Recently I came across a bug in Visual Studio 2008 (at least I think it is one).
When I try to create string-literals with two questionmarks followed by another character, something weird occurs: Those three chars are replaced by another char.
Examples:
printf("??-"); --> ~ (hyphen)
printf("??'"); --> ^ (circumflex)
printf("??="); --> # (hash)
printf("??)"); --> ] (square braket)
printf("??("); --> [ (square braket)
printf("??/"); --> \ (backslash)
printf("??!"); --> | (pipe)
printf("??%"); --> ?? (percent sign disappears)
Does anybody know the reason for this replacement?
It's no bug, more a hangover of history. They're C trigraphs - https://msdn.microsoft.com/en-us/library/bt0y4awe.aspx
Di/Tri-graphs are a way to represent characters that weren't easily available back when the language was developed. They let you enter symbols into your source code that you may not have a keyboard key to represent.
Tri-graph Symbol
??= #
??/ \
??' ^
??( [
??) ]
??! |
??< {
??> }
??- ~
The % issue is just the usual one in printf where you need to escape a % with a % if you wish to see it. This is because the % is usually the beginning of a format specifier.