agv-control-slam/docs/fixes/BUG_FIXES_SUMMARY.md

AGV Path Tracking GUI - Bug Fixes Summary

Issues Found and Fixed

1. CSV Parsing Bug (path_curve_custom.cpp)

Issue: Incorrect error handling in CSV token parsing

• Location: src/path_curve_custom.cpp, lines 35-42 (original)
• Problem: When std::stod() throws an exception for a token, the code uses continue inside the token-reading loop. This causes the offending token to be skipped while remaining tokens are still processed, resulting in misaligned column data.
• Example: CSV line "1.5, invalid, 3.0, 4.0" would be parsed as [1.5, 3.0, 4.0] instead of being rejected entirely.
• Fix:
  • Added parse_error flag to track errors
  • When any token fails to parse, skip the entire line
  • Added token trimming to handle whitespace properly
  • Improved error handling with explicit break instead of continue

2. Stanley Algorithm Index Bounds Check (control_generator.cpp)

Issue: Missing validation of findNearestPoint() return value

• Location: src/control_generator.cpp, line 87 (original)
• Problem: findNearestPoint() returns -1 when path is empty, but the code directly accesses path_points[-1] without checking, causing a crash/undefined behavior
• Crash Trace:

  int nearest_idx = path.findNearestPoint(...);
  PathPoint nearest_point = path_points[nearest_idx];  // CRASH if nearest_idx == -1
  

• Fix: Added validation to check if nearest_idx < 0 and default to index 0

3. Pure Pursuit Lookahead Point Type Conversion Bug (control_generator.cpp)

Issue: Implicit unsafe conversion of signed to unsigned integer

• Location: src/control_generator.cpp, line 188 (original)
• Problem: Converting int nearest_idx to size_t i in for loop. If nearest_idx is -1, it converts to a very large positive number (e.g., 18446744073709551615 on 64-bit systems)
• Fix:
  • Added validation to check nearest_idx < 0
  • Use explicit static_cast<size_t>() for safe conversion
  • Return safe default (first path point) if index is invalid

4. Visualization Division by Zero (qt_gui_demo.cpp)

Issue: Missing bounds check for scale calculation

• Location: examples/qt_gui_demo.cpp, line 100 (original)
• Problem: If all path points have identical coordinates, range becomes 0, causing division by zero:

  double scale = std::min(width() - 2 * padding, height() - 2 * padding) / range;
  

• Fix: Added check for range < 1e-6 and default to 1.0 to prevent division by zero

Testing Recommendations

1. Test CSV Loading with smooth_path_arc.csv:

   • Verify that the GUI no longer crashes when loading the file
   • Check that all 150 path points are loaded correctly
   • Verify visualization displays the arc path properly

2. Test Edge Cases:

   • CSV files with malformed data (missing columns, invalid numbers)
   • Paths with degenerate cases (all points at same location)
   • Empty path files
   • CSV files with extra whitespace around values

3. Verify Control Generation:

   • Run Pure Pursuit algorithm with loaded path
   • Run Stanley algorithm with loaded path
   • Check that control sequences are generated without crashes

Files Modified

1. src/path_curve_custom.cpp - CSV parsing improvements
2. src/control_generator.cpp - Index validation in Stanley and Pure Pursuit algorithms
3. examples/qt_gui_demo.cpp - Division by zero prevention in visualization

Related Issues Prevented

• Stack overflow: From invalid array access with large negative indices cast to unsigned
• Data corruption: From misaligned CSV column parsing
• Graphics rendering failures: From NaN/infinity scale values
• Segmentation faults: From accessing out-of-bounds array indices