os.date() appends null terminator (\0) to ISO 8601 UTC timestamp in sandboxed Lua 5.4

[Azael-Dev]

What happened?

Starting from FXServer 12767, using os.date("!%Y-%m-%dT%H:%M:%SZ", os.time()) with UTC formatting appends a null terminator (<\0>) at the end of the string.

Expected result

os.date("!%Y-%m-%dT%H:%M:%SZ", os.time()) should return a valid ISO 8601 timestamp without a null terminator (<\0>).

Reproduction steps

1. Run the following Lua script on FXServer 12767+:

    print("ISO 8601 (UTC):", os.date("!%Y-%m-%dT%H:%M:%SZ"))
    print("ISO 8601 (LOCAL):", os.date("%Y-%m-%dT%H:%M:%SZ"))
    print("Standard Date:", os.date("%c"))
    print("YYYY-MM-DD:", os.date("%Y-%m-%d"))
    print("24-hour Time:", os.date("%H:%M:%S"))
    print("12-hour Time:", os.date("%I:%M:%S %p"))
    print("Day of the Week:", os.date("%A"))
    print("Day of the Year:", os.date("%j"))

2. Observe the output (Bug):

    ISO 8601 (UTC):	2025-02-11T07:34:57Z<\0>
    ISO 8601 (LOCAL):	2025-02-11T14:34:57Z
    Standard Date:	Tue Feb 11 14:34:57 2025
    YYYY-MM-DD:	2025-02-11
    24-hour Time:	14:34:57
    12-hour Time:	02:34:57 PM
    Day of the Week:	Tuesday
    Day of the Year:	042
   

3. This issue occurs in sandboxed Lua 5.4 and affects timestamps formatted in ISO 8601 (!%Y-%m-%dT%H:%M:%SZ), causing an unexpected null terminator (<\0>) at the end of the string.

Importancy

There's a workaround

Area(s)

FXServer

Specific version(s)

Server 12767 windows

Additional information

This issue was introduced by commit: 76d4fc0