schmidt%blanche.ics.uci.edu@ORION.CF.UCI.EDU ("Douglas C. Schmidt") (11/27/88)
Hi,
The following program displays very strange behavior... It appears
that a constant magically changes its value inside a loop. When the
const qualifier is removed the program runs correctly. When linked
with the -lcurses and -ltermcap libraries, the output of this program
should print a title followed by 7 double spaced menu options.
However, g++ ( both with and without -O, on the sun 3 and sun 4 )
produces the first 3 options double spaced, and the remainder single
spaced. If one examines the source code it is obvious that this only
could happen if the constant is changing its value inside the for
loop! CC 1.2.1 gets it correct, as does g++ if the line:
const int SPACING = (((option_num*2 + option_row) < 22 )? 2 : 1 );
is changed to
int SPACING = (((option_num*2 + option_row) < 22 )? 2 : 1 );
Doug
----------------------------------------
typedef unsigned short chtype;
struct _win_st {
short _cury, _curx;
short _maxy, _maxx;
short _begy, _begx;
short _flags;
chtype _attrs;
char _clear;
char _leave;
char _scroll;
char _use_idl;
char _use_keypad;
char _use_meta;
char _nodelay;
chtype **_y;
short *_firstch;
short *_lastch;
short _tmarg,_bmarg;
};
typedef struct _win_st WINDOW;
extern WINDOW *stdscr, *curscr;
void Display( char *option[],
char *title,
int option_num ) {
const int TITLE_ROW = 1;
const int TITLE_COL = 36 - ( strlen( title )/2 );
initscr();
wclear(stdscr) ;
wmove(stdscr, TITLE_ROW, TITLE_COL ) ;
printw( "*** %s ***", title );
int option_col = 40 - strlen(option[0]) / 2;
int option_row = 3;
// remove the following const and the program works correctly
const int SPACING = (((option_num*2 + option_row) < 22 )? 2 : 1 );
if( option_col > TITLE_COL ) {
option_col = TITLE_COL;
}
for( int i = 0; i < option_num; i++ ) {
wmove(stdscr, option_row, option_col ) ;
printw( "%d. %s %d %d\n", i+1, option[i], option_row, SPACING );
option_row += SPACING;
}
wrefresh(stdscr) ;
endwin();
}
char *option[] = {"Maximum", "Minimum", "Mean", "Median", "Total",
"Get All Value", "Quit"};
main()
{
char *title = "STATISTIC MENU";
Display( option, title, sizeof ( option ) / sizeof ( *option ) );
}