using assigning an array with fgetc() return-CodePudding

I am trying to store the first 4 chars of a .awv file using the fgetc function this is what I have

FILE* WAVF = fopen(FName, "rb");
    std::vector<std::string> ID;
    ID[4];
    for (int i = 0; i < 4; i  )
    {
        ID[i] = fgetc(WAVF);
    }

I keep getting this error however :

Exception thrown at 0x00007FF696431309 in ConsoleApplication3.exe: 0xC0000005: Access violation writing location 0x0000000000000010.

CodePudding user response：

Your program has undefined behavior!

Your vector ID is empty. By calling operator[] on an empty std::vector, invoking an undefined behavior. You got lucky that your program got crashed, saying "Access violation".

You need instead:

// create a vector of string and initialize 4 empty strings
std::vector<std::string> ID(4); 

for (auto& element: ID)
{
    element = some `std::string`s
}

However, in your case, std::fgetc returns intger as

The obtained character on success or EOF on failure.

So you might want the data structures such as std::vector<char> or (at best) std::string.