C++ 当我没有'；没有释放任何内存？
下面的代码C++ 当我没有'；没有释放任何内存？,c++,placement-new,dr-memory,C++,Placement New,Dr Memory,下面的代码 #include <vector> #include <string> #include <iostream> struct Type { std::string a; }; int main() { std::vector<unsigned char> data; data.resize(sizeof(Type)); Type* a = new (&data[0]) Type({&quo
#include <vector>
#include <string>
#include <iostream>
struct Type
{
std::string a;
};
int main()
{
std::vector<unsigned char> data;
data.resize(sizeof(Type));
Type* a = new (&data[0]) Type({"something"});
data.resize(sizeof(Type)*2);
Type* b = new (&data[sizeof(Type)]) Type({"else"});
Type* ts = reinterpret_cast<Type*>(&data[0]);
for(std::size_t i = 0; i < 2; ++i)
{
std::cout << ts[i].a << std::endl;
ts[i].~Type();
}
return 0;
}
#包括
#包括
#包括
结构类型
{
std：：字符串a；
};
int main（）
{
std：：矢量数据；
数据。调整大小（sizeof（Type））；
Type*a=new（&data[0]）Type（{“something”}）；
数据。调整大小（sizeof（Type）*2）；
Type*b=新的（&data[sizeof（Type）]）类型（{“else”}）；
类型*ts=重新解释强制转换（&data[0]）；
对于（标准：：尺寸_t i=0；i<2；++i）
{
标准：：cout
当我没有释放任何内存时
当然有。您（可能）在此处释放内存：
问题是，当向量重新分配内存时，它会将无符号字符
元素复制到其他地方。这对在该内存中创建的类型
对象不起作用，因为类型
可复制性不高。为什么a
不是一个指向已调整大小的向量的指针呢？还有，为什么不使用just使用std:：vector
？对一个没有防御能力的vector
@nathan做了多么可怕的事情啊，我没有使用vector
，因为我提供了一个我遇到的问题的最小示例。在任何情况下，我都不会访问Type*a
，所以这不可能是问题。的确，vector内存可能已被释放，但是不清楚（对我来说）这是Dr.Memory报告的问题的原因。请注意，第一个错误发生在fwrite中，可能是访问字符串数据。如果“某物”
保留在字符串中（小字符串优化），则它位于向量内存中，您可能会遇到问题。但如果它不合适，则它位于堆中，并且该内存没有被释放。而Dr. Memory version 2.2.0 build 1 built on Jul 1 2019 00:42:20
Windows version: WinVer=105;Rel=1909;Build=18363;Edition=Enterprise
Dr. Memory results for pid 14664: "CPPTests.exe"
Application cmdline: "bin/Debug/CPPTests.exe -callstack_max_frames 40 -malloc_max_frames 40 -free_max_frames 40"
Recorded 117 suppression(s) from default C:\Program Files (x86)\Dr. Memory\bin\suppress-default.txt
Error #1: UNADDRESSABLE ACCESS of freed memory: reading 0x01750568-0x01750569 1 byte(s)
# 0 msvcrt.dll!_fwrite_nolock
# 1 msvcrt.dll!fwrite
# 2 libstdc++-6.dll!? +0x0 (0x6fe5cf56 <libstdc++-6.dll+0x1cf56>)
# 3 libstdc++-6.dll!? +0x0 (0x6ff23d80 <libstdc++-6.dll+0xe3d80>)
# 4 _fu0___ZSt4cout [C:/tests.cpp:26]
# 5 __tmainCRTStartup [D:/mingwbuild/mingw-w64-crt-git/src/mingw-w64/mingw-w64-crt/crt/crtexe.c:335]
# 6 KERNEL32.dll!BaseThreadInitThunk +0x18 (0x75306359 <KERNEL32.dll+0x16359>)
Note: @0:00:00.608 in thread 3732
Note: next higher malloc: 0x01750598-0x017505c8
Note: prev lower malloc: 0x01750468-0x0175046b
Note: 0x01750568-0x01750569 overlaps memory 0x01750560-0x01750578 that was freed here:
Note: # 0 replace_operator_delete [d:\drmemory_package\common\alloc_replace.c:2975]
Note: # 1 __gnu_cxx::new_allocator<>::deallocate [C:/MSYS2-32/mingw32/include/c++/10.1.0/ext/new_allocator.h:133]
Note: # 2 std::allocator_traits<>::deallocate [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/allocator.h:187]
Note: # 3 std::_Vector_base<>::_M_deallocate [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/stl_vector.h:354]
Note: # 4 std::vector<>::_M_default_append [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/vector.tcc:675]
Note: # 5 std::vector<>::resize [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/stl_vector.h:940]
Note: instruction: movsx (%eax) -> %eax
Error #2: INVALID HEAP ARGUMENT to free 0x01750568
# 0 replace_operator_delete [d:\drmemory_package\common\alloc_replace.c:2975]
# 1 __gnu_cxx::new_allocator<>::deallocate [C:/MSYS2-32/mingw32/include/c++/10.1.0/ext/new_allocator.h:133]
# 2 std::allocator_traits<>::deallocate [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/allocator.h:187]
# 3 std::__cxx11::basic_string<>::_M_destroy [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/basic_string.h:237]
# 4 std::__cxx11::basic_string<>::_M_dispose [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/basic_string.h:232]
# 5 std::__cxx11::basic_string<>::~basic_string [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/basic_string.h:658]
# 6 Type::~Type [C:/tests.cpp:5]
# 7 _fu0___ZSt4cout [C:/tests.cpp:27]
# 8 __tmainCRTStartup [D:/mingwbuild/mingw-w64-crt-git/src/mingw-w64/mingw-w64-crt/crt/crtexe.c:335]
# 9 KERNEL32.dll!BaseThreadInitThunk +0x18 (0x75306359 <KERNEL32.dll+0x16359>)
Note: @0:00:00.743 in thread 3732
Note: next higher malloc: 0x01750598-0x017505c8
Note: prev lower malloc: 0x01750468-0x0175046b
Note: 0x01750568-0x01750568 overlaps memory 0x01750560-0x01750578 that was freed here:
Note: # 0 replace_operator_delete [d:\drmemory_package\common\alloc_replace.c:2975]
Note: # 1 __gnu_cxx::new_allocator<>::deallocate [C:/MSYS2-32/mingw32/include/c++/10.1.0/ext/new_allocator.h:133]
Note: # 2 std::allocator_traits<>::deallocate [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/allocator.h:187]
Note: # 3 std::_Vector_base<>::_M_deallocate [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/stl_vector.h:354]
Note: # 4 std::vector<>::_M_default_append [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/vector.tcc:675]
Note: # 5 std::vector<>::resize [C:/MSYS2-32/mingw32/include/c++/10.1.0/bits/stl_vector.h:940]
===========================================================================
FINAL SUMMARY:
DUPLICATE ERROR COUNTS:
SUPPRESSIONS USED:
ERRORS FOUND:
1 unique, 1 total unaddressable access(es)
0 unique, 0 total uninitialized access(es)
1 unique, 1 total invalid heap argument(s)
0 unique, 0 total GDI usage error(s)
0 unique, 0 total handle leak(s)
0 unique, 0 total warning(s)
0 unique, 0 total, 0 byte(s) of leak(s)
0 unique, 0 total, 0 byte(s) of possible leak(s)
ERRORS IGNORED:
1 potential error(s) (suspected false positives)
(details: C:\AppData\Roaming\Dr. Memory\DrMemory-CPPTests.exe.14664.000\potential_errors.txt)
3 unique, 9 total, 154 byte(s) of still-reachable allocation(s)
(re-run with "-show_reachable" for details)
Details: C:\AppData\Roaming\Dr. Memory\DrMemory-CPPTests.exe.14664.000\results.txt
data.resize(sizeof(Type)*2);
ts[i].~Type();
} // closes main