From f95968a3725309433e1dfed1ecfe1b5b32c44d74 Mon Sep 17 00:00:00 2001
From: krrish175-byte <krrishbiswas175@gmail.com>
Date: Thu, 26 Feb 2026 23:56:38 +0530
Subject: [PATCH] gpl: fix segfault when selecting instance in debug mode

Fix three issues that caused segmentation faults in GPL debug mode:

1. In debugForNesterovPlace(), the nbVec_ search for the selected
   instance was outside the 'if (inst)' guard, causing
   cell_handle->contains(nullptr) to be called when no debug instance
   was specified.

2. In drawNesterov(), accessing nbVec_[nb_index] for gradient drawing
   without checking that nb_index is within bounds of nbVec_.

3. In reportSelected(), same missing bounds check on nbVec_[nb_index].

Fixes #9017

Signed-off-by: Krrish Biswas <krrish175byte@gmail.com>
Signed-off-by: krrish175-byte <krrishbiswas175@gmail.com>
---
 src/gpl/src/graphicsImpl.cpp | 60 ++++++++++++++++++++++++------------
 1 file changed, 41 insertions(+), 19 deletions(-)

diff --git a/src/gpl/src/graphicsImpl.cpp b/src/gpl/src/graphicsImpl.cpp
index 6bd04b3ca1..79b9b90c9f 100644
--- a/src/gpl/src/graphicsImpl.cpp
+++ b/src/gpl/src/graphicsImpl.cpp
@@ -27,6 +27,30 @@
 
 namespace gpl {
 
+namespace {
+
+std::optional<size_t> getSelectedNesterovBaseIndex(
+    size_t nb_selected_index,
+    const std::vector<std::shared_ptr<NesterovBase>>& nbVec,
+    utl::Logger* logger,
+    int msg_id)
+{
+  size_t nb_index = 0;
+  if (nb_selected_index != std::numeric_limits<size_t>::max()) {
+    nb_index = nb_selected_index;
+  } else if (!nbVec.empty()) {
+    logger->warn(
+        utl::GPL, msg_id, "Selected instance not found in any NesterovBase");
+  }
+
+  if (nb_index >= nbVec.size()) {
+    return std::nullopt;
+  }
+  return nb_index;
+}
+
+}  // namespace
+
 GraphicsImpl::GraphicsImpl(utl::Logger* logger)
     : HeatMapDataSource(logger, "gpl", "gpl"), logger_(logger), mode_(Mbff)
 {
@@ -119,14 +143,14 @@ void GraphicsImpl::debugForNesterovPlace(
         break;
       }
     }
-  }
 
-  for (const auto& nb : nbVec_) {
-    for (size_t idx = 0; idx < nb->getGCells().size(); ++idx) {
-      GCellHandle cell_handle = nb->getGCells()[idx];
-      if (cell_handle->contains(inst)) {
-        nb_selected_index_ = &nb - nbVec_.data();
-        break;
+    for (const auto& nb : nbVec_) {
+      for (size_t idx = 0; idx < nb->getGCells().size(); ++idx) {
+        GCellHandle cell_handle = nb->getGCells()[idx];
+        if (cell_handle->contains(inst)) {
+          nb_selected_index_ = &nb - nbVec_.data();
+          break;
+        }
       }
     }
   }
@@ -393,13 +417,12 @@ void GraphicsImpl::drawNesterov(gui::Painter& painter)
     const GCell* gcell = nbc_->getGCellByIndex(selected_);
     auto wlCoeffX = np_->getWireLengthCoefX();
     auto wlCoeffY = np_->getWireLengthCoefY();
-    size_t nb_index = 0;
-    if (nb_selected_index_ != kInvalidIndex) {
-      nb_index = nb_selected_index_;
-    } else {
-      logger_->warn(
-          utl::GPL, 317, "Selected instance not found in any NesterovBase");
+    auto opt_nb_index = getSelectedNesterovBaseIndex(
+        nb_selected_index_, nbVec_, logger_, 317);
+    if (!opt_nb_index) {
+      return;
     }
+    size_t nb_index = *opt_nb_index;
     FloatPoint densityGrad = nbVec_[nb_index]->getDensityGradient(gcell);
     FloatPoint wlGrad
         = nbc_->getWireLengthGradientWA(gcell, wlCoeffX, wlCoeffY);
@@ -524,13 +547,12 @@ void GraphicsImpl::reportSelected()
         = nbc_->getWireLengthGradientWA(gcell, wlCoeffX, wlCoeffY);
     logger_->report("  sum wl  ({: .2e}, {: .2e})", wlGrad.x, wlGrad.y);
 
-    size_t nb_index = 0;
-    if (nb_selected_index_ != kInvalidIndex) {
-      nb_index = nb_selected_index_;
-    } else {
-      logger_->warn(
-          utl::GPL, 318, "Selected instance not found in any NesterovBase");
+    auto opt_nb_index = getSelectedNesterovBaseIndex(
+        nb_selected_index_, nbVec_, logger_, 318);
+    if (!opt_nb_index) {
+      return;
     }
+    size_t nb_index = *opt_nb_index;
     FloatPoint densityGrad = nbVec_[nb_index]->getDensityGradient(gcell);
     float densityPenalty = nbVec_[nb_index]->getDensityPenalty();
     logger_->report("  density ({: .2e}, {: .2e}) (penalty: {})",