清除矢量列表后，我收到了分段错误 [英] I'm getting a Segmentation fault after I clear a vector list
问题描述
大家好。
我有分段故障问题。底部的代码部分
在第二次进入IF块时为
继续抛出Segmentation故障。
const int WORDS_PER_LINE = 4;
当counter == 7时，字符串连接在IF
块内失败。
但是，奇怪的部分是如果不清除列表（// list.clear（））
它有效......但我害怕我当我没有释放内存时，
为向量重新分配不同的字符串。
代码片段
----- -------------------------------------------------- --------------------------------
while（str！= NULL ）
{
index = counter％WORDS_PER_LINE;
list [index] = * str;
cout<< " I：" << index<< " C：" <<计数器<< "字： << * str<< endl;
if（index ==（WORDS_PER_LINE-1））
{
string ref =
string（" INSERT INTO BANKING（DATE，TRANS_TYPE，AMOUNT，BALANCE）
VALUES（TO_DATE（''"）+
list [0] +
string（"''，''MM / DD / YYYY''），''"）+
list [1] +
string（"''，"）+
list [2] +
string（"，"）+
list [3] +
string（"）;"）;
cout<< 处理...... << ref<< endl;
list.clear（）;
}
counter ++;
delete（str）;
str = parser.readField（）;
}
" fudmore" <福***** @ mindspring.com>写道...我有一个Segmentation fault问题。底部的代码部分在第二次进入IF块时不断抛出Segmentation故障。
const int WORDS_PER_LINE = 4;
当counter == 7时，字符串连接在IF
块中失败。
但是，奇怪的部分是如果不清除列表（//列表。 clear（））
它的工作原理......但是当我向矢量重新分配不同的字符串时，我恐怕不会释放记忆。
什么''列表"在你的程序中？
Code Snippet
---------------------------- ----------------------------------------------
-------------
while（str！= NULL）
{
index = counter％WORDS_PER_LINE;
list [index] = * str ;
cout<< " I：" << index<< " C：" <<计数器<< "字： << * str<< endl;
if（index ==（WORDS_PER_LINE-1））
{
string ref =
string（" INSERT INTO BANKING（DATE） ，TRANS_TYPE，AMOUNT，BALANCE）
VALUES（TO_DATE（''"）+
list [0] +
string（"''，''MM / DD / YYYY'' ），''"）+
list [1] +
string（&'''，"）+
list [2] +
string（"， "）+
list [3] +
string（"）;"）;
cout<< 处理...... << ref<< endl;
list.clear（）;
为什么要在这里清除它？什么是清算的目的？
}
计数器++;
删除（str）;
str = parser.readField（）;
}
我想''list.clear（）''没有用，因为''list''是
修复为包含4个字符串。
调用''list.clear（）''，''list''的大小更改为0，
然后''list [index]''将生成错误（索引超出范围）。
因为''WORDS_PER_LINE''是一个常量，也许可以使用C数组。
std :: string args [WORDS_PER_LINE];
" fudmore" <福***** @ mindspring.com>写了...抱歉没有提到，但列表是
vector< string> list（WORDS_PER_LINE）;
所以，你得到了答案吗？当您定义列表时像这样，
它包含''WORDS_PER_LINE''元素开头。一旦你清除了它，就没有更多的元素了，你不能再使用operator []来引用任何
，直到你调整向量的大小。 br />
因此，解决方案不是清除它。简单。
Victor
Victor Bazarov写道：" fudmore" <福***** @ mindspring.com>写道......
我有一个Segmentation fault问题。底部的代码部分在第二次进入IF块时不断抛出Segmentation故障。
const int WORDS_PER_LINE = 4;
当counter == 7时，字符串连接在IF
块中失败。
但是，奇怪的部分是如果不清除列表（//列表。 clear（））
它的工作原理......但是当我向矢量重新分配不同的字符串时，我恐怕不会释放记忆。
什么是'列表'？在你的程序中？
代码片段
-------------------------------------------------- ------------------------
-------------
< blockquote class =post_quotes> while（str！= NULL）
{
index = counter％WORDS_PER_LINE;
list [index] = * str;
cout << " I：" << index<< " C：" <<计数器<< "字： << * str<< endl;
if（index ==（WORDS_PER_LINE-1））
{
string ref =
string（" INSERT INTO BANKING（DATE） ，TRANS_TYPE，AMOUNT，BALANCE）
VALUES（TO_DATE（''"）+
list [0] +
string（"''，''MM / DD / YYYY'' ），''"）+
list [1] +
string（&'''，"）+
list [2] +
string（"， "）+
list [3] +
string（"）;"）;
cout<< 处理...... << ref<< endl;
list.clear（）;
为什么要在这里清除它？什么是清算的目的？
}
计数器++;
删除（str）;
str = parser.readField（）;
}
Hello Everybody.
I have a Segmentation fault problem. The code section at the bottom
keeps throwing a Segmentation fault when it enters the IF block for the
second time.
const int WORDS_PER_LINE = 4;
when counter == 7 is when the string Concatenation fails within the IF
block.
BUT, the strange part is if the don''t CLEAR the list ( // list.clear())
it works... but i''m afraid that I''m not freeing up memory when i
reassign different strings to the vector.
Code Snippet
---------------------------------------------------------------------------------------
while(str != NULL)
{
index = counter % WORDS_PER_LINE;
list[index] = *str;
cout << "i:" << index << " c:" << counter << " word : " << *str << endl;
if(index == (WORDS_PER_LINE-1))
{
string ref =
string("INSERT INTO BANKING(DATE,TRANS_TYPE,AMOUNT,BALANCE)
VALUES(TO_DATE(''") +
list[0] +
string("'',''MM/DD/YYYY''),''") +
list[1] +
string("'',") +
list[2] +
string(",") +
list[3]+
string(");");
cout << "processing .." << ref << endl;
list.clear();
}
counter++;
delete (str);
str = parser.readField();
}
"fudmore" <fu*****@mindspring.com> wrote...I have a Segmentation fault problem. The code section at the bottom
keeps throwing a Segmentation fault when it enters the IF block for the
second time.
const int WORDS_PER_LINE = 4;
when counter == 7 is when the string Concatenation fails within the IF
block.
BUT, the strange part is if the don''t CLEAR the list ( // list.clear())
it works... but i''m afraid that I''m not freeing up memory when i
reassign different strings to the vector.
What''s "list" in your program?
Code Snippet
-------------------------------------------------------------------------- -------------
while(str != NULL)
{
index = counter % WORDS_PER_LINE;
list[index] = *str;
cout << "i:" << index << " c:" << counter << " word : " << *str << endl;
if(index == (WORDS_PER_LINE-1))
{
string ref =
string("INSERT INTO BANKING(DATE,TRANS_TYPE,AMOUNT,BALANCE)
VALUES(TO_DATE(''") +
list[0] +
string("'',''MM/DD/YYYY''),''") +
list[1] +
string("'',") +
list[2] +
string(",") +
list[3]+
string(");");
cout << "processing .." << ref << endl;
list.clear();
Why do you want to clear it here? What''s the purpose of clearing?
}
counter++;
delete (str);
str = parser.readField();
}
i guess there has no use for ''list.clear()'', because ''list'' is
fixed to hold 4 strings in it.
after you invoke ''list.clear()'', the size of ''list'' change to 0,
then ''list[index]'' would generate an error(index out of range).
Since ''WORDS_PER_LINE'' is a const, maybe C arrays can be used.
std::string args[WORDS_PER_LINE];
"fudmore" <fu*****@mindspring.com> wrote...sorry for not mentioning that but list is
vector <string>list(WORDS_PER_LINE);
So, did you get your answer? When you define your "list" like this,
it contains ''WORDS_PER_LINE'' elements to begin with. As soon as you
clear it, there are no more elements, and you cannot refer to any of
them using operator[] any longer until you resize the vector.
So, the solution is not to clear it. Simple.
Victor
Victor Bazarov wrote:"fudmore" <fu*****@mindspring.com> wrote...I have a Segmentation fault problem. The code section at the bottom
keeps throwing a Segmentation fault when it enters the IF block for the
second time.
const int WORDS_PER_LINE = 4;
when counter == 7 is when the string Concatenation fails within the IF
block.
BUT, the strange part is if the don''t CLEAR the list ( // list.clear())
it works... but i''m afraid that I''m not freeing up memory when i
reassign different strings to the vector.
What''s "list" in your program?
Code Snippet
--------------------------------------------------------------------------
-------------while(str != NULL)
{
index = counter % WORDS_PER_LINE;
list[index] = *str;
cout << "i:" << index << " c:" << counter << " word : " << *str << endl;
if(index == (WORDS_PER_LINE-1))
{
string ref =
string("INSERT INTO BANKING(DATE,TRANS_TYPE,AMOUNT,BALANCE)
VALUES(TO_DATE(''") +
list[0] +
string("'',''MM/DD/YYYY''),''") +
list[1] +
string("'',") +
list[2] +
string(",") +
list[3]+
string(");");
cout << "processing .." << ref << endl;
list.clear();
Why do you want to clear it here? What''s the purpose of clearing?}
counter++;
delete (str);
str = parser.readField();
}
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