I am getting the error munmap_chunk(): invalid pointer when the program returns from the main function. I have run the debugger and I noticed that the error happens when the program return from main and jumps to the file new_allocator.h at the line ::operator delete(__p, ...
Code:
#include <iostream>
#include <vector>
#include <cmath>
// Solves the matrix equation Ax = b.
// A is a square matrix of size n x n.
// x is a vector of size n.
// b is a vector of size n.
std::vector<double> solve(std::vector<std::vector<double>>& A, std::vector<double>& b) {
int n = A.size();
for (int k = 0; k < n; k++) {
int iMax = k;
double maxVal = std::abs(A[k][k]);
for (int i = k+1; i < n; i++) {
if (std::abs(A[i][k]) > maxVal) {
iMax = i;
maxVal = std::abs(A[i][k]);
}
}
if (maxVal < 1e-10) {
throw std::runtime_error("A is not invertible");
}
std::swap(A[k], A[iMax]);
std::swap(b[k], b[iMax]);
for (int i = k+1; i < n; i++) {
double factor = A[i][k] / A[k][k];
for (int j = k+1; j < n+1; j++) {
A[i][j] -= factor * A[k][j];
}
A[i][k] = 0;
b[i] -= factor * b[k];
}
}
std::vector<double> x(n);
for (int i = n-1; i >= 0; i--) {
double sum = 0;
for (int j = i+1; j < n; j++) {
sum += A[i][j] * x[j];
}
x[i] = (b[i] - sum) / A[i][i];
}
return x;
}
int main() {
std::vector<std::vector<double>> A = {
{0.5, 0, 0, 0, 0, 0, 0, 0, -1, 0, 0},
{0, 0, 0, 0, 0, 0, -1, 0, 1, 0, 0},
{0, 0, 0.25, -0.25, 0, 0, 1, 0, 0, 0, 1},
{0, 0, -0.25, 0.25, 0, 0, 0, 0, 0, 1, 0},
{0, 0, 0, 0, 0, 0, 0, 1, 0, -1, 0},
{0, 0, 0, 0, 0, 0.125, 0, 0, 0, 0, -1},
{0, -1, 1, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0},
{-1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 0, 0, 1, -1, 0, 0, 0, 0, 0, 0},
{0, 0, 1, 0, 0, -1, 0, 0, 0, 0, 0}
};
std::vector<double> b = {0, 0, 0, 0, 0, 0, 12, 10, 0, 0, 0};
// Solve the equation Ax = b.
auto x = solve(A, b);
// Print the solution.
for (int i = 0; i < x.size(); i++) {
std::cout << x[i] << std::endl;
}
return 0;
}
The output of the program:
-2.28571
-2.28571
9.71429
10
10
9.71429
-1.14286
-0.0714286
-1.14286
-0.0714286
1.21429
munmap_chunk(): invalid pointer
I have checked similar questions on Stack Overflow but all of them allocate memory using malloc or new which is not my case. I don't allocate any dynamic memory, all the memory I use is in the stack! I know the class std::vector allocate memory but I think it is managed by the class itself and I shouldn't worry about it.
I have tried the following to fix the problem:
A.clear(); x.clear(); b.clear();None of these solutions have worked.
What is causing this issue? How can I solve it?
If you run your program under Valgrind, you'll instantly see where the problem is:
...
==2018== Invalid read of size 8
==2018== at 0x109635: solve(...) (1.cpp:28)
==2018== by 0x10A479: main (1.cpp:65)
==2018== Address 0x4db75a8 is 0 bytes after a block of size 88 alloc'd
...
==2018== Invalid write of size 8
==2018== at 0x10963E: solve(...) (1.cpp:28)
==2018== by 0x10A479: main (1.cpp:65)
==2018== Address 0x4db75a8 is 0 bytes after a block of size 88 alloc'd
...
Line 28 is:
A[i][j] -= factor * A[k][j];
Looking into the for loop termination condition, j < n + 1, the problem becomes obvious.