'Matrix Multiplication causes UndefinedBehaviorSanitizer:DeadlySignal Error

In trying to solve this kata on codewars (TL;DR implement matrix multiplication).

I've come up with this solution:

#include <stdexcept>
#include <iostream>

using std::vector;

static inline long long _determinant(vector<vector<long long>> const& m, vector<std::size_t> const& is, vector<std::size_t> const& js);

long long determinant(vector< vector<long long> > m) {
  for( vector<long long> i : m ) {
    std::cout << "(";
    bool first = true;
    for (long long j : i) {
      if(!first) {
        std::cout << ',';
      }
      std::cout << j;
      first = false;
    }
    std::cout << ")\n";
  }
  std::cout << "\n";

  if (m.empty())
    throw std::domain_error("A determinant cannot be calculated on an empty matrix.");
  if (m.size() != m[0].size())
    throw std::domain_error("A determinant is only defined for a square matrix.");
  if (m.size() == 1)
    return m[0][0];

  std::vector<std::size_t> include_idx(m.size());
  std::generate(include_idx.begin(), include_idx.end(), [] {
    static int i = 0;
    return i++;
  });

  return _determinant(m, include_idx, include_idx);
//   return 0;
}

static inline long long _determinant(vector<vector<long long>> const& m, vector<std::size_t> const& is, vector<std::size_t> const& js) {
  size_t end = is.size();
  if(end == 2)
    return m[is[0]][js[0]] * m[is[1]][js[1]] - m[is[1]][js[0]] * m[is[0]][js[1]];

  long long determinant = 0;
  short sign = 1;
  vector<std::size_t> new_is = is;
  new_is.erase(new_is.begin());
  for( size_t j = 0; j < js.size(); j++) {
      vector<std::size_t> new_js = js;
      new_js.erase(new_js.begin() + j);
      determinant += sign * (m[0][js[j]]) * (_determinant(m, new_is, new_js));;
      sign *= -1;
  }

  return determinant;
};

The tests provided with the kata are:

using std::vector;
using testing::Eq;

TEST(libhelloTest, determinantTest) {
  EXPECT_THAT(determinant(vector<std::vector<long long> >{
                  vector<long long>{1}}),
                  Eq(1));
  
  EXPECT_THAT(determinant(vector<std::vector<long long> >{
                  vector<long long>{1, 3},
                  vector<long long>{2, 5},
              }),
              Eq(-1));
  
  EXPECT_THAT(determinant(vector< std::vector<long long> > {
              vector<long long> {2,  5,  3},
              vector<long long> {1, -2, -1},
              vector<long long> {1,  3,  4}
              }),
              Eq(-20));
}

These run absolutely fine locally, but when I put it into codewars I get:

UndefinedBehaviorSanitizer:DEADLYSIGNAL
==1==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address 0x000000000024 (pc 0x000000425ae0 bp 0x7ffc425bf610 sp 0x7ffc425bf550 T1)
==1==The signal is caused by a READ memory access.
==1==Hint: address points to the zero page.
==1==WARNING: invalid path to external symbolizer!
==1==WARNING: Failed to use and restart external symbolizer!
    #0 0x425adf  (/workspace/test+0x425adf)
    #1 0x425d02  (/workspace/test+0x425d02)
    #2 0x4259c5  (/workspace/test+0x4259c5)
    #3 0x428b61  (/workspace/test+0x428b61)
    #4 0x426fbe  (/workspace/test+0x426fbe)
    #5 0x426b3f  (/workspace/test+0x426b3f)
    #6 0x42679b  (/workspace/test+0x42679b)
    #7 0x42b7c5  (/workspace/test+0x42b7c5)
    #8 0x425e6d  (/workspace/test+0x425e6d)
    #9 0x7f8772499bf6  (/lib/x86_64-linux-gnu/libc.so.6+0x21bf6)
    #10 0x4046b9  (/workspace/test+0x4046b9)

UndefinedBehaviorSanitizer can not provide additional info.
==1==ABORTING

I've tried compiling and linking with -fsanitize=undefined (I'm using clang++ 14.0.1) but that doesn't replicate the issue. Does anyone know, firstly how I can replicate this error, and secondly what is up with my code?

c++undefined-behavior


Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source

Related Questions