From f9c6a0549503f00a1ab0ad58a98a30ee99b96770 Mon Sep 17 00:00:00 2001
From: Leon Anavi <leon.anavi@konsulko.com>
Date: Thu, 9 Jul 2026 11:37:04 +0000
Subject: [PATCH] Ppmd7/Ppmd8: Fix SIGABRT in OutputBuffer_Grow

The decode loop could abort in OutputBuffer_Grow() when a resumed
decode thread wrote past the current call's max_length. Stop early
once that limit is reached instead of trying to grow the buffer
further.

Also fix Ppmd8Decoder_decode because it never updated needs_input
when input was fully consumed, unlike Ppmd7.

Fixes test_ppmd7_decode_chunks and the equivalent Ppmd8 case,
which previously aborted deterministically partway through decoding
testdata2.ppmd in small chunks.

This work was sponsored by GOVCERT.LU.

Upstream-Status: Pending [https://github.com/miurahr/pyppmd/pull/131/]

Signed-off-by: Leon Anavi <leon.anavi@konsulko.com>
---
 src/ext/_ppmdmodule.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/ext/_ppmdmodule.c b/src/ext/_ppmdmodule.c
index dafa1c5..94f7f18 100644
--- a/src/ext/_ppmdmodule.c
+++ b/src/ext/_ppmdmodule.c
@@ -531,6 +531,12 @@ Ppmd7Decoder_decode(Ppmd7Decoder *self,  PyObject *args, PyObject *kwargs) {
             break;
         }
         if (out->pos == out->size) {
+            /* Already reached max_length for this call; stop instead of
+               growing (avoids rest<=0 assert in OutputBuffer_Grow) */
+            if (self->blocksOutputBuffer->max_length >= 0 &&
+                self->blocksOutputBuffer->allocated >= self->blocksOutputBuffer->max_length) {
+                break;
+            }
             if (OutputBuffer_Grow(self->blocksOutputBuffer, out) < 0) {
                 PyErr_SetString(PyExc_ValueError, "No Memory.");
                 goto error;
@@ -1276,6 +1282,11 @@ Ppmd8Decoder_decode(Ppmd8Decoder *self,  PyObject *args, PyObject *kwargs) {
              break;  // filled expected
         }
         if (out->pos == out->size) {
+            /* Same guard as for Ppmd7Decoder_decode() above */
+            if (self->blocksOutputBuffer->max_length >= 0 &&
+                self->blocksOutputBuffer->allocated >= self->blocksOutputBuffer->max_length) {
+                break;
+            }
             if (OutputBuffer_Grow(self->blocksOutputBuffer, out) < 0) {
                 PyErr_SetString(PyExc_ValueError, "L1586: Unknown status");
                 goto error;
@@ -1303,6 +1314,11 @@ Ppmd8Decoder_decode(Ppmd8Decoder *self,  PyObject *args, PyObject *kwargs) {
             self->in_begin = 0;
             self->in_end = 0;
         }
+        if (self->eof) {
+            self->needs_input = False;
+        } else {
+            self->needs_input = True;
+        }
     } else {
         const size_t data_size = in->size - in->pos;
         self->needs_input = False;
-- 
2.47.3