Segmentation fault while calling getch()

Question

I am trying to make a simple console program using curses on ubuntu, but each time I try to call getch and make it wait for input, when I input the input, it throws a segmentation fault. I did initialize the library using the initscr() function in another part of my code.

Here is the part of code throwing the segmentation fault :

int ch;
ch = getch();

Any help is greatly appreciated,

Mindoo

EDIT: After switching out the int for a char, I get the following warnings that revolve arround this piece of code right after the previously mentioned getch().

char ch;
  ch = getch();

  //Get xObject position
  int xObjectX = getXObject()->getPosX();
  int xObjectY = getXObject()->getPosY();

  switch (ch) {
    case KEY_LEFT:
      getXObject()->move(xObjectY, xObjectX--);
      break;

    case KEY_RIGHT:
      getXObject()->move(xObjectY, xObjectX++);
      break;

    case KEY_UP:
      getXObject()->move(xObjectY++, xObjectX);
      break;

    case KEY_DOWN:
      getXObject()->move(xObjectY--, xObjectX);
      break;

    case KEY_BACKSPACE:
      game->stop();
      break;

I get these warnings :

TestGameState.cpp: In member function ‘virtual void TestGameState::handleInput()’:
TestGameState.cpp:21:5: warning: case label value exceeds maximum value for type
     case KEY_LEFT:
     ^
TestGameState.cpp:25:5: warning: case label value exceeds maximum value for type
     case KEY_RIGHT:
     ^
TestGameState.cpp:29:5: warning: case label value exceeds maximum value for type
     case KEY_UP:
     ^
TestGameState.cpp:33:5: warning: case label value exceeds maximum value for type
     case KEY_DOWN:
     ^
TestGameState.cpp:37:5: warning: case label value exceeds maximum value for type
     case KEY_BACKSPACE:

That is obviously not enough to go on. post a complete example. — Anon Mail, Mar 14 '17 at 20:30
Well, what else do you want me to post, thats pretty much everything I can post without posting my whole project folder. — mindoo, Mar 14 '17 at 20:32
This part of the code is __definitely not__ causing a segmentation fault. — BusyProgrammer, Mar 14 '17 at 20:33
Thats what I thought, but if I put a printw() before and after this part, the second one does not appear as the segfault appears first where as the first does appear on screen. — mindoo, Mar 14 '17 at 20:35
Actually it could be, @ABusyProgrammer, but it would be the result of bad Juju a lot earlier. For example, a crash over `ch = getch();` could be the visible manifestation of an eariler stack overflow. Either way, all we can do with what's been provided is guess. — user4581301, Mar 14 '17 at 20:35
Guess #1: Did you correctly defrobble the Bugornic Atimeter? — user4581301, Mar 14 '17 at 20:37
@ABusyProgrammer I tried switching out the int for a char, and it got rid of the seg fault, but it spit out a lot of warnings. — mindoo, Mar 14 '17 at 20:39
@ABusyProgrammer `int ch;` is the correct line, `char ch;` is wrong. — n. m. could be an AI, Mar 14 '17 at 20:48
May I ask, what is KEY_UP, and all the other variables causing the error? I have frankly never done game development in C++, so I cannot comment on the warnings — BusyProgrammer, Mar 14 '17 at 20:50
@ABusyProgrammer there are hundreds of questions on this site that deal with this exact blunder. `getch()` returns an `int`. Read the documentation. — n. m. could be an AI, Mar 14 '17 at 20:53
@ABusyProgrammer KEY_UP and all the others are constants defined by curses that represent the arrow keys etc... — mindoo, Mar 14 '17 at 20:56
@ABusyProgrammer sorry we're talking about `getch()` not `getchar()`, my bad. `getch()` doesn't have hundreds of questions on this site. But it still returns an `int` just like `getchar()`, the same arguments ap[ply. — n. m. could be an AI, Mar 14 '17 at 20:57
"if I put a printw() before and after this part" It's not a guaranteed way to locate the problem. Use a proper debugger. Also go back to `int ch`. — n. m. could be an AI, Mar 14 '17 at 21:02
@n.m. I see. Well in that case, some other part of the code has to be causing the error. — BusyProgrammer, Mar 14 '17 at 21:36
@mindoo Use a debugger, it will help you more than using printf statements. — BusyProgrammer, Mar 14 '17 at 21:37

score 0 · Answer 1 · answered Mar 14 '17 at 20:46

0

That function is unlikely to be the cause. How did you tell that line cause SF?

You may try: 1. use getchar instead 2. try not to use curses

answered Mar 14 '17 at 20:46

Marcus Sun

21
2

I need curse to do the displaying. I realized that was the line causing the segfault by putting a printw("example") line on each end of that piece of code and it only displayed once. – mindoo Mar 14 '17 at 20:48
Try to isolate problems. Like remove anything, just this like to see if crash still happen. Then add piece by piece. Most likely, something instead of this caused the crash. – Marcus Sun Mar 14 '17 at 20:52
What do you mean, thats just what I did – mindoo Mar 14 '17 at 20:53
Tryo to use a debugger, printing message is not a reliable way to find out the exact fault point. – Marcus Sun Mar 14 '17 at 20:55

Segmentation fault while calling getch()

1 Answers1