Question

我有这个 p。

#include    <iostream>
#include    <string>
int main()
{
    std::string st = ( = +"10");
    std::cout<<st<<"-"<<st.c_str();
    return 0;    
}

你们期望的是哪类产出没有运行?

页: 1

I am running into such problems while using boost::spirit library and passing its output around as c-strings.

Am I missing something? I am using gcc 4.6.1 (ubuntu 10.10).

Answer 1

这是:

 =  + "10"

或许不会做你所期望的事情。它将“增加”(相对而言)“ASCII”价值=“10”字面字面上的“10”点,即缓冲超支,因此援引未经界定的行为。

如果你在val忙下执行你的方案,你很可能会看到你对此表示不满。

相反,试图:

std::string st = "=";
st += "10";

Answer 2

相反:

#include  <iostream>
#include  <string>
int main()
{
    std::string st = ( = +std::string("10"));
    std::cout<<st<<"-"<<st.c_str();
    return 0;
}

Note "10" is a const char* (pointer). Adding to it will increment the pointer using standard integer arithmetic and not concatenate a string.

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