[libc-commits] [libc] [libc] Enable `-Wunused` and clean up found instances (PR #96949)

[Rajveer Singh Bharadwaj via libc-commits]

Rajveer100 wrote:

I have been facing this issue actually (via `ninja -C build check-libc`):

```Shell
Undefined symbols for architecture arm64:
  "__llvm_libc_19_0_0_git::internal::exit(int)", referenced from:
      __llvm_libc_19_0_0_git::BlockStore<int, 4ul, false>::pop_back() in blockstore_test.cpp.o
      __llvm_libc_19_0_0_git::BlockStore<int, 4ul, false>::get_last_blocks() in blockstore_test.cpp.o
      __llvm_libc_19_0_0_git::BlockStore<int, 4ul, true>::pop_back() in blockstore_test.cpp.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```

```Shell
Undefined symbols for architecture arm64:
  "__llvm_libc_19_0_0_git::internal::exit(int)", referenced from:
      __llvm_libc_19_0_0_git::Block<unsigned long long, 8ul>::allocate(__llvm_libc_19_0_0_git::Block<unsigned long long, 8ul>*, unsigned long, unsigned long) in block_test.cpp.o
      __llvm_libc_19_0_0_git::Block<unsigned long long, 8ul>::allocate(__llvm_libc_19_0_0_git::Block<unsigned long long, 8ul>*, unsigned long, unsigned long) in block_test.cpp.o
      __llvm_libc_19_0_0_git::Block<unsigned long long, 8ul>::allocate(__llvm_libc_19_0_0_git::Block<unsigned long long, 8ul>*, unsigned long, unsigned long) in block_test.cpp.o
      __llvm_libc_19_0_0_git::Block<unsigned long long, 8ul>::allocate(__llvm_libc_19_0_0_git::Block<unsigned long long, 8ul>*, unsigned long, unsigned long) in block_test.cpp.o
      __llvm_libc_19_0_0_git::Block<unsigned short, 2ul>::allocate(__llvm_libc_19_0_0_git::Block<unsigned short, 2ul>*, unsigned long, unsigned long) in block_test.cpp.o
      __llvm_libc_19_0_0_git::Block<unsigned short, 2ul>::allocate(__llvm_libc_19_0_0_git::Block<unsigned short, 2ul>*, unsigned long, unsigned long) in block_test.cpp.o
      __llvm_libc_19_0_0_git::Block<unsigned short, 2ul>::allocate(__llvm_libc_19_0_0_git::Block<unsigned short, 2ul>*, unsigned long, unsigned long) in block_test.cpp.o
      __llvm_libc_19_0_0_git::Block<unsigned short, 2ul>::allocate(__llvm_libc_19_0_0_git::Block<unsigned short, 2ul>*, unsigned long, unsigned long) in block_test.cpp.o
      ...
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```

https://github.com/llvm/llvm-project/pull/96949