KDevelop 4 C++ debugging shows no output for cout

halfgaar · 2010-07-13 22:14:09

Hi,

In KDevelop4, I have this C++ test program:

#include <iostream>
#include <cstdlib>

using namespace std;

int multiply(int a, int b);

int main(int argc, char **argv) {
    cout << "Helloasdf, world! abla" << endl;
    cout << "line 2" << endl;
    cout << "a line without endl";
    cout << "multiply: " << multiply(4, 10);
    return 0;
}

int multiply(int a, int b) {
    int antwoord = a * b;    
    return antwoord;    
}

When launching, it says this:

Helloasdf, world! abla
line 2
a line without endlmultiply: 40

However, when launching in debug mode, it says this:

Helloasdf, world! abla
line 2

When I add a endl to line 2, it does output the next line. When I set breakpoints, stepping over the lines doesn't do anything.

Is this a bug?

PirateJonno · 2010-07-13 23:17:18

halfgaar wrote:

Is this a bug?

Probably not. Using endl flushes the stdout buffer, and presumably optimisation stops it being flushed automatically when your program exits. If you really don't want a newline at the end, just call cout.flush()

Last edited by PirateJonno (2010-07-13 23:20:23)

halfgaar · 2010-07-14 07:52:49

When I change the code to this:

#include <iostream>
#include <cstdlib>

using namespace std;

int multiply(int a, int b);

int main(int argc, char **argv) {
    cout << "aHelloasdf, world! abla" << endl;
    cout << "line 2" << endl;
    cout << "a line without endl"; // it doesn't print this line in debug mode when there is no endl
    cout.flush();
    cout << "multiply: " << multiply(4, 10);
    cout.flush();
    return 0;
}

int multiply(int a, int b) {
    int antwoord = a * b;    
    return antwoord;    
}

It still doesn't output the last lines when debugging.

tavianator · 2010-07-14 14:33:39

Streams are automatically flushed when a program terminates, so the cout.flush() don't change anything.

I'm guessing that KDevelop expects the program to end with a newline, otherwise it will overwrite the last line. This is a reasonable expectation -- some shells do this too. So, just end your program with a newline, unless it has to output data in a really structured format for some reason.

PirateJonno · 2010-07-14 15:35:49

Don't know how I managed to misinterpret "debug mode" as "optimisation", not that it makes me any less wrong
Anyway taviantor's suggestion sounds reasonable

halfgaar · 2010-07-14 18:36:14

I'm guessing that KDevelop expects the program to end with a newline, otherwise it will overwrite the last line. This is a reasonable expectation -- some shells do this too. So, just end your program with a newline, unless it has to output data in a really structured format for some reason.

It doesn't overwrite, it just stops outputting.

But OK, I guess I can live with it if it's just the way KDevelop interprets shell output commands.

Arch Linux

#1 2010-07-13 22:14:09

KDevelop 4 C++ debugging shows no output for cout

#2 2010-07-13 23:17:18

Re: KDevelop 4 C++ debugging shows no output for cout

#3 2010-07-14 07:52:49

Re: KDevelop 4 C++ debugging shows no output for cout

#4 2010-07-14 14:33:39

Re: KDevelop 4 C++ debugging shows no output for cout

#5 2010-07-14 15:35:49

Re: KDevelop 4 C++ debugging shows no output for cout

#6 2010-07-14 18:36:14

Re: KDevelop 4 C++ debugging shows no output for cout

Board footer