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Linux(i686)上的Clang 3.2用于构建以下C 11代码
#include <iostream>
#include <functional>
typedef std::function<void ()> Action;
typedef std::function<int ()> Generator;
Action act(Generator const& gen)
{
return [=]()
{
std::cout << gen() << std::endl;
};
}
int main()
{
static Generator const gen([]() { return 0; });
act(gen);
return 0;
}
用clang test.cpp -std = c 0x&&& valgrind –leak-check = full –log-file = tmp.log.memcheck ./a.out然后我得到
==600== HEAP SUMMARY: ==600== in use at exit: 1 bytes in 1 blocks ==600== total heap usage: 3 allocs,2 frees,18 bytes allocated ==600== ==600== 1 bytes in 1 blocks are definitely lost in loss record 1 of 1 ==600== at 0x402B124: operator new(unsigned int) (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==600== by 0x8048D4F: std::_Function_base::_Base_manager<main::$_1>::_M_clone(std::_Any_data&,std::_Any_data const&,std::integral_constant<bool,false>) (in /home/neuront/a.out) ==600== by 0x8048C21: std::_Function_base::_Base_manager<main::$_1>::_M_manager(std::_Any_data&,std::_Manager_operation) (in /home/neuront/a.out) ==600== by 0x8049455: std::function<int ()>::function(std::function<int ()> const&) (in /home/neuront/a.out) ==600== by 0x8049283: std::function<int ()>::function(std::function<int ()> const&) (in /home/neuront/a.out) ==600== by 0x80489B1: act(std::function<int ()> const&) (in /home/neuront/a.out) ==600== by 0x8048A6C: main (in /home/neuront/a.out) ==600== ==600== LEAK SUMMARY: ==600== definitely lost: 1 bytes in 1 blocks ==600== indirectly lost: 0 bytes in 0 blocks ==600== possibly lost: 0 bytes in 0 blocks ==600== still reachable: 0 bytes in 0 blocks ==600== suppressed: 0 bytes in 0 blocks ==600== ==600== For counts of detected and suppressed errors,rerun with: -v ==600== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
我不知道该代码是否有任何问题(并导致只有一个字节泄漏),但如果使用g 4.7编译,则不会有内存泄漏.有什么建议吗？
解决方法
分配在这里发生：
return [=]()
其中说“捕获不是值的参数”,包括“std :: cout”等,这意味着复制它们.
以下代码通过相同的编译& valgrind检查没有错误,但是请注意,程序员负责确保act的“gen”参数的生命周期长于lambda的生命周期.
#include <iostream>
#include <functional>
typedef std::function<void ()> Action;
typedef std::function<int ()> Generator;
Action act(Generator const& gen)
{
return [&gen]()
{
std::cout << gen() << std::endl;
};
}
int main()
{
static Generator const gen([]() { return 0; });
act(gen);
return 0;
}
