[C++] unused-variable warnings

[huberylee]

Describe the bug, including details regarding any error messages, version, and platform.

In file included from /workspace/arrow/cpp/src/arrow/array/array_base.h:26:
/workspace/arrow/cpp/src/arrow/array/data.h:452:19: warning: unused variable 'buffer_length' [-Wunused-variable]
    const int64_t buffer_length = buffers[i].size / static_cast<int64_t>(sizeof(T));
                  ^
/workspace/arrow/cpp/src/arrow/array/data.h:467:19: warning: unused variable 'buffer_length' [-Wunused-variable]
    const int64_t buffer_length = buffers[i].size / static_cast<int64_t>(sizeof(T));
                  ^
2 warnings generated.

Component(s)

C++

[mapleFU]

@pitrou @felipecrv

Would you think we can enable more compile options like unused-variable?

[felipecrv]

@pitrou @felipecrv

Would you think we can enable more compile options like unused-variable?

It is enabled. This is only an issue on non-debug builds because the variable is only used for an assert. I can send a fix (I have a commit with a fix from days ago on my computer).