when use ncurses in multi-threaded , the terminal garbled [duplicate] - c

Question

This question already has an answer here:
Why has no one written a threadsafe branch of the ncurses library?
(1 answer)
Closed 5 years ago.
When I use ncurses write a library management system, terminals garbled when multi-threaded，my layout has three windows.
1.My code named ncurses.c
#include <stdio.h>
#include <ncurses.h>
#include <pthread.h>
#include <time.h>
#include <unistd.h>
typedef struct _WIN_struct {
int startx, starty;
int height, width;
} WIN;
WIN winTitle; /* title win */
WIN winMenu; /* Main menu win */
WIN winNews; /* win news */
WINDOW *create_newwin(int height, int width, int starty, int startx) {
WINDOW *local_win;
local_win = newwin(height, width, starty, startx);
box(local_win, 0, 0);
wrefresh(local_win);
return local_win;
}
char *getTimeNow() {
time_t rawtime;
struct tm *timeinfo;
time(&rawtime);
timeinfo = localtime(&rawtime);
return asctime(timeinfo);
}
void *threadfunc_title(void *p) {
WINDOW *windowTitle;
windowTitle = create_newwin(winTitle.height, winTitle.width, winTitle.starty, winTitle.startx);
/* show title and time */
for (;;) {
mvwprintw(windowTitle, winTitle.height/2, winTitle.width/2 - 10, "%s", "Library Management System");
mvwprintw(windowTitle, winTitle.height-2, winTitle.width-30, "%s", getTimeNow());
wrefresh(windowTitle);
sleep(1);
}
}
void *threadfunc_menu(void *p) {
WINDOW *windowMenu;
windowMenu = create_newwin(winMenu.height, winMenu.width, winMenu.starty, winMenu.startx);
for (;;) {
/* now do nothing */
sleep(1);
}
}
void *threadfunc_news(void *p) {
WINDOW *windowNews;
windowNews = create_newwin(winNews.height, winNews.width, winNews.starty, winNews.startx);
for (;;) {
wprintw(windowNews, "%d. %s,%s", getTimeNow(), 1, "a borrow a book from c");
wrefresh(windowNews);
wclear(windowNews);
sleep(5);
}
}
void initWin(WIN *p_win, int height, int width, int starty, int startx) {
p_win->height = height;
p_win->width = width;
p_win->starty = starty;
p_win->startx = startx;
}
int main(int argc, char *argv[])
{
pthread_t pidTitle;
pthread_t pidMenu;
pthread_t pidNews;
initscr();
start_color();
cbreak();
keypad(stdscr, TRUE);
noecho();
/* init location */
initWin(&winTitle, LINES*0.2, COLS, 0 , 0);
initWin(&winMenu, LINES*0.7, COLS*0.7, LINES*0.25, 0);
initWin(&winNews, LINES*0.7, COLS*0.2, LINES*0.25, COLS*0.7);
pthread_create(&pidTitle, NULL, threadfunc_title, NULL);
pthread_create(&pidMenu, NULL, threadfunc_menu, NULL);
pthread_create(&pidNews, NULL, threadfunc_news, NULL);
pthread_join(pidTitle, NULL);
pthread_join(pidMenu, NULL);
pthread_join(pidNews, NULL);
endwin();
return 0;
}
2.Three threads for three windows, thread_func_xxx() is pthread_create() third parameter.
3.Compile and Run
$ gcc ncurses.c -lncurses -lpthread -o ncurses
$ ./ncurses
then, I get terminal garbled.
ps:
1.I have changed -lncurses to -lncursesw, but no effect.
2.if you don not have installed ncurses, you can follow this.

Answer 1

short: the example won't work because the lower-level functions used to update the screen share data which isn't mutex'd. If you compile ncurses with the pthread option, that improves the re-entrancy of the higher-level functions and adds some mutexes, it's possible to use multiple threads.