Rime plugin 需求可执行权限的必要性

[hosiet]

（本 issue 来源于 #518 ，以及 libera.chat #fcitx 频道 2021-12-30 的讨论）

我在作为 Debian Developer 维护 Debian 中的 librime 时注意到以下代码：

librime/plugins/plugins_module.cc

Lines 35 to 46 in bc589fd

	const fs::perms exe_perms = (fs::owner_exe | fs::group_exe | fs::others_exe);
	ModuleManager& mm = ModuleManager::instance();
	if (!fs::is_directory(plugins_dir)) {
	return;
	}
	LOG(INFO) << "loading plugins from " << plugins_dir;
	for (fs::directory_iterator iter(plugins_dir), end; iter != end; ++iter) {
	fs::path plugin_file = iter->path();
	if (plugin_file.extension() == boost::dll::shared_library::suffix()) {
	fs::file_status plugin_file_status = fs::status(plugin_file);
	if (fs::is_regular_file(plugin_file_status) &&
	fs::status(plugin_file).permissions() & exe_perms) {

如上所示，目前 librime 仅在 plugin 文件具有可执行权限时才尝试加载。但现代 Linux 系统中并无 shared library 一定具有可执行权限的规定。特别地对于 deb 系发行版，Debian Policy ( https://www.debian.org/doc/debian-policy/ch-sharedlibs.html ) 有 shared library 不应添加 executable bit 的规定：

Shared libraries should not be installed executable, since the dynamic linker does not require this and trying to execute a shared library usually results in a core dump.

当前 librime 明确检查插件文件是否可执行，这可能导致部分 Linux 发行版的插件无法得到识别。且如不考虑发行版问题，检查是否可执行的意义不明确，似乎是多此一举。如果检查插件是否可执行没有特别的意义，我建议采纳 #518 的修改。

参考：

• https://unix.stackexchange.com/questions/40587/why-are-shared-libraries-executable

[Arfrever]

As original author of #431, maybe I thought that executable permission is needed (for plugins loaded by dlopen function which is internally used by boost::dll::shared_library), but apparently it may be dependent on operating system (according to discussion from above URL, executable permission would be needed on HP-UX operating system).

Instead of dropping check for permissions, it may be better to check for readable permission.

[lotem]

Merged be0ea83

Thanks.

On checking readable permission:
Non-readable plugin executable shouldn't be considered a supported case. I prefer logging an error to silently skipping it.

[Arfrever]

I also wonder if maybe it would make sense to ignore hidden files (whose names start with .):

    if (plugin_file.filename().string()[0] != '.' &&
        plugin_file.extension() == boost::dll::shared_library::suffix()) {