Fix memory leak when VNC exit

[ndsl7109256]

• Register client cleanup function when during initialization to ensure that twin_peer_t is freed properly when the client disconnects.
• Properly release resources during VNC server shutdown by unreferencin current_fb and free the framebuffer allocated for tx->framebuffer

Close #76

[ndsl7109256]

@huaxinliao Could you help me verify if there is another memory leak in Raspberry Pi?

[huaxinliao]

Through my experiments, I found the following errors on the Raspberry Pi and Ubuntu 24.04. These are the same as the ones mentioned in #76.

=================================================================
==4364==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 72 byte(s) in 1 object(s) allocated from:
    #0 0xe3cc1eae76d0 in malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:69
    #1 0xc73625ffc908 in twin_path_create src/path.c:584
    #2 0xc73625feafa4 in apps_flower_start apps/multi.c:256
    #3 0xc73625feafa4 in apps_multi_start apps/multi.c:288
    #4 0xc73625fe66d8 in main apps/main.c:109
    #5 0xe3cc1e6784c0 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
    #6 0xe3cc1e678594 in __libc_start_main_impl ../csu/libc-start.c:360
    #7 0xc73625fe71ac in _start (/home/huaxin/ndsl7109256/mado/demo-sdl+0x71ac) (BuildId: d18e212ac3a9665fa3151ef34ee47f98add57b6f)

Indirect leak of 32768 byte(s) in 1 object(s) allocated from:
    #0 0xe3cc1eae646c in realloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:85
    #1 0xc73625ff9ff4 in _twin_path_sdraw src/path.c:105
    #2 0xc73625ffad68 in twin_path_draw src/path.c:134
    #3 0xc73625ffad68 in twin_path_draw_polar src/path.c:142
    #4 0xc73625ffad68 in twin_path_arc src/path.c:231
    #5 0xc73625ffb73c in twin_path_arc_ellipse src/path.c:368
    #6 0xc73625feb19c in draw_flower apps/multi.c:241
    #7 0xc73625feb19c in apps_flower_start apps/multi.c:268
    #8 0xc73625feb19c in apps_multi_start apps/multi.c:288
    #9 0xc73625fe66d8 in main apps/main.c:109
    #10 0xe3cc1e6784c0 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
    #11 0xe3cc1e678594 in __libc_start_main_impl ../csu/libc-start.c:360
    #12 0xc73625fe71ac in _start (/home/huaxin/ndsl7109256/mado/demo-sdl+0x71ac) (BuildId: d18e212ac3a9665fa3151ef34ee47f98add57b6f)

SUMMARY: AddressSanitizer: 32840 byte(s) leaked in 2 allocation(s).

Below are the improvements I propose in apps/multi.c to address the aforementioned errors.

static void apps_flower_start(twin_screen_t *screen, int x, int y, int w, int h)
     draw_flower(path, D(3), 5);
     twin_paint_path(pixmap, 0xffe2d2d2, path);
     twin_path_destroy(stroke);
+    twin_path_destroy(path);
     twin_window_show(window);
 }

[huaxinliao]

I conducted experiments by incorporating improvements to apps/multi.c based on the current pull request and did not find any memory leak errors in the VNC backend. I consider that the improvement can be added to the pull request.

756529192.706483.-.Compressed.with.FlexClip.mp4

[jserv]

Thank @ndsl7109256 for contributing!