Question

当我尝试使用原子的is_lock_free（）方法时，我遇到了以下编译错误。

struct Simple1 { int i; };
struct Simple2 { int a; int b; };
struct Simple3 { int a; int b; int c; };

int main()
{
    atomic< Counter > counter;
    atomic< Param > param;
    atomic< Simple1 > s1;
    atomic< Simple2 > s2;
    atomic< Simple3 > s3;

    cout
        << "Is s1 lock free? " << boolalpha << s1.is_lock_free() << '\n'
        << "Is s2 lock free? " << boolalpha << s2.is_lock_free() << '\n'
        << "Is s3 lock free? " << boolalpha << s3.is_lock_free() << '\n';
   }

s1.is_lock_free() and s2.is_lock_free()没问题，atomic< builtin >::is_lock_free()，其中builtin是基本类型，效果很好。

但是对于s3，is_lock_free的调用会产生链接错误：undefined reference to __atomic_is_lock_free

我是否需要链接一些外部库？我该怎么办？

编辑1

在Ubuntu 13.04上的gcc4.8.1上也出现了同样的问题

命令行选项如下：

g++ -O0 -g3 -Wall -c -fmessage-length=0 -std=c++11 -o "atomic_test.o" "atomic_test.cpp" 
g++ -std=c++11 -o hello.exe atomic_test.o

编辑2

我在gcc上添加了-latomic和-lpthread，但我遇到了同样的错误：

04:09:37: Running steps for project atomic...
04:09:37: Configuration unchanged, skipping qmake step.
04:09:37: Starting: "/usr/bin/make" 
/home/dmdtek/Qt/5.1.0/gcc_64/bin/qmake -spec linux-g++ CONFIG+=debug      CONFIG+=declarative_debug CONFIG+=qml_debug -o Makefile ../atomic/atomic.pro
g++ -latomic -lpthread -Wl,-rpath,/home/dmdtek/Qt/5.1.0/gcc_64 -o atomic main.o    
main.o: In function `std::atomic<Simple3>::is_lock_free() const':
/usr/include/c++/4.8/atomic:191: undefined reference to `__atomic_is_lock_free'
main.o: In function `std::atomic<long double>::is_lock_free() const':
/usr/include/c++/4.8/atomic:191: undefined reference to `__atomic_is_lock_free'
collect2: error: ld returned 1 exit status
make: *** [atomic] Error 1
04:09:37: The process "/usr/bin/make" exited with code 2.
Error while building/deploying project atomic (kit: Desktop Qt 5.1.0 GCC 64bit)
When executing step 'Make'
04:09:37: Elapsed time: 00:00.

我的系统上存在libatomic：

$ ldconfig -v | grep atomic
/sbin/ldconfig.real: Path `/lib/x86_64-linux-gnu' given more than once
/sbin/ldconfig.real: Path `/usr/lib/x86_64-linux-gnu' given more than once
libatomic.so.1 -> libatomic.so.1.0.0
/sbin/ldconfig.real: Can't create temporary cache file /etc/ld.so.cache~: Permission denied

Answer 1

您需要链接libatomic（由GCC提供）：

g++ -std=c++11 -o hello.exe atomic_test.o -latomic

mingw-4.8.1原子问题

1 个答案: