incompatible pointer type

[Zucca]

I'm trying to build chocobar on a arm64 using llvm profile.

Code: Select all

 ./build.sh
++ dirname -- ./build.sh
+ cd .
+ bin=chocobar-9999
+ : /var/tmp/portage/gui-apps/chocobar-9999/image/usr
+ : /var/tmp/portage/gui-apps/chocobar-9999/image/bin
+ CFLAGS='-march=armv8.6-a -mcpu=apple-m2 -O2 -Wall -Wextra -Wno-unused-function -Wno-unused-parameter'
+ PKG_CONFIG=pkg-config
++ pkg-config --variable=pkgdatadir wayland-protocols
+ WAYLAND_PROTOCOLS=//usr/share/wayland-protocols
++ pkg-config --variable=wayland_scanner wayland-scanner
+ WAYLAND_SCANNER=/usr/bin/wayland-scanner
+ PKGS='wayland-client pixman-1 fcft'
++ pkg-config --cflags wayland-client pixman-1 fcft
+ CFLAGS='-march=armv8.6-a -mcpu=apple-m2 -O2 -Wall -Wextra -Wno-unused-function -Wno-unused-parameter -I/usr/lib64/libffi/include -I/usr/include/harfbuzz -I/usr/include/freetype2 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -DUTF8PROC_EXPORTS -I/usr/include/pixman-1'
++ pkg-config --libs wayland-client pixman-1 fcft
+ LDLIBS=' -lwayland-client -lm -lfcft -lpixman-1'
+ '[' 0 -gt 0 ']'
+ '[' -z ']'
+ for protocol in single-pixel-buffer-v1 viewporter wlr-layer-shell-unstable-v1 xdg-shell xdg-foreign-unstable-v2
+ '[' -e single-pixel-buffer-v1-protocol.c -a -e single-pixel-buffer-v1-protocol.h ']'
+ protocolxml=protocols/single-pixel-buffer-v1.xml
+ '[' '!' -e protocols/single-pixel-buffer-v1.xml ']'
+ for protocolxml in "$WAYLAND_PROTOCOLS"/*/*/"$protocol".xml
+ break
+ /usr/bin/wayland-scanner private-code //usr/share/wayland-protocols/staging/single-pixel-buffer/single-pixel-buffer-v1.xml single-pixel-buffer-v1-protocol.c
+ /usr/bin/wayland-scanner client-header //usr/share/wayland-protocols/staging/single-pixel-buffer/single-pixel-buffer-v1.xml single-pixel-buffer-v1-protocol.h
+ for protocol in single-pixel-buffer-v1 viewporter wlr-layer-shell-unstable-v1 xdg-shell xdg-foreign-unstable-v2
+ '[' -e viewporter-protocol.c -a -e viewporter-protocol.h ']'
+ protocolxml=protocols/viewporter.xml
+ '[' '!' -e protocols/viewporter.xml ']'
+ for protocolxml in "$WAYLAND_PROTOCOLS"/*/*/"$protocol".xml
+ break
+ /usr/bin/wayland-scanner private-code //usr/share/wayland-protocols/stable/viewporter/viewporter.xml viewporter-protocol.c
+ /usr/bin/wayland-scanner client-header //usr/share/wayland-protocols/stable/viewporter/viewporter.xml viewporter-protocol.h
+ for protocol in single-pixel-buffer-v1 viewporter wlr-layer-shell-unstable-v1 xdg-shell xdg-foreign-unstable-v2
+ '[' -e wlr-layer-shell-unstable-v1-protocol.c -a -e wlr-layer-shell-unstable-v1-protocol.h ']'
+ protocolxml=protocols/wlr-layer-shell-unstable-v1.xml
+ '[' '!' -e protocols/wlr-layer-shell-unstable-v1.xml ']'
+ /usr/bin/wayland-scanner private-code protocols/wlr-layer-shell-unstable-v1.xml wlr-layer-shell-unstable-v1-protocol.c
+ /usr/bin/wayland-scanner client-header protocols/wlr-layer-shell-unstable-v1.xml wlr-layer-shell-unstable-v1-protocol.h
+ for protocol in single-pixel-buffer-v1 viewporter wlr-layer-shell-unstable-v1 xdg-shell xdg-foreign-unstable-v2
+ '[' -e xdg-shell-protocol.c -a -e xdg-shell-protocol.h ']'
+ protocolxml=protocols/xdg-shell.xml
+ '[' '!' -e protocols/xdg-shell.xml ']'
+ for protocolxml in "$WAYLAND_PROTOCOLS"/*/*/"$protocol".xml
+ break
+ /usr/bin/wayland-scanner private-code //usr/share/wayland-protocols/stable/xdg-shell/xdg-shell.xml xdg-shell-protocol.c
+ /usr/bin/wayland-scanner client-header //usr/share/wayland-protocols/stable/xdg-shell/xdg-shell.xml xdg-shell-protocol.h
+ for protocol in single-pixel-buffer-v1 viewporter wlr-layer-shell-unstable-v1 xdg-shell xdg-foreign-unstable-v2
+ '[' -e xdg-foreign-unstable-v2-protocol.c -a -e xdg-foreign-unstable-v2-protocol.h ']'
+ protocolxml=protocols/xdg-foreign-unstable-v2.xml
+ '[' '!' -e protocols/xdg-foreign-unstable-v2.xml ']'
+ for protocolxml in "$WAYLAND_PROTOCOLS"/*/*/"$protocol".xml
+ break
+ /usr/bin/wayland-scanner private-code //usr/share/wayland-protocols/unstable/xdg-foreign/xdg-foreign-unstable-v2.xml xdg-foreign-unstable-v2-protocol.c
+ /usr/bin/wayland-scanner client-header //usr/share/wayland-protocols/unstable/xdg-foreign/xdg-foreign-unstable-v2.xml xdg-foreign-unstable-v2-protocol.h
+ '[' -e /var/tmp/portage/gui-apps/chocobar-9999/image/bin ']'
+ mkdir -p /var/tmp/portage/gui-apps/chocobar-9999/image/bin
+ cc chocobar.c single-pixel-buffer-v1-protocol.c util.c viewporter-protocol.c wlr-layer-shell-unstable-v1-protocol.c xdg-foreign-unstable-v2-protocol.c xdg-shell-protocol.c -march=armv8.6-a -mcpu=apple-m2 -O2 -Wall -Wextra -Wno-unused-function -Wno-unused-parameter -I/usr/lib64/libffi/include -I/usr/include/harfbuzz -I/usr/include/freetype2 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -DUTF8PROC_EXPORTS -I/usr/include/pixman-1 -lwayland-client -lm -lfcft -lpixman-1 -o /var/tmp/portage/gui-apps/chocobar-9999/image/bin/chocobar-9999
In file included from chocobar.c:11:
drwl/drwl.h: In function ‘drwl_init’:
drwl/drwl.h:88:9: warning: ‘fcft_set_scaling_filter’ is deprecated [-Wdeprecated-declarations]
   88 |         fcft_set_scaling_filter(FCFT_SCALING_FILTER_LANCZOS3);
      |         ^~~~~~~~~~~~~~~~~~~~~~~
In file included from drwl/drwl.h:33:
/usr/include/fcft/fcft.h:190:6: note: declared here
  190 | bool fcft_set_scaling_filter(enum fcft_scaling_filter filter) FCFT_DEPRECATED;
      |      ^~~~~~~~~~~~~~~~~~~~~~~
chocobar.c: At top level:
chocobar.c:287:18: error: initialization of ‘void (*)(void *, struct wl_surface *, struct wl_output *)’ from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  287 |         .enter = noop,
      |                  ^~~~
chocobar.c:287:18: note: (near initialization for ‘ss_surface_listener.enter’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:288:18: error: initialization of ‘void (*)(void *, struct wl_surface *, struct wl_output *)’ from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  288 |         .leave = noop,
      |                  ^~~~
chocobar.c:288:18: note: (near initialization for ‘ss_surface_listener.leave’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:290:39: error: initialization of ‘void (*)(void *, struct wl_surface *, uint32_t)’ {aka ‘void (*)(void *, struct wl_surface *, unsigned int)’} from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  290 |         .preferred_buffer_transform = noop,
      |                                       ^~~~
chocobar.c:290:39: note: (near initialization for ‘ss_surface_listener.preferred_buffer_transform’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:663:18: error: initialization of ‘void (*)(void *, struct wl_surface *, struct wl_output *)’ from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  663 |         .enter = noop,
      |                  ^~~~
chocobar.c:663:18: note: (near initialization for ‘so_surface_listener.enter’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:664:18: error: initialization of ‘void (*)(void *, struct wl_surface *, struct wl_output *)’ from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  664 |         .leave = noop,
      |                  ^~~~
chocobar.c:664:18: note: (near initialization for ‘so_surface_listener.leave’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:665:35: error: initialization of ‘void (*)(void *, struct wl_surface *, int32_t)’ {aka ‘void (*)(void *, struct wl_surface *, int)’} from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  665 |         .preferred_buffer_scale = noop,
      |                                   ^~~~
chocobar.c:665:35: note: (near initialization for ‘so_surface_listener.preferred_buffer_scale’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:666:39: error: initialization of ‘void (*)(void *, struct wl_surface *, uint32_t)’ {aka ‘void (*)(void *, struct wl_surface *, unsigned int)’} from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  666 |         .preferred_buffer_transform = noop,
      |                                       ^~~~
chocobar.c:666:39: note: (near initialization for ‘so_surface_listener.preferred_buffer_transform’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:755:21: error: initialization of ‘void (*)(void *, struct wl_output *, int32_t,  int32_t,  int32_t,  int32_t,  int32_t,  const char *, const char *, int32_t)’ {aka ‘void (*)(void *, struct wl_output *, int,  int,  int,  int,  int,  const char *, const char *, int)’} from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  755 |         .geometry = noop,
      |                     ^~~~
chocobar.c:755:21: note: (near initialization for ‘output_listener.geometry’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:756:17: error: initialization of ‘void (*)(void *, struct wl_output *, uint32_t,  int32_t,  int32_t,  int32_t)’ {aka ‘void (*)(void *, struct wl_output *, unsigned int,  int,  int,  int)’} from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  756 |         .mode = noop,
      |                 ^~~~
chocobar.c:756:17: note: (near initialization for ‘output_listener.mode’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:757:17: error: initialization of ‘void (*)(void *, struct wl_output *)’ from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  757 |         .done = noop,
      |                 ^~~~
chocobar.c:757:17: note: (near initialization for ‘output_listener.done’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:758:18: error: initialization of ‘void (*)(void *, struct wl_output *, int32_t)’ {aka ‘void (*)(void *, struct wl_output *, int)’} from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  758 |         .scale = noop,
      |                  ^~~~
chocobar.c:758:18: note: (near initialization for ‘output_listener.scale’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:759:24: error: initialization of ‘void (*)(void *, struct wl_output *, const char *)’ from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  759 |         .description = noop,
      |                        ^~~~
chocobar.c:759:24: note: (near initialization for ‘output_listener.description’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:969:26: error: initialization of ‘void (*)(void *, struct wl_pointer *, uint32_t,  int32_t)’ {aka ‘void (*)(void *, struct wl_pointer *, unsigned int,  int)’} from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  969 |         .axis_value120 = noop,
      |                          ^~~~
chocobar.c:969:26: note: (near initialization for ‘pointer_listener.axis_value120’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~
chocobar.c:991:17: error: initialization of ‘void (*)(void *, struct wl_seat *, const char *)’ from incompatible pointer type ‘void (*)(void)’ [-Wincompatible-pointer-types]
  991 |         .name = noop,
      |                 ^~~~
chocobar.c:991:17: note: (near initialization for ‘seat_listener.name’)
chocobar.c:164:13: note: ‘noop’ declared here
  164 | static void noop(){}
      |             ^~~~

Is llvm/clang just very cautious here? Does chocobar.c have bad programing practices?
I'm not a C programmer, but these errors indicate that some pointers aren't correctly initialized, so the compiler errors out instead of trying to guess and possible make insecure binary.

[John R. Graham]

Way back in the C89/C90 standard (and before), this construct wasn't even a warning. I believe that in C99 it became a warning and, at some point thereafter, an error. You might be able to Band-Aid this by specifying application-targeted CFLAGS containing "-std=C89" (or maybe a later version where only warnings would be thrown).

Defining a function like

Code: Select all

void myfunc() {};

classically meant the function was defined without a "prototype": function pointers with prototype information could be assigned a pointer to a prototype-less function, but you can probably see the possibilities for problems this looseness allows.

- John

[grknight]

https://wiki.gentoo.org/wiki/Modern_C_porting

[Hu]

The Wiki page that grknight linked is a good primer. For this specific case, the solution is a bit easier. Based on the name of the function (noop) and its definition that the compiler printed in the diagnostic, we can tell that the author wants a function which does nothing and returns nothing. It exists solely to avoid putting nullptr in the function pointer field, presumably because the caller assumes that the pointer can always be called and does not have a special case to skip calling a pointer that is equal to nullptr. Therefore, the spot fix is to change the prototype of noop to match the prototype the compiler wants. This is slightly complicated by the fact that the author uses noop with several different prototypes. If I were to write a minimal fix, I would:

• Notify upstream. This needs to be fixed everywhere, not just in Gentoo.
• While waiting, remove the definition of noop, and add definitions such as:

  Code: Select all

  static void noop_1(void *, struct wl_output *) {}
  static void noop_2(void *, struct wl_output *, const char *) {}
  static void noop_3(void *, struct wl_output *, int32_t) {}
  static void noop_4(void *, struct wl_output *, int32_t,  int32_t,  int32_t,  int32_t,  int32_t,  const char *, const char *, int32_t) {}
  static void noop_5(void *, struct wl_output *, uint32_t,  int32_t,  int32_t,  int32_t) {}
  static void noop_6(void *, struct wl_pointer *, uint32_t,  int32_t) {}
  static void noop_7(void *, struct wl_seat *, const char *) {}
  static void noop_8(void *, struct wl_surface *, int32_t) {}
  static void noop_9(void *, struct wl_surface *, struct wl_output *) {}
  static void noop_10(void *, struct wl_surface *, uint32_t) {}
  

• Then use each noop_N in the corresponding initialization. You can work from the compiler error messages shown to find which is which, or rely on the fact that if you get it right, the warning will go away without needing a cast. You want the initialization lines to read like:

  Code: Select all

  .preferred_buffer_transform = noop_10,

Better names than noop_N would make this more readable. I didn't want to try embedding argument-specific decorations into each name. That is left as an exercise for the reader.

Post back if you need more help.

[Zucca]

So I had some time to dig into this again.
I'll raise an issue to upstream.

Chocobar uses drwl header library... but an older version.
The newest version of drwl is incompatible with chocobar. That also might need an issue to be raised.

Meanwhile I'll use

Code: Select all

CFLAGS="${CFLAGS} -Wno-error=incompatible-pointer-types"

... until upstream makes a fix.