diff --git a/lib/std/process.zig b/lib/std/process.zig index b734276444..4efb58c3df 100644 --- a/lib/std/process.zig +++ b/lib/std/process.zig @@ -2036,7 +2036,8 @@ test createNullDelimitedEnvMap { pub fn createWindowsEnvBlock(allocator: mem.Allocator, env_map: *const EnvMap) ![]u16 { // count bytes needed const max_chars_needed = x: { - var max_chars_needed: usize = 4; // 4 for the final 4 null bytes + // Only need 2 trailing NUL code units for an empty environment + var max_chars_needed: usize = if (env_map.count() == 0) 2 else 1; var it = env_map.iterator(); while (it.next()) |pair| { // +1 for '=' @@ -2060,12 +2061,14 @@ pub fn createWindowsEnvBlock(allocator: mem.Allocator, env_map: *const EnvMap) ! } result[i] = 0; i += 1; - result[i] = 0; - i += 1; - result[i] = 0; - i += 1; - result[i] = 0; - i += 1; + // An empty environment is a special case that requires a redundant + // NUL terminator. CreateProcess will read the second code unit even + // though theoretically the first should be enough to recognize that the + // environment is empty (see https://nullprogram.com/blog/2023/08/23/) + if (env_map.count() == 0) { + result[i] = 0; + i += 1; + } return try allocator.realloc(result, i); }