache works as a cache and does not prevent the game from loading.

Screenshots

No response

Versions and configuration

8d698f8

Linux

Additional context

No response

[ehughsbaird]

17fd4db80a9b8a00e6718eab633b77699f139e94 is the first bad commit
commit 17fd4db80a9b8a00e6718eab633b77699f139e94
Author: akrieger <akrieger@users.noreply.github.com>
Date:   Sun Jun 8 21:31:09 2025 -0400

    Writeable mmapped file interface, with resizing function.

 src/flexbuffer_cache.cpp |   4 +-
 src/mmap_file.cpp        | 303 ++++++++++++++++++++++++++++++++---------------
 src/mmap_file.h          |  49 ++++++--
 3 files changed, 250 insertions(+), 106 deletions(-)

17fd4db from #78857

[akrieger]

Trying to reproduce.

[akrieger]

/confirmed