apache
struct/class that require cacheline alignment may not work when using new (before c++17).
Is your feature request related to a problem? (你需要的功能是否与某个问题有关?) 当前 brpc 代码默认使用的 C++ 标准为 11，不支持 align new (since c++17 https://en.cppreference.com/w/cpp/memory/new/operator_new) .
如果某个 class 指定了 alignment 要求（例如 BAIDU_CACHELINE_ALIGNMENT），代码中使用 new 的方式来分配其对象时，地址有可能并不是严格按照其对齐方式的。
要让一个变量或结构体按cacheline对齐，可以include <butil/macros.h>后使用BAIDU_CACHELINE_ALIGNMENT宏，请自行grep brpc的代码了解用法。
https://github.com/apache/brpc/blob/master/docs/cn/atomic_instructions.md#cacheline
例如以下代码，使用当前的编译选项，就可能会出现错误。
class BAIDU_CACHELINE_ALIGNMENT A {
int i;
};
int main() {
for(size_t i =0 ;i<100;i++) {
A* a = new A();
// maybe fail.
assert((reinterpret_cast<uintptr_t>(a) & (63)) == 0);
}
Describe the solution you'd like (描述你期望的解决方法)
使用 new 来分配指定对齐要求的类时，内存地址应满足对齐的要求。 升级为 C++17 标准，或者开启 -faligned_new （gcc 7.4+，clang 7.1.0+ 都已经支持) .
目前来看是强行关闭了该警告信息（不知道具体原因）. https://github.com/apache/brpc/blob/f3fe5fc4ff315aeed1f1e4b6c43c2ebf470d4381/CMakeLists.txt#L70-L72
Describe alternatives you've considered (描述你想到的折衷方案) 对于需要对齐的类，在使用 new 分配内存时使用 aligned_alloc/posix_memalign 等函数申请 alignment 内存，再使用 Placement new 指定内存空间进行初始化.
Additional context/screenshots (更多上下文/截图) os: 20.04.1-Ubuntu compiler: clang version 10.0.0-4ubuntu1 cpu: x86_64, cache_alignment : 64 byte
例如对于 class BAIDU_CACHELINE_ALIGNMENT/*note*/ Socket 类:
socket 的地址为 0x00005555567f1530, 并不是 64 byte 对齐，违反了要求，可能引起 false-sharing.
没开-faligned-new还用new来动态分配__attribute__((aligned()))标记的类, 真是aligned了个寂寞
是的，这里还有另外一个隐含的问题。 如果 brpc 作为第三方库，编译时未加 -faligned-new， 但项目中使用了其头文件中的声明的某个类（cache line alignment），并且项目编译使用了 aligned_new， 而该类的析构函数（在 brpc 三方库中定义）调用 delete 释放对象空间时也不会调用
void operator delete ( void* ptr, std::size_t sz, std::align_val_t al ) noexcept;
也就是说 new （aligned_new) 和 delete 不匹配，delete 的 size 可能会小于实际 new 的 size （为类对齐要求的 padding)。 这里可能会产生一些问题, 例如一些项目中覆盖了 malloc/free，new/delete 定制化了 allocator，会导致申请和释放的大小不一致。 或者在开启了 ASAN 检查时，会检查出 new/delete 类型不匹配。
=================================================================
==155368==ERROR: AddressSanitizer: new-delete-type-mismatch on 0x621000030d00 in thread T22 (brpc_timer):
object passed to delete has wrong type:
size of the allocated type: 4096 bytes;
size of the deallocated type: 4096 bytes.
alignment of the allocated type: default-aligned;
alignment of the deallocated type: 64 bytes.
#0 0x7ff6e41a35d5 in operator delete(void*, unsigned long, std::align_val_t) (/usr/lib64/libasan.so.5+0x1105d5)
#1 0x752bc9 in bvar::detail::AgentGroup<bvar::detail::AgentCombiner<long, long, bvar::detail::AddTo<long> >::Agent>::_destroy_tls_blocks() external/com_github_apache_brpc/src/bvar/detail/agent_group.h:166
#2 0x752bc9 in bvar::detail::AgentGroup<bvar::detail::AgentCombiner<long, long, bvar::detail::AddTo<long> >::Agent>::_destroy_tls_blocks() external/com_github_apache_brpc/src/bvar/detail/agent_group.h:161
#3 0x150d34f in butil::detail::ThreadExitHelper::~ThreadExitHelper() external/com_github_apache_brpc/src/butil/thread_local.cpp:41
#4 0x150d34f in delete_thread_exit_helper external/com_github_apache_brpc/src/butil/thread_local.cpp:77
#5 0x150d34f in delete_thread_exit_helper external/com_github_apache_brpc/src/butil/thread_local.cpp:76
#6 0x7ff6e3c68ca1 in __nptl_deallocate_tsd /usr/src/debug/glibc-2.17-c758a686/nptl/pthread_create.c:155
#7 0x7ff6e3c68eb2 in start_thread /usr/src/debug/glibc-2.17-c758a686/nptl/pthread_create.c:314
#8 0x7ff6e2690b0c in clone (/lib64/libc.so.6+0xfeb0c)
0x621000030d00 is located 0 bytes inside of 4096-byte region [0x621000030d00,0x621000031d00)
allocated by thread T22 (brpc_timer) here:
#0 0x7ff6e41a1767 in operator new(unsigned long, std::nothrow_t const&) (/usr/lib64/libasan.so.5+0x10e767)
#1 0x1227afe in bvar::detail::AgentGroup<bvar::detail::AgentCombiner<long, long, bvar::detail::AddTo<long> >::Agent>::get_or_create_tls_agent(int) external/com_github_apache_brpc/src/bvar/detail/agent_group.h:150
#2 0x1227afe in bvar::detail::AgentCombiner<long, long, bvar::detail::AddTo<long> >::get_or_create_tls_agent() external/com_github_apache_brpc/src/bvar/detail/combiner.h:297
#3 0x1227afe in bvar::Reducer<long, bvar::detail::AddTo<long>, bvar::detail::MinusFrom<long> >::operator<<(long) external/com_github_apache_brpc/src/bvar/reducer.h:194
#4 0x1227afe in int bthread::TaskGroup::start_background<true>(unsigned long*, bthread_attr_t const*, void* (*)(void*), void*) external/com_github_apache_brpc/src/bthread/task_group.cpp:453
#5 0x11fa28f in bthread::start_from_non_worker(unsigned long*, bthread_attr_t const*, void* (*)(void*), void*) external/com_github_apache_brpc/src/bthread/bthread.cpp:150
#6 0x11fa28f in bthread_start_background external/com_github_apache_brpc/src/bthread/bthread.cpp:230
#7 0xaac90d in braft::RepeatedTimerTask::on_timedout(void*) external/com_meituan_mraft/src/braft/repeated_timer_task.cpp:120
#8 0x1200a04 in bthread::TimerThread::Task::run_and_delete() external/com_github_apache_brpc/src/bthread/timer_thread.cpp:282
#9 0x1202fb5 in bthread::TimerThread::run() external/com_github_apache_brpc/src/bthread/timer_thread.cpp:395
#10 0x12075ef in bthread::TimerThread::run_this(void*) external/com_github_apache_brpc/src/bthread/timer_thread.cpp:122
#11 0x7ff6e3c68ea4 in start_thread /usr/src/debug/glibc-2.17-c758a686/nptl/pthread_create.c:307
I met the same problem. I compile my project in C++17, while the compilation option for BRPC is C++11, so ASAN detects the dismatch between new and delete.
I met the same problem. I compile my project in C++17, while the compilation option for BRPC is C++11, so ASAN detects the dismatch between new and delete.
https://github.com/apache/brpc/pull/2421 Try this fix.
Thx, my current workaround is compiling brpc with std=c++17 too. Just wanna report the unworkable cacheline alignment and underlying risk in mixed compilation units.
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发件人: Dongsheng He @.> 发送时间: Monday, February 26, 2024 10:56:16 PM 收件人: apache/brpc @.> 抄送: Tian @.>; Comment @.> 主题: Re: [apache/brpc] struct/class that require cacheline alignment may not work when using new (before c++17). (Issue #2416)
=================================================================
==155368==ERROR: AddressSanitizer: new-delete-type-mismatch on 0x621000030d00 in thread T22 (brpc_timer):
object passed to delete has wrong type:
size of the allocated type: 4096 bytes;
size of the deallocated type: 4096 bytes.
alignment of the allocated type: default-aligned;
alignment of the deallocated type: 64 bytes.
#0 0x7ff6e41a35d5 in operator delete(void*, unsigned long, std::align_val_t) (/usr/lib64/libasan.so.5+0x1105d5)
#1 0x752bc9 in bvar::detail::AgentGroup<bvar::detail::AgentCombiner<long, long, bvar::detail::AddTo
0x621000030d00 is located 0 bytes inside of 4096-byte region [0x621000030d00,0x621000031d00)
allocated by thread T22 (brpc_timer) here:
#0 0x7ff6e41a1767 in operator new(unsigned long, std::nothrow_t const&) (/usr/lib64/libasan.so.5+0x10e767)
#1 0x1227afe in bvar::detail::AgentGroup<bvar::detail::AgentCombiner<long, long, bvar::detail::AddTo
I met the same problem. I compile my project in C++17, while the compilation option for BRPC is C++11, so ASAN detects the dismatch between new and delete.
#2421https://github.com/apache/brpc/pull/2421 Try this fix.
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