C++ Strip non-ASCII Characters from string

Question

Before you get started; yes I know this is a duplicate question and yes I have looked at the posted solutions. My problem is I could not get them to work.

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Answer 1

isprint depends on the locale, so the character in question must be printable in the current locale.

If you want strictly ASCII, check the range for [0..127]. If you want printable ASCII, check the range and isprint.

Answer 2

Solution:

bool invalidChar (char c) 
{  
    return !(c>=0 && c <128);   
} 
void stripUnicode(string & str) 
{ 
    str.erase(remove_if(str.begin(),str.end(), invalidChar), str.end());  
}

EDIT:

For future reference: try using the __isascii, iswascii commands

Answer 3

At least one problem is in your invalidChar function. It should be:

return !isprint( static_cast<unsigned char>( c ) );

Casting a char to an unsigned is likely to give some very, very big values if the char is negative (UNIT_MAX+1 + c). Passing such a value toisprint` is undefined behavior.