_GLIBCXX_DEBUG を使ってみる (C++)

C++

Published: 2020-04-18

確認環境

$ g++ --version
g++ (Homebrew GCC 9.2.0) 9.2.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

調査

_GLIBCXX_DEBUG あり

test.cpp

#define _GLIBCXX_DEBUG

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> a(5);

    cout << "---1---" << endl;
    a[1] = 20;
    cout << a[1] << endl;
    cout << "---2---" << endl;
    a[10000000] = 99;
}

出力結果

---1---
20
---2---
/usr/local/Cellar/gcc/9.2.0/include/c++/9.2.0/debug/vector:427:
In function:
    std::__debug::vector<_Tp, _Allocator>::reference
    std::__debug::vector<_Tp,
    _Allocator>::operator[](std::__debug::vector<_Tp,
    _Allocator>::size_type) [with _Tp = int; _Allocator =
    std::allocator<int>; std::__debug::vector<_Tp, _Allocator>::reference =
    int&; std::__debug::vector<_Tp, _Allocator>::size_type = long unsigned
    int]

Error: attempt to subscript container with out-of-bounds index 10000000, but
container only holds 5 elements.

Objects involved in the operation:
    sequence "this" @ 0x0x7ffeebcfa610 {
      type = std::__debug::vector<int, std::allocator<int> >;
    }
Abort trap: 6

_GLIBCXX_DEBUG なし

test.cpp

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> a(5);

    cout << "---1---" << endl;
    a[1] = 20;
    cout << a[1] << endl;
    cout << "---2---" << endl;
    a[10000000] = 99;
}

出力結果

---1---
20
---2---
Segmentation fault: 11

_GLIBCXX_DEBUG ありだと、エラーの原因も記載されています。

参考

Macros