Compiler warning on comment?

[John Z]

Here is one to consider:
I get this warning on compile in Pelles version 10 ... yes I know upgrade soon! 
-
C:\Program Files\PellesC\Files\vCardz\vCardz\search.c(1006): warning #1044: Trigraph '??!' converted to '|'.


due to this source line

Code Select Expand

             { startrec = 0;} // back to the start (what about loop when doing directory??!!)

I would not think the compiler would care what is in a comment... even though Level 2 and C11

Smallest program is not included since you can just paste the comment.  BUT if that doesn't work I'll post.

John Z

[frankie]

Hello John,
this behavior is fully compliant with the standard, apart the warning that is just informational to advice you that a trigraph has been found and translated.
The C standards, from C89 up to C20, specify the the first phase of a 'unit translation' (read source file compilation), is the mapping of source file to source character set and the translations of trigraphs.
From C17 standard draft:

5.1.1.2 Translation phases
.1 The precedence among the syntax rules of translation is specified by the following phases.
    1. Physical source file multibyte characters are mapped, in an implementation-defined manner, to
        the source character set (introducing new-line characters for end-of-line indicators) if necessary.
       Trigraph sequences are replaced by corresponding single-character internal representations.
    2. Each instance of a backslash character (\) immediately followed by a new-line character is
        deleted, splicing physical source lines (... omissis ...)

So in the very first phase trigraphs are translated to the internal representation, and a warning showed for each of them. This happens before the comment is stripped out from translation process.

[John Z]

Thanks for the great explanation, especially the

This happens before the comment is stripped out from translation process

Got it!

Thank you,
John Z

[frankie]

Anyway I have to admit that the warning is very annoying!   

[Grincheux]

From Pelle's help file:

C trigraph sequences 
All occurrences in a source file of the following sequences of three characters (called trigraph sequences) are replaced with the corresponding single character. They are meant for computers with limited character sets.

Trigraph	Character
??=	#
??(	[
??/	\
??)	]
??'	^
??<	{
??!	|
??>	}
??-	~