error when crlf appears in format expression's control-string

[David Wang]

When compiling a format expression that contains a tilde "~" followed by a CRLF line-ending, the compiler will catch an error stating the character 'Return' is an unknown directive. For example: (this text-entry field may not faithfully reproduce CRLF line endings, but a CRLF line-ending is critical to produce this error).

(format t "Hello ~
World")

Results in the error:
; caught ERROR:
; during macroexpansion of
; (FORMATTER "Hello ~

; World").
; Use *BREAK-ON-SIGNALS* to intercept.
;
; error in FORMAT: unknown directive (character: Return)

The correct behavior occurs when only the LF (unix-style newline line-ending) appears The directive indicator (~) right before the end of the line in the control-string ("Hello ~ World") acts to suppress the newline in the formatted output, and allows the control-string to be typed across multiple-lines.

This bug will primary occur on SBCL on windows, where CRLF line-endings are the standard, but will most likely occur in any SBCL implementation where a CRLF line-ending occurs in a format expression's control string.

Error occurs on:
* Windows SBCL 1.2.1 (32 and 64 bit, downloaded binaries, running on Windows 7 x64)
* Linux SBCL 1.2.1 (32 bit, compiled from source, running on Ubuntu 12.04)

POSSIBLE FIXES:
I have tried to fix this error in the SBCL src code myself, but have had no luck. I believe I have a good solution strategy for this particular error, but my fixes always require using the lisp character expression #\Return, which causes an error when executing "sh make.sh" to build SBCL. I believe this error stems from the fact that #\Return is not a character in the Lisp-standard-ASCII, and thus the compiler will not accept it as Lisp code.

Both of the fixes I have tried are modifications to "late-format.lisp". Each fix I tried is stand-alone, and does not depend on the other:
* One possible fix involves modifying the function "parse-directive", so there is an additional conditional statement that catches CRLF style line-endings and replaces them with LF style line-endings. This may work alright for this bug, but I believe it may cause other bugs in the strict interpretation of other directives such as "@", where the character immediately following "@" is supposed to be included in the output of format (i.e. "@#\Return#\Newline" should technically force the inclusion of #\Return in the output of format).
* Another possible fix involves the addition of a new format-directive, via the macro:
(def-complex-format-directive #\return (colonp atsignp params directives) ... )

Note: I believe characters such as #\Return are considered semi-standard in the CL spec, and so there is grounds for the SBCL compiler to accept them.

OTHER BUGS:
* This bug may be related to SBCL Bug "#310185 wanted: newline policies in external formats". But, I was unsure what the term "external formats" meant, so I created a new, more specific report.
* This bug was reported to cause issues in the use of another lisp library: https://github.com/tpapp/lla/issues/15