Initialize `Allocation` to eliminate compile error

[GOGOYAO]

Class Allocation is not initialized and I will get a compile error like this.

error: ‘worklist.absl::lts_20220623::InlinedVector<absl::lts_20220623::cord_internal::CordRep*, 2, std::allocator<absl::lts_20220623::cord_internal::CordRep*> >::storage_.absl::lts_20220623::inlined_vector_internal::Storage<absl::lts_20220623::cord_internal::CordRep*, 2, std::allocator<absl::lts_20220623::cord_internal::CordRep*> >::data_.absl::lts_20220623::inlined_vector_internal::Storage<absl::lts_20220623::cord_internal::CordRep*, 2, std::allocator<absl::lts_20220623::cord_internal::CordRep*> >::Data::allocated.absl::lts_20220623::inlined_vector_internal::Storage<absl::lts_20220623::cord_internal::CordRep*, 2, std::allocator<absl::lts_20220623::cord_internal::CordRep*> >::Allocated::allocated_capacity’ may be used uninitialized [-Werror=maybe-uninitialized]

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[derekmauro]

1. We need the CLA.
2. I can't reproduce this problem. Can you provide reproduction instructions?

[GOGOYAO]

1. We need the CLA.
2. I can't reproduce this problem. Can you provide reproduction instructions?

1. Done
2. I compile it like this.

My directory tree is like this.

$ tree
.
|-- bld
|-- cmake
|   `-- abseil.cmake
|-- CMakeLists.txt
`-- main.cpp

2 directories, 3 files

main.cpp

#include "absl/container/flat_hash_set.h"

int main(int argc, char** argv) {
    absl::flat_hash_set<int> set;
    return 0;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.20.2)

project(test-abseil
    VERSION 1.0
    LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
message(STATUS "cxx version ${CMAKE_CXX_STANDARD}")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Werror -O3 -g -mavx2")
message(STATUS "cxx_flags ${CMAKE_CXX_FLAGS}")

set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake;${CMAKE_MODULE_PATH}")

include_directories(include)

# abseil
include(abseil)

add_executable(main main.cpp)
target_link_libraries(main absl::random_random absl::strings absl::time absl::flat_hash_map absl::synchronization)

cmake/abseil.cmake

include(FetchContent)

set(GTEST_GIT_TAG  master)
set(GTEST_GIT_URL  https://github.com/abseil/abseil-cpp.git)

FetchContent_Declare(
    abseil
    GIT_REPOSITORY    ${GTEST_GIT_URL}
    GIT_TAG           ${GTEST_GIT_TAG}
    )

FetchContent_MakeAvailable(abseil)

I compile it with cmd mkdir bld; cmake -S . -B bld && cmake --build bld and I get error as follows.

In file included from /root/workspace/tmp/bld/_deps/abseil-src/absl/container/inlined_vector.h:53,
                 from /root/workspace/tmp/bld/_deps/abseil-src/absl/strings/cord.h:78,
                 from /root/workspace/tmp/bld/_deps/abseil-src/absl/strings/cord.cc:15:
In member function ‘absl::inlined_vector_internal::SizeType<A> absl::inlined_vector_internal::Storage<T, N, A>::GetAllocatedCapacity() const [with T = absl::cord_internal::CordRep*; long unsigned int N = 2; A = std::allocator<absl::cord_internal::CordRep*>]’,
    inlined from ‘void absl::inlined_vector_internal::Storage<T, N, A>::DeallocateIfAllocated() [with T = absl::cord_internal::CordRep*; long unsigned int N = 2; A = std::allocator<absl::cord_internal::CordRep*>]’ at /root/workspace/tmp/bld/_deps/abseil-src/absl/container/internal/inlined_vector.h:452:35,
    inlined from ‘absl::inlined_vector_internal::Storage<T, N, A>::~Storage() [with T = absl::cord_internal::CordRep*; long unsigned int N = 2; A = std::allocator<absl::cord_internal::CordRep*>]’ at /root/workspace/tmp/bld/_deps/abseil-src/absl/container/internal/inlined_vector.h:323:28,
    inlined from ‘absl::InlinedVector<T, N, A>::~InlinedVector() [with T = absl::cord_internal::CordRep*; long unsigned int N = 2; A = std::allocator<absl::cord_internal::CordRep*>]’ at /root/workspace/tmp/bld/_deps/abseil-src/absl/container/inlined_vector.h:256:21,
    inlined from ‘bool absl::VerifyNode(absl::cord_internal::CordRep*, absl::cord_internal::CordRep*, bool)’ at /root/workspace/tmp/bld/_deps/abseil-src/absl/strings/cord.cc:1308:1:
/root/workspace/tmp/bld/_deps/abseil-src/absl/container/internal/inlined_vector.h:360:28: error: ‘worklist.absl::InlinedVector<absl::cord_internal::CordRep*, 2, std::allocator<absl::cord_internal::CordRep*> >::storage_.absl::inlined_vector_internal::Storage<absl::cord_internal::CordRep*, 2, std::allocator<absl::cord_internal::CordRep*> >::data_.absl::inlined_vector_internal::Storage<absl::cord_internal::CordRep*, 2, std::allocator<absl::cord_internal::CordRep*> >::Data::allocated.absl::inlined_vector_internal::Storage<absl::cord_internal::CordRep*, 2, std::allocator<absl::cord_internal::CordRep*> >::Allocated::allocated_capacity’ may be used uninitialized [-Werror=maybe-uninitialized]
  360 |     return data_.allocated.allocated_capacity;
      |                            ^~~~~~~~~~~~~~~~~~
/root/workspace/tmp/bld/_deps/abseil-src/absl/strings/cord.cc: In function ‘bool absl::VerifyNode(absl::cord_internal::CordRep*, absl::cord_internal::CordRep*, bool)’:
/root/workspace/tmp/bld/_deps/abseil-src/absl/strings/cord.cc:1274:36: note: ‘worklist’ declared here
 1274 |   absl::InlinedVector<CordRep*, 2> worklist;
      |                                    ^~~~~~~~

[GOGOYAO]

Exactly, the error is a warning. But I use -Werror, so it failed to compile.

[derekmauro]

Reproduction instructions need to include the compiler version and operating system. Please provide this information.

-Werror is unsupported. You should only compile your own code with -Werror. We have a CMake option ABSL_USE_SYSTEM_INCLUDES for this.

We should fix this though. Please let us know the exact version of the tools used.

[GOGOYAO]

Reproduction instructions need to include the compiler version and operating system. Please provide this information.

-Werror is unsupported. You should only compile your own code with -Werror. We have a CMake option ABSL_USE_SYSTEM_INCLUDES for this.

We should fix this though. Please let us know the exact version of the tools used.

cmake: 3.20.2 GCC: 11.2.1 Linux OS: CentOS Linux release 7.9.2009 (Core) LInux Kernel: Linux ost 5.10.104-linuxkit #1 SMP Thu Mar 17 17:08:06 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

[GOGOYAO]

-Werror is unsupported.

Maybe it is better to support Werror, isn't it?

[derekmauro]

Maybe it is better to support Werror, isn't it?

Supporting -Werror means we have to support whatever arbitrary set of warnings people decide to enable, even bad or buggy warnings. It's fine to compile your own code with -Werror if you want, but don't force -Werror on your dependencies. So no, we will never support -Werror.

[GOGOYAO]

Maybe it is better to support Werror, isn't it?

Supporting -Werror means we have to support whatever arbitrary set of warnings people decide to enable, even bad or buggy warnings. It's fine to compile your own code with -Werror if you want, but don't force -Werror on your dependencies. So no, we will never support -Werror.

Get it

[GOGOYAO]

Any more questions to merge this code? @derekmauro