C++删除时内存丢失
C++ valgrind memory loss when deleting?
根据valgrind的说法，我有一些严重的内存泄漏错误。奇怪的是，当我在visual studio运行程序时，它不会崩溃。然而，当我尝试在linux上编译时，我会得到一个segfault，所以我猜是出了问题。
我注释掉了大部分代码，只留下了新的和删除的[]部分（注意，如果没有新的语句，valgrind没有任何问题），但奇怪的是，在这个测试版本中，我确实在删除新的之后的[]/，而valgrind仍然抱怨内存泄漏。
从理论上（据我所知），这不应该是可能的。我只是得到了一个假阳性，还是我忽略了什么？
代码：
void PosApp::loadRecs() {//.......................This function reads all of the perishable/nonperishable data
bool mycontinue = true;
fstream myfile;
myfile.open(_filename, ios::in);
if (!myfile.is_open()) {
myfile.clear();
myfile.close();
myfile.open(_filename, ios::out);
myfile.close();
mycontinue = false;
}
if (mycontinue) {
char buffer = ' '; //Valgrind didn't like it unassigned
int itemindex = 0;
Item* myitem;
while (!myfile.get(buffer).fail()) {// && itemindex <= _noOfItems - 1) {
std::cout << std::endl << "buff: " << buffer << std::endl;
if (buffer == 'N' || buffer == 'P') {
std::cout << std::endl;
std::cout << "The Deallocation:" << std::endl
<< "No of items -1: " << _noOfItems
<< " >= itemindex: " << itemindex << std::endl;
if (_noOfItems - 1 >= itemindex) { //unitialized valgrind error (conditional depends on unitialized values)
std::cout << std::endl << "going to deallocate name: " << _items[itemindex]->name() << " at index: " << itemindex << std::endl;
delete[] _items[itemindex]; //VALGRIND SAY CANT DO THIS invalid read of size 4
}
if (buffer == 'P') {
std::cout << std::endl << "going to allocate a perishable";
myitem = new Perishable();//new keyword
std::cout << std::endl << "DONE allocating a perishable" << std::endl;
delete[] myitem;
}
else if (buffer == 'N') {//else is extra safe
std::cout << std::endl << "going to allocate a nonperishable";
myitem = new NonPerishable();
std::cout << std::endl << "DONE allocating a nonperishable" << std::endl;
delete[] myitem;
}
//std::cout << std::endl << "Going to assign " << " at index: " << itemindex << std::endl;
//myfile.ignore();//.................ignore comma NOTE THIS IS IN WRONG SPOT?
//myitem->load(myfile);
//_items[itemindex] = myitem;
//std::cout << "Assigned name: " << _items[itemindex]->name() << " at index: " << itemindex << std::endl;
//itemindex++; //NoOfItems
}
}
myfile.close();
_noOfItems = itemindex;//inderect lost blocks
}
}
Valgrind输出：
== 20875 == HEAP SUMMARY :
== 20875 == in use at exit : 656 bytes in 5 blocks
== 20875 == total heap usage : 16 allocs, 16 frees, 10, 869 bytes allocated
== 20875 ==
== 20875 == Searching for pointers to 5 not- freed blocks
== 20875 == Checked 101, 796 bytes
== 20875 ==
== 20875 == 656 bytes in 5 blocks are definitely lost in loss record 1 of 1
== 20875 == at 0x4028C39: operator new(unsigned int) (in / usr / lib / valgrind / vgpreload_memcheck - x86 - linux.so)
== 20875 == by 0x804D6BB : sict::PosApp::run() (PosApp.cpp:403)
== 20875 == by 0x804C1A3 : main(milestone4.cpp:8)
== 20875 ==
== 20875 == LEAK SUMMARY :
== 20875 == definitely lost : 656 bytes in 5 blocks
== 20875 == indirectly lost : 0 bytes in 0 blocks
== 20875 == possibly lost : 0 bytes in 0 blocks
== 20875 == still reachable : 0 bytes in 0 blocks
== 20875 == suppressed : 0 bytes in 0 blocks
== 20875 ==
== 20875 == ERROR SUMMARY : 13 errors from 6 contexts(suppressed : 19 from 8)
== 20875 ==
== 20875 == 1 errors in context 1 of 6 :
== 20875 == Conditional jump or move depends on uninitialised value(s)
== 20875 == at 0x4017E9D : strlen(in / lib / ld - 2.14.1.so)
== 20875 == by 0x636F6C2E : ? ? ?
== 20875 == Uninitialised value was created by a stack allocation
== 20875 == at 0x40078F1 : _dl_init_paths(in / lib / ld - 2.14.1.so)
== 20875 ==
== 20875 ==
== 20875 == 1 errors in context 2 of 6 :
== 20875 == Conditional jump or move depends on uninitialised value(s)
== 20875 == at 0x4017E93 : strlen(in / lib / ld - 2.14.1.so)
== 20875 == by 0x636F6C2E : ? ? ?
== 20875 == Uninitialised value was created by a stack allocation
== 20875 == at 0x40078F1 : _dl_init_paths(in / lib / ld - 2.14.1.so)
== 20875 ==
== 20875 ==
== 20875 == 2 errors in context 3 of 6 :
== 20875 == Invalid read of size 4
== 20875 == at 0x804C70D : sict::PosApp::loadRecs() (PosApp.cpp:132)
== 20875 == by 0x804D6BB : sict::PosApp::run() (PosApp.cpp:403)
== 20875 == by 0x804C1A3 : main(milestone4.cpp:8)
== 20875 == Address 0x43021e4 is 4 bytes before a block of size 148 alloc'd
== 20875 == at 0x4028C39 : operator new(unsigned int) (in / usr / lib / valgrind / vgpreload_memcheck - x86 - linux.so)
== 20875 == by 0x804D6BB : sict::PosApp::run() (PosApp.cpp:403)
== 20875 == by 0x804C1A3 : main(milestone4.cpp:8)
== 20875 ==
== 20875 ==
== 20875 == 3 errors in context 4 of 6 :
== 20875 == Invalid read of size 4
== 20875 == at 0x804C7DB : sict::PosApp::loadRecs() (PosApp.cpp:139)
== 20875 == by 0x804D6BB : sict::PosApp::run() (PosApp.cpp:403)
== 20875 == by 0x804C1A3 : main(milestone4.cpp:8)
== 20875 == Address 0x4302ab4 is 4 bytes before a block of size 120 alloc'd
== 20875 == at 0x4028C39 : operator new(unsigned int) (in / usr / lib / valgrind / vgpreload_memcheck - x86 - linux.so)
== 20875 == by 0x804D6BB : sict::PosApp::run() (PosApp.cpp:403)
== 20875 == by 0x804C1A3 : main(milestone4.cpp:8)
== 20875 ==
== 20875 ==
== 20875 == 5 errors in context 5 of 6 :
== 20875 == Invalid free() / delete / delete[]
== 20875 == at 0x4027B13 : operator delete[](void*) (in / usr / lib / valgrind / vgpreload_memcheck - x86 - linux.so)
== 20875 == by 0x804D6BB : sict::PosApp::run() (PosApp.cpp:403)
== 20875 == by 0x804C1A3 : main(milestone4.cpp:8)
== 20875 == Address 0x43021e4 is 4 bytes before a block of size 148 alloc'd
== 20875 == at 0x4028C39 : operator new(unsigned int) (in / usr / lib / valgrind / vgpreload_memcheck - x86 - linux.so)
== 20875 == by 0x804D6BB : sict::PosApp::run() (PosApp.cpp:403)
== 20875 == by 0x804C1A3 : main(milestone4.cpp:8)
== 20875 ==
--20875--
--20875--used_suppression : 19 U1004 - ARM - _dl_relocate_object
== 20875 ==
== 20875 == ERROR SUMMARY : 13 errors from 6 contexts(suppressed : 19 from 8)
new应与delete匹配，new[]应与delete[]匹配。否则就是未定义的行为。您似乎正在对通过new分配的内存执行delete[]。
开始：
myitem = new Perishable();//new keyword
delete[] myitem;
您正在为未分配给new[]的内容调用delete[]。这是不明确的行为，勇敢地抱怨是正确的。
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