From ccdcf03fa84c9eb2fc5ac0ee4d197a0fe19cb20a Mon Sep 17 00:00:00 2001
From: Codex instance <matt+codex@gretton-dann.org.uk>
Date: Thu, 30 Jul 2026 16:49:21 +0100
Subject: [PATCH 1/2] test: cover completed solver boards

Exercise both the trivial order-1 solution and the feasible order-8 solution through the independent placement validator.

With the existing completion ordering, the focused test reports a heap-buffer-overflow under AddressSanitizer before validation can run.

Refs: #14
---
 CMakeLists.txt |  1 +
 tests/tests.cc | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 56c52d0..a87e234 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,4 +15,5 @@ if(BUILD_TESTING)
   add_test(NAME construction COMMAND partridge_tests construction)
   add_test(NAME rendering COMMAND partridge_tests rendering)
   add_test(NAME solver-small COMMAND partridge_tests solver-small)
+  add_test(NAME solver-completion COMMAND partridge_tests solver-completion)
 endif()
diff --git a/tests/tests.cc b/tests/tests.cc
index e022ecc..939fc78 100644
--- a/tests/tests.cc
+++ b/tests/tests.cc
@@ -280,6 +280,19 @@ namespace {
         "result adapter did not convert encoded placement coordinates");
     return failures;
   }
+
+  auto test_solver_completion() -> int {
+    int failures = 0;
+    for (auto const order: std::array<std::uint64_t, 2>{1, 8}) {
+      auto const solution = find_solution(order);
+      auto const validation = validate(order, solution);
+      failures += expect(
+          validation.valid(),
+          "solver returned an invalid order-" + std::to_string(order) +
+              " solution:\n" + validation.text());
+    }
+    return failures;
+  }
 }
 
 int main(int argc, char **argv) {
@@ -301,6 +314,9 @@ int main(int argc, char **argv) {
   if (test == "solver-small") {
     return test_small_solver();
   }
+  if (test == "solver-completion") {
+    return test_solver_completion();
+  }
   std::cerr << "unknown test: " << test << '\n';
   return 2;
 }
-- 
2.54.0


From ce39d0a4d051d14071ef658c8d5cd86a8eb8b22f Mon Sep 17 00:00:00 2001
From: Codex instance <matt+codex@gretton-dann.org.uk>
Date: Thu, 30 Jul 2026 16:50:19 +0100
Subject: [PATCH 2/2] solver: check completion before probing square

next_pos() returns the grid end sentinel when a placement completes the board. Avoid passing that sentinel to largest_square(), which requires an in-range position and otherwise reads past the grid.

Tests: Debug, Release, ASan, and UBSan CTest suites

Refs: #14
---
 main.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/main.cc b/main.cc
index c71cae1..55e69f0 100644
--- a/main.cc
+++ b/main.cc
@@ -297,10 +297,11 @@ namespace {
       sqs.push_back(sq);
 
       pos = grid.next_pos(pos + idx);
-      idx = grid.largest_square(pos, n);
 
       // Have we reached the end?  If so success!
       if (pos == grid.end()) { break; }
+
+      idx = grid.largest_square(pos, n);
     }
 
     return {length, sqs};
-- 
2.54.0