[libc] Enable -Wunused and clean up found instances

[Rajveer100]

Resolves #96689

Updates compile_options in the LLVMLibCObjectRules CMake script.

[Rajveer100]

@nickdesaulniers
I am not quite sure about the clean up part.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Rajveer Singh Bharadwaj (Rajveer100)

Changes

Resolves #96689

Updates compile_options in the LLVMLibCObjectRules CMake script.

---

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

1 Files Affected:

• (modified) libc/cmake/modules/LLVMLibCObjectRules.cmake (+5)

diff --git a/libc/cmake/modules/LLVMLibCObjectRules.cmake b/libc/cmake/modules/LLVMLibCObjectRules.cmake
index 134c5143d6d61..c53548a1294e4 100644
--- a/libc/cmake/modules/LLVMLibCObjectRules.cmake
+++ b/libc/cmake/modules/LLVMLibCObjectRules.cmake
@@ -50,6 +50,8 @@ function(create_object_library fq_target_name)
   _get_common_compile_options(compile_options "${ADD_OBJECT_FLAGS}")
   list(APPEND compile_options ${ADD_OBJECT_COMPILE_OPTIONS})
 
+  list(APPEND compile_options -Wunused)
+
   add_library(
     ${fq_target_name}
     EXCLUDE_FROM_ALL
@@ -251,6 +253,9 @@ function(create_entrypoint_object fq_target_name)
   endif()
 
   _get_common_compile_options(common_compile_options "${ADD_ENTRYPOINT_OBJ_FLAGS}")
+
+  list(APPEND common_compile_options -Wunused)
+
   list(APPEND common_compile_options ${ADD_ENTRYPOINT_OBJ_COMPILE_OPTIONS})
   get_fq_deps_list(fq_deps_list ${ADD_ENTRYPOINT_OBJ_DEPENDS})
   set(full_deps_list ${fq_deps_list} libc.src.__support.common)

[Rajveer100]

@michaelrj-google
Could you review this, looks like Nick is on leave?

[SchrodingerZhu]

any instances found by the warning?

[Rajveer100]

Well, I might not be checking the right way, I did not see any warnings show up (apart from -undefined) when doing ninja -C build.

How would you do it @SchrodingerZhu ?

[asudarsa]

Well, I might not be checking the right way, I did not see any warnings show up (apart from -undefined) when doing ninja -C build.

How would you do it @SchrodingerZhu ?

One possible way might be to reintroduce the unused variables mentioned in the comment here (#96591 (comment)) and rebuild to see if warnings are emitted with your change.

[michaelrj-google]

hi, yes I can review this. It got lost in my inbox so I just now saw it. For cleanup that's just running a build (probably with ninja check-libc) and finding what errors show up and fixing them. I can give more instruction if you would like.

[Rajveer100]

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

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)

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)

[jhuber6]

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

This is probably related to #97642

[Rajveer100]

@michaelrj-google
Just noticed this had been lying around for a while. Regardless of adding the compile flag, -Wunused error is enabled, I checked this by adding few unused instances (like int some_var = 0).

It was not triggered for the the specific case:

  FPBits sk_cy(sin_k_cos_y.hi);
  FPBits ck_sy(cos_k_sin_y.hi);

But works for:

  FPBits sk_cy;

Considering this, I think this PR and the linked issue can be closed?

[michaelrj-google]

I think -Wunused is included in -Wall and -Wextra, so closing this PR and issue SGTM.

[Rajveer100]

Great, closing this one.