strings: bugfix: broken inequality comparisons.

Inequality comparisons of strings and symbols are broken due
to assuming that cmp_str returns -1 or 1. cmp_str uses the C
library function wscsmp, and is exposed as the Lisp function
cmp-str. That is correctly documented as returning a negative
or positive value.  But a few function in lib.c assume
otherwise.

On newer glibc's, at least on x86, it seems that wcscmp
does return 1, 0 or -1 consistently; perhaps the newer
optimized assembly routines are ensuring this. It shows
up on older glibc installations where the C version just
returns the difference between the mismatching characters.

* lib.c (cmp_str): Now returns -1, 0 or 1.

* txr.1: Specify the stronger requirements on the cmp-str
return value, adding a note that older versions conform
to a weaker requirement.

1 files changed, 10 insertions, 4 deletions

diff --git a/txr.1 b/txr.1
index 9875d439..fcccdf43 100644
--- a/txr.1
+++ b/txr.1
@@ -23695,12 +23695,12 @@ that length.
 .desc
 The
 .code cmp-str
-function returns a negative integer if
+function returns -1 if
 .meta left-string
 is lexicographically prior to
-.metn right-string ,
-and a positive integer
-if the reverse situation is the case. Otherwise the strings are equal
+.metn right-string .
+If the reverse relationship holds, it returns 1.
+Otherwise the strings are equal
 and zero is returned.
 
 If either or both of the strings are lazy, then they are only forced to the
@@ -23712,6 +23712,12 @@ The lexicographic ordering is naive, based on the character code point
 values in Unicode taken as integers, without regard for locale-specific
 collation orders.
 
+Note: in \*(TX 232 and earlier versions,
+.code cmp-str
+conforms to a weaker requirements: any negative integer value
+may be returned rather than -1, and any positive integer value
+can be returned instead of 1.
+
 .coNP Functions @, str= @, str< @, str> @ str>= and @ str<=
 .synb
 .mets (str= < left-string << right-string )