Re: gcc 2.95.1 fixes for backslashes in #line, #include

[seebs at plethora dot net]

In message <199908240134.SAA03977@shade.twinsun.com>, Paul Eggert writes:
>  The last quoted sentence is incorrect, because the ANSI standard says
>  only that the behavior of backslashes in file names is defined by
>  the implementation.

Actually, it's worse than that; it's flat out undefined.  :)

>(Also, this change simplifies the code, so it must be right. :-)

A laudable sentiment.  Perhaps it is worth documenting, BTW, that there
are no systems on which you need <foo\bar.h> to process header names?
On NT/'98/etc., <foo/bar.h> will do the same thing.

>+  printf ("  -fbs-filenames	       \\ is ordinary in #include \"...\"\n");

Hmm.  And also, if I read this correctly, in #line; is there a good end-user
friendly way to describe all #-directives-which-take-file-names?

>+	    if (*fend == '\\' && !bs_filenames) {
>+	      char *finc = (char *) fin - 1;
>+	      if (*fin == '\"' && pedantic)
>+		pedwarn ("file name contains \"");

Hmm.  Two points:

1.  You refer to this as "warn only in -pedantic", but I was told that pedwarn
is more like
	if (pedantic)
		error(foo)
	else
		warn(foo)
?

2.  Hmm.  Actually, this is probably not a point; merely pointing out that
" in ""-names isn't allowed by the grammar, whereas " in <>-names is merely
undefined.

>+	  if (pedantic)
>+	    pedwarn ("concatenated string literals in #include");

I would probably warn anyway - I cannot imagine anyone *meaning* to
concatenate string literals in a #include directive.  :)

>[...]This is an extension to the ANSI standard,
>+which prohibits prohibits quotes in @var{file}, and which says that
>+backslashes have implementation-defined behavior.  [...]

s/implementation-defined/undefined/

>+containing a newline, a backslash, and a quote.  This extends ANSI C,
>+which prohibits quotes in @var{file}, and which says that backslashes
>+have implementation-defined behavior.

&

I will say, this definitely looks like an improvement; it's fairly
readable, and it probably does the least surprising thing for most people.

-s