I've convinced myself that this memory corruption bug was introduce in
Cairo 10.x and later, not the lua wrapper. This C program hits it too.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
typedef struct _cairo_linuxfb_device {
int fb_fd;
char *fb_data;
long fb_screensize;
struct fb_var_screeninfo fb_vinfo;
struct fb_fix_screeninfo fb_finfo;
} cairo_linuxfb_device_t;
static
void cairo_linuxfb_surface_destroy(void *device)
{
cairo_linuxfb_device_t *dev = (cairo_linuxfb_device_t *)device;
if (dev == NULL) {
return;
}
munmap(dev->fb_data, dev->fb_screensize);
close(dev->fb_fd);
free(dev);
}
cairo_surface_t *cairo_linuxfb_surface_create(const char *fb_name)
{
cairo_linuxfb_device_t *device;
cairo_surface_t *surface;
if (fb_name == NULL) {
fb_name = "/dev/fb0";
}
device = malloc(sizeof(*device));
// Open the file for reading and writing
device->fb_fd = open(fb_name, O_RDWR);
if (device->fb_fd == -1) {
perror("Error: cannot open framebuffer device");
exit(1);
}
// Get variable screen information
if (ioctl(device->fb_fd, FBIOGET_VSCREENINFO,
&device->fb_vinfo) == -1) {
perror("Error reading variable information");
exit(3);
}
// Figure out the size of the screen in bytes
device->fb_screensize = device->fb_vinfo.xres * device->fb_vinfo.yres
* device->fb_vinfo.bits_per_pixel / 8;
// Map the device to memory
device->fb_data = (char *)mmap(0, device->fb_screensize,
PROT_READ | PROT_WRITE, MAP_SHARED,
device->fb_fd, 0);
if ((int)device->fb_data == -1) {
perror("Error: failed to map framebuffer device to memory");
exit(4);
}
// Get fixed screen information
if (ioctl(device->fb_fd, FBIOGET_FSCREENINFO,
&device->fb_finfo) == -1) {
perror("Error reading fixed information");
exit(2);
}
surface = cairo_image_surface_create_for_data(device->fb_data,
CAIRO_FORMAT_RGB16_565,
device->fb_vinfo.xres,
device->fb_vinfo.yres,
cairo_format_stride_for_width(CAIRO_FORMAT_RGB16_565,
device->fb_vinfo.xres));
cairo_surface_set_user_data(surface, NULL, device,
&cairo_linuxfb_surface_destroy);
return surface;
}
int main (int argc, char *argv[])
{
cairo_surface_t *surface;
cairo_t *cr;
surface = cairo_linuxfb_surface_create(NULL);
cr = cairo_create(surface);
cairo_set_source_rgb(cr, 1, 1, 1);
cairo_paint(cr);
cairo_select_font_face(cr, "Sans", CAIRO_FONT_SLANT_NORMAL,
CAIRO_FONT_WEIGHT_BOLD);
cairo_set_font_size(cr, 320/6);
cairo_set_source_rgb(cr, 0, 0, 0);
cairo_move_to(cr, 0, 240/4);
cairo_show_text(cr, "Hello cairo!");
cairo_select_font_face(cr, "Sans", CAIRO_FONT_SLANT_NORMAL,
CAIRO_FONT_WEIGHT_NORMAL);
cairo_set_font_size(cr, 320/8);
cairo_set_source_rgb(cr, 0.0, 0.0, 1.0);
cairo_move_to(cr, 0, 3*240/4);
cairo_text_path(cr, "Lua calling...");
cairo_destroy(cr);
cairo_surface_destroy(surface);
return 0;
}
--
Jon Smirl
jonsm...@gmail.com
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