Question

我有这个代码用于填充表格，但我一直收到分段错误。我在我的智慧结束时试图找出错误可能是什么。我的函数接收2个映射并遍历它们以找到公共字符串。它接受这些公共字符串的int值，并将其放在一个表中，以计算常见字符串的次数。

myMap findTable(mapGraph * dbgraph1, mapGraph * dbgraph2)
{
typedef mapGraph::const_iterator iter;
typedef myMap::const_iterator mapiter;

iter it1 = dbgraph1->begin();
iter it2 = dbgraph2->begin();
int count =0;
myMap * newTable = NULL;

//iterating through the 2 samples of dbgraphs
while (it1 != dbgraph1->end() && it2 != dbgraph2->end())
{
    //a match is found for 2 strings
    if (it1->first == it2->first)
    {
        //the component ids of first sample
        int compdb1 = it1->second->comp;

        //the component ids of second sample
        int compdb2 = it2->second->comp;

        //inserting the component ids and counts in the map
        newTable->insert(make_pair(make_pair(compdb1, compdb2), count));
        count++;

        for (mapiter it = newTable->begin(); it != newTable->end(); it++)
        {
            printf("%i %i\t %i\n", it->first.first, it->first.second, it->second);
        }

        it1++;
        it2++;

    }

    //match not found
    else
        it1++;
        it2++;

}
printf("\nCLEAR\n");
return newTable;
}

这是错误：

Address 0x10 is not stack'd, malloc'd or (recently) free'd
Invalid read of size 8
Process terminating with default action of signal 11 (SIGSEGV)
Access not within mapped region at address 0x10

Answer 1

newTable是NULL：

myMap * newTable = NULL;

并且以前从未分配给有效对象：

newTable->insert(make_pair(make_pair(compdb1, compdb2), count));

取消引用NULL指针是未定义的行为。动态地为myMap分配newTable个实例：

myMap* newTable = new myMap(); // Remember to delete later.

或使用堆栈分配的实例：

myMap newTable;

这是一个错误：

//match not found
    else
        it1++;
        it2++;

导致it2在循环的每次迭代中递增，并导致在++迭代器上调用end()。改为：

//match not found
    else
    {
        it1++;
        it2++;
    }

或者为了简化代码，只需在循环中的一个位置递增迭代器，因为它们总是递增（在if\else的每个分支中）。

使用valgrind的地图中的读取大小错误无效

1 个答案: