Why AddressSanitizer:DEADLYSIGNAL? - c++

Question

class Solution {
int maxRow, maxCol;
int x[4] = {1, -1, 0, 0};
int y[4] = {0, 0, 1, -1};
bool isValid(int row, int col){
return (row >= 0 && row < maxRow && col >= 0 && col < maxCol);
}
int longestPath(int row, int col, vector<vector<int>>& matrix, vector<vector<int>>& dp){
if(dp[row][col] != -1){
return dp[row][col];
}
int longestCurrPath = 1;
for(int dir = 0; dir < 4; ++dir){
int newRow = row + x[dir];
int newCol = col + y[dir];
if(isValid(newRow, newCol) && matrix[col][row] > matrix[newRow][newCol]){
longestCurrPath = max(longestCurrPath, longestPath(newRow, newCol, matrix, dp) + 1);
}
}
return dp[row][col] = longestCurrPath;
}
public:
int longestIncreasingPath(vector<vector<int>>& matrix) {
maxRow = matrix.size();
maxCol = matrix[0].size();
int LIP = 1;
vector<vector<int>> dp(maxRow + 1, vector<int>(maxCol + 1, -1));
for(int row = 0; row < maxRow; ++row){
for(int col = 0; col < maxCol; ++col){
if(dp[row][col] == -1)
LIP = max(LIP, longestPath(row, col, matrix, dp));
}
}
return LIP;
}
};
AddressSanitizer:DEADLYSIGNAL
==31==ERROR: AddressSanitizer: stack-overflow on address 0x7ffe60cafff8 (pc 0x0000003466d2 bp 0x7ffe60cb0070 sp 0x7ffe60cb0000 T0)
==31==ABORTING

Answer 1

Answer: Stackoverflow.
Your recursive logic is buggy. And you perpetually end up in a situation like this:
See comments in the code below
int longestPath(int row, int col, vector<vector<int>>& matrix, vector<vector<int>>& dp){
if(dp[row][col] != -1){
// Termination depends on `dp`
return dp[row][col];
}
int longestCurrPath = 1;
for(int dir = 0; dir < 4; ++dir){
int newRow = row + x[dir];
int newCol = col + y[dir];
if(isValid(newRow, newCol) && matrix[col][row] > matrix[newRow][newCol]) {
// Making recursive calls without ever influencing `dp`
longestCurrPath = max(longestCurrPath, longestPath(newRow, newCol, matrix, dp) + 1);
}
}
// This is the only time you change `dp`
return dp[row][col] = longestCurrPath;
}