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V811. Decreased performance. Excessive type casting: string -> char * -> string.
The analyzer has detected a code that can be optimized: the code contains an excessive operation when a 'std::string' object is created, and we can eliminate this.
We use the 'c_str()' function to take a pointer to a character array from the 'std::string' object. Then we construct a new object of the 'std::string' type from these characters. For instance, it can happen if the non-optimal expression is:
- a function call argument;
- an assignment operation operand;
- a 'return' operation operand.
Here is a sample for the case with a function call:
void foo(const std::string &s)
{
....
}
....
void bar()
{
std::string str;
....
foo(str.c_str());
}The code is very easy to improve: you just need to remove the call of the 'c_str()' method:
....
void bar()
{
std::string str;
....
foo(str);
}This is a sample of incorrect code for the case with an assignment operator:
std::string str;
....
std::string s = str.c_str();And this is an incorrect code for the 'return' operator:
std::string foo(const std::string &str)
{
....
return str.c_str();
}The errors in the last two cases are fixed in the same way as with the function call.
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