Everywhere: Switch from (void) to [[maybe_unused]] (#4473)

Problem:
- `(void)` simply casts the expression to void. This is understood to
  indicate that it is ignored, but this is really a compiler trick to
  get the compiler to not generate a warning.

Solution:
- Use the `[[maybe_unused]]` attribute to indicate the value is unused.

Note:
- Functions taking a `(void)` argument list have also been changed to
  `()` because this is not needed and shows up in the same grep
  command.

1 files changed, 2 insertions, 5 deletions

diff --git a/Userland/df.cpp b/Userland/df.cpp
index d4b1d3cfc8..53a79eb7aa 100644
--- a/Userland/df.cpp
+++ b/Userland/df.cpp
@@ -78,14 +78,11 @@ int main(int argc, char** argv)
         auto fs = fs_object.get("class_name").to_string();
         auto total_block_count = fs_object.get("total_block_count").to_u32();
         auto free_block_count = fs_object.get("free_block_count").to_u32();
-        auto total_inode_count = fs_object.get("total_inode_count").to_u32();
-        auto free_inode_count = fs_object.get("free_inode_count").to_u32();
+        [[maybe_unused]] auto total_inode_count = fs_object.get("total_inode_count").to_u32();
+        [[maybe_unused]] auto free_inode_count = fs_object.get("free_inode_count").to_u32();
         auto block_size = fs_object.get("block_size").to_u32();
         auto mount_point = fs_object.get("mount_point").to_string();
 
-        (void)total_inode_count;
-        (void)free_inode_count;
-
         printf("%-10s", fs.characters());
 
         if (flag_human_readable) {