创建一个unique_ptr来保存在免费存储中分配的数组的正确方法是什么?Visual Studio 2013默认情况下支持此功能,但是当我在Ubuntu上使用gcc版本4.8.1时,会出现内存泄漏和未定义的行为。
可以使用以下代码重现该问题:
#include <memory> #include <string.h> using namespace std; int main() { unique_ptr<unsigned char> testData(new unsigned char[16000]()); memset(testData.get(),0x12,0); return 0; }
Valgrind将给出以下输出:
==3894== 1 errors in context 1 of 1: ==3894== Mismatched free() / delete / delete [] ==3894== at 0x4C2BADC: operator delete(void*) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==3894== by 0x400AEF: std::default_delete<unsigned char>::operator()(unsigned char*) const (unique_ptr.h:67) ==3894== by 0x4009D0: std::unique_ptr<unsigned char, std::default_delete<unsigned char> >::~unique_ptr() (unique_ptr.h:184) ==3894== by 0x4007A9: main (test.cpp:19) ==3894== Address 0x5a1a040 is 0 bytes inside a block of size 16,000 alloc'd ==3894== at 0x4C2AFE7: operator new[](unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==3894== by 0x40075F: main (test.cpp:15)
使用T[]专业化:
T[]
std::unique_ptr<unsigned char[]> testData(new unsigned char[16000]());
请注意,在理想情况下,不必显式使用new实例化unique_ptr,从而避免了潜在的异常安全隐患。为此,C ++ 14为您提供了std::make_unique功能模板。有关更多详细信息,请参见此出色的GOTW。语法为:
new
unique_ptr
std::make_unique
auto testData = std::make_unique<unsigned char[]>(16000);