std :: string和char *，我做错了什么？ [英] std::string and char*, what am i doing wrong?
问题描述
我有一个看起来像......的函数。
void函数（std :: string& oldval）
{
int iSome_size = xxx; //得到一些大小
char * tmp = NULL;
tmp = new char [iSome_size + 1];
/ /获取一些文本到tmp
//然后将数据复制到std :: string（...）
oldval = tmp;
删除[] tmp;
tmp = NULL;
}
//但值传递给oldval是错误的，oldval被分配了一些
垃圾。
//我错过了什么？
非常感谢
Sims
" Sims" < SI ********* @ hotmail.com>在留言中写道
news：bu ************ @ ID-162430.news.uni-berlin.de ...你好，
我有一个看起来像......的函数。
void函数（std :: string& oldval）
{
int iSome_size = xxx; //得到一些大小
char * tmp = NULL;
tmp = new char [iSome_size + 1];
//将一些文本输入tmp
你是怎么得到一些文字的？进入临时？尝试使用这样的机制：
std :: strcpy（tmp，" Good"）;
//你将需要inlcude<为c_string>为此
//然后将数据复制到std :: string（...）
oldval = tmp;
delete [] tmp;
tmp = NULL;
}
//但是传递给oldval的值是错误的，oldval被分配了一些垃圾。
//我错过了什么？
非常感谢
模拟人生
问候，
Sumit。
我的功能看起来像......
void Function（std :: string& oldval）
{
int iSome_size = xxx; //得到一些大小
char * tmp = NULL;
tmp = new char [iSome_size + 1];
//将一些文本输入tmp
你是怎么得到一些文字的？进入临时？尝试使用这样的机制：
好吧，我正在使用Window API，
RegQueryValueEx（...并且返回的值是corect。
当我跟踪代码时，我可以看到值很好。
但是一旦我尝试将它复制到我的std :: string它不起作用。
Sims
" Sims" < SI ********* @ hotmail.com>在消息中写道
news：bu ************ @ ID-162430.news.uni-berlin.de ...< blockquote class =post_quotes>
我有一个看起来像......的函数。
void函数（std :: string& oldval）
{
int iSome_size = xxx; //得到一些大小
char * tmp = NULL;
tmp = new char [iSome_size + 1];
//将一些文本输入tmp
你是怎么得到一些文字的？进入临时？尝试使用这样的机制：
好吧，我正在使用Window API，RegQueryValueEx（...），返回的值是corect。
当我跟踪代码时，我可以看到值很好。
但是当我尝试将它复制到我的std :: string时它不起作用。
如何发布整个代码。
可能是你可以用虚拟功能分离Windows API然后尝试
显示代码。
有人可以帮助你。
-Sharad
PS：尝试在调试器下运行代码。
Hi,
I have a function that looks something like ....
void Function( std::string &oldval )
{
int iSome_size = xxx; // get some size
char *tmp = NULL;
tmp = new char[iSome_size+1];
// get some text into the tmp
// and then copy the data to the std::string(...)
oldval = tmp;
delete [] tmp;
tmp = NULL;
}
// but the value passed to oldval is wrong, oldval gets allocated some
garbage.
// what am i missing?
Many thanks
Sims
"Sims" <si*********@hotmail.com> wrote in message
news:bu************@ID-162430.news.uni-berlin.de...Hi,
I have a function that looks something like ....
void Function( std::string &oldval )
{
int iSome_size = xxx; // get some size
char *tmp = NULL;
tmp = new char[iSome_size+1];
// get some text into the tmp
How did you "get some text" into temp? Try to use a mechanism like this:
std::strcpy(tmp,"Good");
// you will need to inlcude <cstring> for this
// and then copy the data to the std::string(...)
oldval = tmp;
delete [] tmp;
tmp = NULL;
}
// but the value passed to oldval is wrong, oldval gets allocated some
garbage.
// what am i missing?
Many thanks
Sims
Regards,
Sumit.
I have a function that looks something like ....
void Function( std::string &oldval )
{
int iSome_size = xxx; // get some size
char *tmp = NULL;
tmp = new char[iSome_size+1];
// get some text into the tmp
How did you "get some text" into temp? Try to use a mechanism like this:
Well, i am using a Window API,
RegQueryValueEx(...) and the value returned is corect.
When i am tracing the code i can see that the value is good.
But as soon as i try to copy it to my std::string it does not work.
Sims
"Sims" <si*********@hotmail.com> wrote in message
news:bu************@ID-162430.news.uni-berlin.de...
I have a function that looks something like ....
void Function( std::string &oldval )
{
int iSome_size = xxx; // get some size
char *tmp = NULL;
tmp = new char[iSome_size+1];
// get some text into the tmp
How did you "get some text" into temp? Try to use a mechanism like this:
Well, i am using a Window API,
RegQueryValueEx(...) and the value returned is corect.
When i am tracing the code i can see that the value is good.
But as soon as i try to copy it to my std::string it does not work.
How about posting the whole code.
May be you can separate out the Windows API with a dummy function and then try
showing the code.
Someone would be then able to help you.
-Sharad
P.S : Try running the code under a debugger.
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