Defective case diddling in PATHNAME-DIRECTORY breaks round-tripping.

[Richard M Kreuter]

Defective case diddling in PATHNAME-DIRECTORY breaks round-tripping.

Two problems in SB-IMPL::MAYBE-DIDDLE-CASE's recursion break round-tripping values obtained from a directory when using :COMMON case:

1. PATHNAME-DIRECTORY with case :COMMON does not convert lettercase when there is any lettercase variation in all characters in the directory, but MAKE-PATHNAME with case :COMMON handles the lettercase of each directory element individually:

--
$ sh ./run-sbcl.sh --no-userinit --no-sysinit
(running SBCL from: .)
This is SBCL 1.4.2.276-0288458, an implementation of ANSI Common Lisp.
More information about SBCL is available at <http://www.sbcl.org/>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses. See the CREDITS and COPYING files in the
distribution for more information.
* (pathname-directory "/AB/cd/" :case :common)

(:ABSOLUTE "AB" "cd")
* (make-pathname :case :common :directory (pathname-directory "/AB/cd/" :case :common))

#P"/ab/CD/"
* (pathname-directory #P"/Ab/cd/EF/" :case :common)

(:ABSOLUTE "Ab" "cd" "EF")
* (make-pathname :directory (pathname-directory "/Ab/cd/EF/" :case :common) :case :common)

#P"/Ab/CD/ef/"
--

2. PATHNAME-DIRECTORY doesn't diddle lettercase inside SB-IMPL::PATTERN instances, but MAKE-PATHNAME does:

--
* (pathname-directory "/a*b/" :case :common)

(:ABSOLUTE #<SB-IMPL::PATTERN "a" :MULTI-CHAR-WILD "b">)
* (make-pathname :case :common :directory (pathname-directory "/a*b/" :case :common))

#P"/A*B/"
--

In the above scenarios, I expected round-tripping when using the same values for CASE.

ANSI is ambiguous-by-omission on the details here, but I'd say that PATHNAME-DIRECTORY, and not MAKE-PATHNAME, is the one with the defect, because having PATHNAME-DIRECTORY convert lettercase element-by-element and inside PATTERN instances makes each element of the returned list denote suitably when supplied as other pathname fields to the constructor with :COMMON case, i.e., you can use elements of the list in functions like

(lambda (x) (make-pathname :case :common :name x))

and have a consistent denotation.

The attached patch changes changes SB-IMPL::MAYBE-DIDDLE-CASE to achieve the desired effect.

Other requested info:

--
* $ uname -a
Darwin m5.localdomain 14.5.0 Darwin Kernel Version 14.5.0: Wed Jul 29 02:26:53 PDT 2015; root:xnu-2782.40.9~1/RELEASE_X86_64 x86_64

* *features*

(:64-BIT :64-BIT-REGISTERS :ALIEN-CALLBACKS :ANSI-CL :ASH-RIGHT-VOPS :BSD
 :C-STACK-IS-CONTROL-STACK :COMMON-LISP :COMPACT-INSTANCE-HEADER
 :COMPARE-AND-SWAP-VOPS :COMPLEX-FLOAT-VOPS :CYCLE-COUNTER :DARWIN
 :DARWIN9-OR-BETTER :FLOAT-EQL-VOPS :FP-AND-PC-STANDARD-SAVE :GENCGC
 :IEEE-FLOATING-POINT :IMMOBILE-CODE :IMMOBILE-SPACE :INLINE-CONSTANTS :INODE64
 :INTEGER-EQL-VOP :LINKAGE-TABLE :LITTLE-ENDIAN :MACH-EXCEPTION-HANDLER :MACH-O
 :MEMORY-BARRIER-VOPS :MULTIPLY-HIGH-VOPS :OS-PROVIDES-BLKSIZE-T
 :OS-PROVIDES-DLADDR :OS-PROVIDES-DLOPEN :OS-PROVIDES-PUTWC
 :OS-PROVIDES-SUSECONDS-T :PACKAGE-LOCAL-NICKNAMES :PRECISE-ARG-COUNT-ERROR
 :RAW-INSTANCE-INIT-VOPS :RAW-SIGNED-WORD :RELOCATABLE-HEAP :SB-DOC :SB-EVAL
 :SB-LDB :SB-PACKAGE-LOCKS :SB-SIMD-PACK :SB-SOURCE-LOCATIONS :SB-THREAD
 :SB-UNICODE :SBCL :STACK-ALLOCATABLE-CLOSURES :STACK-ALLOCATABLE-FIXED-OBJECTS
 :STACK-ALLOCATABLE-LISTS :STACK-ALLOCATABLE-VECTORS
 :STACK-GROWS-DOWNWARD-NOT-UPWARD :SYMBOL-INFO-VOPS :UD2-BREAKPOINTS
 :UNBIND-N-VOP :UNDEFINED-FUN-RESTARTS :UNIX :UNWIND-TO-FRAME-AND-CALL-VOP
 :X86-64)

--

[Richard M Kreuter (kreuter)]

Whoops, this proves to be a duplicate of https://bugs.launchpad.net/sbcl/+bug/695486

Sorry for the noise.

[Jan Moringen (scymtym)]

in 1af24465b37ab8ca3dee3f029a16b84092e0ffa0