C++: debug OK ,run release get wrong answer

Question

I have extracted the code which get problem The following code define an 2D array with vector. and then print the 2D array. When I use debug mode to run it, it print the right answer, But when I run it without debug(ie. the release mode). sometimes it print the whole 2D array, sometimes it print part of it, and then just exit without any message. why this happened? Thank you!.

running environment:
Windows 10 version: 10.0.16299.125
Clion 2017.3
Mingw64 5.0

Clion's CmakeLists.txt:
cmake_minimum_required(VERSION 3.8)
project(Test)
set(CMAKE_CXX_STANDARD 11)
set(SOURCE_FILES main.cpp)
add_executable(Test ${SOURCE_FILES})

#include <vector>
#include <iostream>

using namespace std;

int main()
{
    vector<vector<int>> graph{{0, 4,  0, 0,  0,  0,  0, 8,  0},
                              {4, 0,  8, 0,  0,  0,  0, 11, 0},
                              {0, 8,  0, 7,  0,  4,  0, 0,  2},
                              {0, 0,  7, 0,  9,  14, 0, 0,  0},
                              {0, 0,  0, 9,  0,  10, 0, 0,  0},
                              {0, 0,  4, 14, 10, 0,  2, 0,  0},
                              {0, 0,  0, 0,  0,  2,  0, 1,  6},
                              {8, 11, 0, 0,  0,  0,  1, 0,  7},
                              {0, 0,  2, 0,  0,  0,  6, 7,  0}};


    for(int i = 0; i < graph.size(); i++)
    {
        for(int j = 0; j < graph[i].size(); j++)
        {
            cout  << i << "-" << j  << ": "<< graph[i][j] << endl;
        }
        cout << endl;
    }
    return 0;
}

the output is not stable, sometime succeed, sometime failed, following is two of the wrong outputs The first wrong output:

E:\coding\LCCPP\Test\cmake-build-debug\Test.exe
0-0: 0
0-1: 4
0-2: 0
0-3: 0
0-4: 0
0-5: 0
0-6: 0
0-7: 8
0-8: 0

1-0: 4
1-1

1-1:
Process finished with exit code 0

The second wrong output:

E:\coding\LCCPP\Test\cmake-build-debug\Test.exe
0-0: 0
0-1: 4
0-2: 0
0-3: 0
0-4: 0
0-5: 0
0-6: 0
0-7: 8
0-8: 0

1-0: 4
1-1: 0
1-2: 8
1-3: 0
1-4: 0
1-5: 0
1-6: 0
1-7: 11
1-8: 0

2-0: 0
2-1: 8
2-2: 0
2-3: 7
2-4: 0
2-5: 4
2-6: 0
2-7: 0
2-8: 2

3-0: 0
3-1: 0
3-2: 7
3-3: 0
3-4: 9
3-5: 14
3-6: 0
3-7: 0
3-8: 0

4-0: 0
4-1: 0
4-2: 0
4-3: 9
4-4: 0
4-5: 10
4-6: 0
4-7: 0
4-8: 0

5-0: 0
5-1: 0
5-2: 4
5-3: 14
5-4: 10
5-5: 0
5-6: 2
5-7: 0
5-8: 0

6-0: 0
6-1: 0
6-2: 0
6-3: 0
6-4: 0
6-5: 2
6-6: 0
6-7: 1
6-8: 6

7-0: 8
7-1: 11
7-2: 0
7-3: 0
7-4: 0
7-5: 0
7-6: 1
7-7: 0
7-8: 7

8-0: 0
8-1: 0
8-2: 2
8-3: 0
8-4: 0
8-5: 0
8
Process finished with exit code 0

The right output:

E:\coding\LCCPP\Test\cmake-build-debug\Test.exe
0-0: 0
0-1: 4
0-2: 0
0-3: 0
0-4: 0
0-5: 0
0-6: 0
0-7: 8
0-8: 0

1-0: 4
1-1: 0
1-2: 8
1-3: 0
1-4: 0
1-5: 0
1-6: 0
1-7: 11
1-8: 0

2-0: 0
2-1: 8
2-2: 0
2-3: 7
2-4: 0
2-5: 4
2-6: 0
2-7: 0
2-8: 2

3-0: 0
3-1: 0
3-2: 7
3-3: 0
3-4: 9
3-5: 14
3-6: 0
3-7: 0
3-8: 0

4-0: 0
4-1: 0
4-2: 0
4-3: 9
4-4: 0
4-5: 10
4-6: 0
4-7: 0
4-8: 0

5-0: 0
5-1: 0
5-2: 4
5-3: 14
5-4: 10
5-5: 0
5-6: 2
5-7: 0
5-8: 0

6-0: 0
6-1: 0
6-2: 0
6-3: 0
6-4: 0
6-5: 2
6-6: 0
6-7: 1
6-8: 6

7-0: 8
7-1: 11
7-2: 0
7-3: 0
7-4: 0
7-5: 0
7-6: 1
7-7: 0
7-8: 7

8-0: 0
8-1: 0
8-2: 2
8-3: 0
8-4: 0
8-5: 0
8-6: 6
8-7: 7
8-8: 0


Process finished with exit code 0

I think there is no problem with this code, although it's better to use size_t instead of int. Show all code / another part of code. — moskalenco_a
I am not able to find an error in your code. Nevertheless, I compiled it on RetHat 6 with gcc, clang and the intel compiler. I changed the optimisation level. In all cases debug and release have the very same output. — schorsch312

Swift - Friday Pie Swift - Friday Pie · Accepted Answer · 2018-01-18T06:42:15

There is no actual problems with code, it is likely issue of IDE not providing output. Essentially your program exits before whole pipe buffer was printed in console. Pipe is closed without any error when child process exits, and parent process have nothing to print. What happens if you pause program at end?

While it is not good to not provide "return" in non-void function, mingw adds equivalent of return 0; to main()...

PS: Consider usage of range-fors:

int main()   
{
    using namespace std;
    vector<vector<int>> graph{{0, 4,  0, 0,  0,  0,  0, 8,  0},
                              {4, 0,  8, 0,  0,  0,  0, 11, 0},
                              {0, 8,  0, 7,  0,  4,  0, 0,  2},
                              {0, 0,  7, 0,  9,  14, 0, 0,  0},
                              {0, 0,  0, 9,  0,  10, 0, 0,  0},
                              {0, 0,  4, 14, 10, 0,  2, 0,  0},
                              {0, 0,  0, 0,  0,  2,  0, 1,  6},
                              {8, 11, 0, 0,  0,  0,  1, 0,  7},
                              {0, 0,  2, 0,  0,  0,  6, 7,  0}};


    for(auto &line: graph)
    {
        int i = 0, j= 0;
        for(auto v : line )
        {
            cout  << i << "-" << j  << ": "<< v << endl;
            j++;
        }
        i++;
        cout << endl;
    }
    return 0;
}

( http://en.cppreference.com/w/cpp/language/range-for )

C++: debug OK ,run release get wrong answer

2 Answers