del_panel function of ncurses library causes segfault

Question

I have a code that allocates panels in one function with new_panel and tries to deallocate them with del_panel in another function. The code sample is below

void medical_cards(int regid){ //work with patient's medical cards
/*...*/
PANEL *pmedcards[cards];
WINDOW *wmedcards[cards];

bind_windows(pmedcards, wmedcards, cards); 
//this function allocates panels
/*...*/
update_panels();
doupdate();

/*...*/

i = 0;
while (i < cards)
   del_panel(pmedcards[i++]); 
  /*here I get segfault with backtrace pointing 
  to wtouchln function of the ncurses library*/
i = 0;
while (i < cards)
    delwin(wmedcards[i++]);
return;
}

void bind_windows(PANEL **pmedcards, WINDOW **wmedcards, int cards){ 
int height = 15, width = 40, ypos = LINES - 20, xpos = COLS - 45;

int i = 0;
while (i < cards) {
    wmedcards[i] = newwin(height, width, ypos, xpos + i);
    box(wmedcards[i++], 0, 0);
}
i = 0;
while (i < cards) 
    pmedcards[i] = new_panel(wmedcards[i++]);
}

The problem is that I get segfault while trying to deallocate panels, debugger points to wtouchln function as a source of trouble. It seems that no one encountered such a problem before, and man pages have scarce description of del_panel function, any help is appreciated. What I expect is that del_panel will do its job of freeing resources and return normally, without causing the program to crash.

Questions seeking debugging help ("why isn't this code working?") must include the desired behavior, a specific problem or error and the shortest code necessary to reproduce it in the question itself. Questions without a clear problem statement are not useful to other readers. See: How to create a [mcve]. — Swordfish, Feb 24 '19 at 13:33

score 0 · Accepted Answer · answered Feb 24 '19 at 13:51

0

pmedcards[i] = new_panel(wmedcards[i++]);

What is first i or i++? This is UB.

answered Feb 24 '19 at 13:51

Michał Marszałek

160
2
10

Thats funny, such a simple mistake), Thank you so much!!! – Babur Makhmudov Feb 24 '19 at 14:07

score 0 · Answer 2 · answered Feb 24 '19 at 14:11

0

The problem was not related to ncurses library, rather a silly error while allocating new panel that caused undefined behavior, as pointed out Michal Marszalek. Problem solved

answered Feb 24 '19 at 14:11

Babur Makhmudov

307
1
8

del_panel function of ncurses library causes segfault

2 Answers2