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fix: R_FindPlane aborts on visplane pool exhaustion #162

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fix: R_FindPlane aborts on visplane pool exhaustion #162

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15c8a44
fix: R_FindPlane aborts on visplane pool exhaustion
VedantMadane Aug 24, 2026
6ea8c18
docs: fix R_FindPlane exhaustion doc to match i_error! abort
VedantMadane Sep 1, 2026
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15 changes: 7 additions & 8 deletions room/src/doom/r_plane.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@
use std::ffi::{c_int, c_short, c_uchar};
use std::ptr;

use crate::i_error;
use super::m_fixed::{fixed_t, FixedDiv, FixedMul};
use super::r_sky;
use super::tables;
Expand All @@ -41,7 +42,7 @@ const SCREENHEIGHT: usize = crate::doom::i_video::SCREENHEIGHT as usize;
/// Maximum number of simultaneous visplanes per frame.
///
/// Doom aborts with `I_Error` when this limit is exceeded. The Rust port
/// currently returns a null pointer instead (see [`R_FindPlane`]).
/// aborts via [`i_error!`] when exceeded (see [`R_FindPlane`]).
const MAXVISPLANES: usize = 128;

/// Maximum number of `c_short` slots in the [`openings`] array.
Expand Down Expand Up @@ -546,8 +547,8 @@ pub extern "C" fn R_ClearPlanes() {
/// All sky flats (`picnum == skyflatnum`) share a single visplane at height 0
/// and light level 0.
///
/// Returns a null pointer if the visplane pool (128 entries) is exhausted
/// (the C source would call `I_Error` instead).
/// Aborts via [`crate::i_error!`] if the visplane pool (128 entries) is exhausted
/// (matches the C source `I_Error` path).
///
/// Exported as `#[no_mangle]` for C callers.
///
Expand All @@ -556,9 +557,6 @@ pub extern "C" fn R_ClearPlanes() {
/// Reads and writes the `static mut` globals [`visplanes`], [`lastvisplane`],
/// and [`r_sky::skyflatnum`]. The returned pointer is valid for the lifetime
/// of the current frame (until the next [`R_ClearPlanes`] call).
// FIXME: C aborts with I_Error on MAXVISPLANES overflow; Rust returns null.
// Callers in r_segs dereference the result unconditionally, which will
// cause undefined behavior if the limit is hit.
#[no_mangle]
pub extern "C" fn R_FindPlane(
height: fixed_t,
Expand Down Expand Up @@ -591,8 +589,9 @@ pub extern "C" fn R_FindPlane(
/ std::mem::size_of::<visplane_t>()
>= MAXVISPLANES
{
// Would call I_Error — for now just return null
return ptr::null_mut();
// Match C doomgeneric: abort rather than hand callers a null
// visplane pointer (they dereference unconditionally).
i_error!("R_FindPlane: no more visplanes");
}

let new_vp = lastvisplane;
Expand Down
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