StringBuilder out of memory

Question

I'm trying to crash-test my parser with the following string:

var theWholeUTF8 = new StringBuilder();
for (char code = Char.MinValue; code <= Char.MaxValue; code++)
{
        theWholeUTF8.Append(code);
}

However, the test crashes itself while building the string and throws OutOfMemoryException. What am I missing?

Answer 1

The problem is tha code overflows and returns to 0 after being Char.MaxValue. The for cycle then doesn't end.

Try

var theWholeUTF8 = new StringBuilder();

for (int code = Char.MinValue; code <= Char.MaxValue; code++)
{
    theWholeUTF8.Append((char)code);
}

To make it clear... At a certain point

code = Char.MaxValue - 1

code++; // code == Char.MaxValue
is code <= Char.MaxValue? Yes
theWholeUTF8.Append((char)code);

code++; // code == 0
is code <= Char.MaxValue? Yes
theWholeUTF8.Append((char)code);

and so on!

One possible solution is to use for the code a bigger variable. Another solution is:

for (char code = Char.MinValue; code < Char.MaxValue; code++)
{
    theWholeUTF8.Append(code);
}

theWholeUTF8.Append(Char.MaxValue);

where we stop when code == Char.MaxValue and we add manually the Char.MaxValue .

Other solution, obtained by moving the check BEFORE the addition:

char code = Char.MinValue;

while (true)
{
    theWholeUTF8.Append(code);

    if (code == Char.MaxValue)
    {
        break;
    }

    code++;
}