Fix warnings on 32-bit platforms

[voidbert]

Fixed code that assumed the size of some integer types to be a fixed number of bytes, when it can very between platforms. The warnings fixed were:

• Wrong printf formats for size_t. Now, the platform-independent %zu (C99 required);
• time_t may be less than 64 bits, requiring a cast to a bigger size if a left shift by 32 bits is used.
• POS_FROM_PARENT may assume a value too large for ssize_t.

I didn't test if these warnings caused any runtime errors, but they can do so, so it's better to have them fixed.

[artemsen]

Do we really need these type casts?
0xffffffff fits uint32_t. Also color is always 32 bits.

[voidbert]

On 32-bit systems, 0xffffffff will be considered a 4-byte unsigned int by compilers, as it can't fit in an int without overflowing. Also, ssize_t num will be a 4-byte int (not guaranteed by the C spec, but what compilers usually do). The compiler will emit a warning because these two different types are being compared, and the compiler doesn't know whether it should generate a signed or unsigned comparison. The cast to uint64_t assures that these two values can be safely compared on both 32-bit and 64-bit systems. On 64-bit systems, because this code checks for the validity of a color, num can be greater than 32-bits (it's inputted by the user in the configuration file). A cast of num to uint32_t wouldn't suffice, as values higher than 0xffffffff would be accepted as valid colors, as they'd be truncated before the comparison.

[artemsen]

It would be better to use one style for printf.

[voidbert]

Sorry, but I don't know what you mean by this. PRIx64 is the best way to print an uint64_t independently of the size unsigned long ("%lx") or unsigned long long ("%llx") might have. Another option would be casting the value in the arguments to an unsigned long long, and %llx can be used instead of PRIx64 . I can patch that in if you wish.

[artemsen]

I don't see a reason to change this. What the purpose?

[voidbert]

0xffffffff may be too large for an ssize_t, and some functions (ui_get_x and ui_get_y) return this value as an ssize_t. I see that POS_FROM_PARENT is a special return value: normal positions can be returned, so can this very large value, which has a special meaning. This way, SSIZE_MAX is for sure the greatest value that can fit in an ssize_t.

[voidbert]

I hereby attach the warnings that resulted from compiling swayimg on GCC 13.2.0, on a 32-bit glibc system.

warnings.txt

ninja: Entering directory `/root/swayimg/build'
[1/34] Generating xdg-shell-protocol.c with a custom command
[2/34] Generating xdg-shell-protocol.h with a custom command
[3/34] Compiling C object swayimg.p/meson-generated_.._xdg-shell-protocol.c.o
[4/34] Compiling C object swayimg.p/src_action.c.o
[5/34] Compiling C object swayimg.p/src_image.c.o
[6/34] Compiling C object swayimg.p/src_cache.c.o
[7/34] Compiling C object swayimg.p/src_config.c.o
../src/config.c: In function 'load_config':
../src/config.c:122:65: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  122 |                 fprintf(stderr, "Invalid section define in %s:%lu\n", path,
      |                                                               ~~^
      |                                                                 |
      |                                                                 long unsigned int
      |                                                               %u
  123 |                         line_num);
      |                         ~~~~~~~~                                 
      |                         |
      |                         size_t {aka unsigned int}
../src/config.c:135:63: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  135 |             fprintf(stderr, "Invalid key=value format in %s:%lu\n", path,
      |                                                             ~~^
      |                                                               |
      |                                                               long unsigned int
      |                                                             %u
  136 |                     line_num);
      |                     ~~~~~~~~                                   
      |                     |
      |                     size_t {aka unsigned int}
../src/config.c:154:60: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  154 |             fprintf(stderr, "Invalid configuration in %s:%lu\n", path,
      |                                                          ~~^
      |                                                            |
      |                                                            long unsigned int
      |                                                          %u
  155 |                     line_num);
      |                     ~~~~~~~~                                
      |                     |
      |                     size_t {aka unsigned int}
../src/config.c: In function 'config_to_color':
../src/config.c:302:58: warning: comparison of integer expressions of different signedness: 'ssize_t' {aka 'int'} and 'unsigned int' [-Wsign-compare]
  302 |     if (!str_to_num(text, 0, &num, 16) || num < 0 || num > 0xffffffff) {
      |                                                          ^
[8/34] Compiling C object swayimg.p/src_font.c.o
[9/34] Compiling C object swayimg.p/src_keybind.c.o
[10/34] Compiling C object swayimg.p/src_main.c.o
../src/main.c: In function 'sway_setup':
../src/main.c:170:27: warning: comparison of integer expressions of different signedness: 'ssize_t' {aka 'int'} and 'unsigned int' [-Wsign-compare]
  170 |     absolute = ui_get_x() != POS_FROM_PARENT && ui_get_y() != POS_FROM_PARENT;
      |                           ^~
../src/main.c:170:60: warning: comparison of integer expressions of different signedness: 'ssize_t' {aka 'int'} and 'unsigned int' [-Wsign-compare]
  170 |     absolute = ui_get_x() != POS_FROM_PARENT && ui_get_y() != POS_FROM_PARENT;
      |                                                            ^~
[11/34] Compiling C object swayimg.p/src_imagelist.c.o
[12/34] Compiling C object swayimg.p/src_info.c.o
../src/info.c: In function 'info_update':
../src/info.c:400:45: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  400 |         snprintf(buffer, sizeof(buffer), "%lu of %lu", ctx.frame + 1,
      |                                           ~~^          ~~~~~~~~~~~~~
      |                                             |                    |
      |                                             long unsigned int    size_t {aka unsigned int}
      |                                           %u
../src/info.c:400:52: warning: format '%lu' expects argument of type 'long unsigned int', but argument 5 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  400 |         snprintf(buffer, sizeof(buffer), "%lu of %lu", ctx.frame + 1,
      |                                                  ~~^
      |                                                    |
      |                                                    long unsigned int
      |                                                  %u
  401 |                  ctx.frame_total);
      |                  ~~~~~~~~~~~~~~~                    
      |                     |
      |                     size_t {aka unsigned int}
../src/info.c:407:45: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  407 |         snprintf(buffer, sizeof(buffer), "%lu of %lu", ctx.index + 1,
      |                                           ~~^          ~~~~~~~~~~~~~
      |                                             |                    |
      |                                             long unsigned int    size_t {aka unsigned int}
      |                                           %u
../src/info.c:407:52: warning: format '%lu' expects argument of type 'long unsigned int', but argument 5 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  407 |         snprintf(buffer, sizeof(buffer), "%lu of %lu", ctx.index + 1,
      |                                                  ~~^
      |                                                    |
      |                                                    long unsigned int
      |                                                  %u
  408 |                  image_list_size());
      |                  ~~~~~~~~~~~~~~~~~                  
      |                  |
      |                  size_t {aka unsigned int}
../src/info.c:416:49: warning: format '%ld' expects argument of type 'long int', but argument 4 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  416 |             snprintf(buffer, sizeof(buffer), "%ld%%", ctx.scale);
      |                                               ~~^     ~~~~~~~~~
      |                                                 |        |
      |                                                 long int size_t {aka unsigned int}
      |                                               %d
../src/info.c:426:49: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  426 |             snprintf(buffer, sizeof(buffer), "%lux%lu", ctx.width, ctx.height);
      |                                               ~~^       ~~~~~~~~~
      |                                                 |          |
      |                                                 |          size_t {aka unsigned int}
      |                                                 long unsigned int
      |                                               %u
../src/info.c:426:53: warning: format '%lu' expects argument of type 'long unsigned int', but argument 5 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
  426 |             snprintf(buffer, sizeof(buffer), "%lux%lu", ctx.width, ctx.height);
      |                                                   ~~^              ~~~~~~~~~~
      |                                                     |                 |
      |                                                     long unsigned int size_t {aka unsigned int}
      |                                                   %u
[13/34] Compiling C object swayimg.p/src_text.c.o
[14/34] Compiling C object swayimg.p/src_str.c.o
[15/34] Compiling C object swayimg.p/src_loader.c.o
[16/34] Compiling C object swayimg.p/src_sway.c.o
[17/34] Compiling C object swayimg.p/src_formats_pnm.c.o
[18/34] Compiling C object swayimg.p/src_ui.c.o
../src/ui.c: In function 'create_buffer':
../src/ui.c:161:25: warning: left shift count >= width of type [-Wshift-count-overflow]
  161 |              (ts.tv_sec << 32) | ts.tv_nsec);
      |                         ^~
../src/ui.c: In function 'ui_create':
../src/ui.c:701:47: warning: left shift count >= width of type [-Wshift-count-overflow]
  701 |         const uint64_t timestamp = (ts.tv_sec << 32) | ts.tv_nsec;
      |                                               ^~
In file included from ../src/ui.c:7:
./buildcfg.h:8:18: warning: format '%lx' expects argument of type 'long unsigned int', but argument 4 has type 'uint64_t' {aka 'long long unsigned int'} [-Wformat=]
    8 | #define APP_NAME "swayimg"
      |                  ^~~~~~~~~
../src/ui.c:702:42: note: in expansion of macro 'APP_NAME'
  702 |         snprintf(app_id, sizeof(app_id), APP_NAME "_%lx", timestamp);
      |                                          ^~~~~~~~
../src/ui.c:702:55: note: format string is defined here
  702 |         snprintf(app_id, sizeof(app_id), APP_NAME "_%lx", timestamp);
      |                                                     ~~^
      |                                                       |
      |                                                       long unsigned int
      |                                                     %llx
[19/34] Compiling C object swayimg.p/src_formats_bmp.c.o
[20/34] Compiling C object swayimg.p/src_formats_tga.c.o
[21/34] Compiling C object swayimg.p/src_pixmap.c.o
[22/34] Compiling C object swayimg.p/src_exif.c.o
[23/34] Compiling C object swayimg.p/src_viewer.c.o
[24/34] Compiling C object swayimg.p/src_formats_avif.c.o
[25/34] Compiling C object swayimg.p/src_formats_jpeg.c.o
[26/34] Compiling C object swayimg.p/src_formats_heif.c.o
[27/34] Compiling C object swayimg.p/src_formats_jxl.c.o
[28/34] Compiling C object swayimg.p/src_formats_gif.c.o
[29/34] Compiling C object swayimg.p/src_formats_png.c.o
[30/34] Compiling C object swayimg.p/src_formats_webp.c.o
[31/34] Compiling C object swayimg.p/src_formats_exr.c.o
[32/34] Compiling C object swayimg.p/src_formats_tiff.c.o
[33/34] Compiling C object swayimg.p/src_formats_svg.c.o
[34/34] Linking target swayimg
INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /bin/ninja -C /root/swayimg/build

[artemsen]

Sounds reasonable, thank you!