set_prop max_size/min_size with an unparsable value (e.g. "unset") aborts Hyprland: throws const char* past catch(std::exception&)

[magnusriga]

Hyprland version

Hyprland 0.56.2 built from branch v0.56.2 at commit efb50993780079460b0cbed1363e2166a2de1d9f (Arch package hyprland 0.56.2-4)

Also present on main as of f469351 (2026-10-27).

Description

Setting max_size or min_size through hl.dsp.window.set_prop with a value that is not a valid size expression aborts the compositor. The value "unset" triggers it, because unset is only handled by parsePropTrivial, not by the size props. Any unparsable value should return an error instead.

Reproduce (crashes the session):

hyprctl dispatch 'hl.dsp.window.set_prop({window="address:0x<addr>", prop="max_size", value="unset"})'

Cause

In src/config/shared/actions/ConfigActions.cpp, Actions::setProp, the max_size and min_size branches do:

if (!SIZE) {
    Log::logger->log(Log::ERR, "failed to parse {} as an expression", VAL);
    throw "failed to parse expression";
}

That throws a const char*, but the enclosing handler is catch (std::exception& e), so the exception is not caught. It unwinds through lua_pcallk (from CConfigManager::eval, called by the hyprctl handler) and reaches std::terminate, giving SIGABRT.

Trimmed backtrace (two identical crashes):

#9  __cxa_throw (libstdc++)
#10 Hyprland(+0x264012)
#11 Hyprland(+0xb22ce9)
#16 lua_pcallk (liblua 5.5)
#17 Config::Lua::CConfigManager::guardedPCall
#26 Config::Lua::CConfigManager::eval
#29 CHyprCtl::getReply
#31 wl_event_loop_dispatch

Suggested fix

Return the error instead of throwing a non-std::exception, e.g. return std::unexpected(std::format("failed to parse {} as an expression", VAL));, or throw std::runtime_error. Optionally accept "unset" for max_size / min_size to clear the override, matching the other props.

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⚠️ Strike 1/3 issued to @magnusriga by system.