Improve C standard compliance.

- Don't cast between object and function pointers.
- Use standard compliant `__VA_ARGS__` in macros.
- Add explicit `__extension__` on unnamed union in struct (it's a GNU
  extension).
- Remove ; after function definitions.
- Replace `const T foo = 3;` for integral types `T` with `enum { foo = 3 };`.
  Folding integral constants like that as compile time constants is a GNU
  extension. Arrays allocated with `foo` as dimension are VLAs on strictly
  compliant C99 compilers.
- Replace empty initialiser list `{}` with zero-initialiser-list `{0}`.
  The former is a GNU extension meaning the latter.
- Cast `T*` (where `T != void`) to `void *` in format arguments. While any
  object pointer can be implicitly converted to and from `void *`, this
  conversion does not happen in variadic function calls.
- Replace arithmetic on `void *` with arithmetic on `char *`. The former
  is non-compliant.
- Replace non-`int`-derived types (like `uint16_t`, which is
  `short`-derived) in bit fields with `int`-derived types. Using any type
  other than `int` or `unsigned int` (or any of their aliases) in bit
  fields is a GNU extension.

1 files changed, 2 insertions, 2 deletions

diff --git a/auto_tests/toxav_many_test.c b/auto_tests/toxav_many_test.c
index 9a58e648..5d889032 100644
--- a/auto_tests/toxav_many_test.c
+++ b/auto_tests/toxav_many_test.c
@@ -63,7 +63,7 @@ void t_toxav_call_cb(ToxAV *av, uint32_t friend_number, bool audio_enabled, bool
 }
 void t_toxav_call_state_cb(ToxAV *av, uint32_t friend_number, uint32_t state, void *user_data)
 {
-    printf("Handling CALL STATE callback: %d %p\n", state, av);
+    printf("Handling CALL STATE callback: %d %p\n", state, (void *)av);
     ((CallControl *)user_data)[friend_number].state = state;
 }
 void t_toxav_receive_video_frame_cb(ToxAV *av, uint32_t friend_number,
@@ -188,7 +188,7 @@ void *call_thread(void *pd)
         toxav_call_control(AliceAV, friend_number, TOXAV_CALL_CONTROL_CANCEL, &rc);
 
         if (rc != TOXAV_ERR_CALL_CONTROL_OK) {
-            printf("toxav_call_control failed: %d %p %p\n", rc, AliceAV, BobAV);
+            printf("toxav_call_control failed: %d %p %p\n", rc, (void *)AliceAV, (void *)BobAV);
         }
     }