lex_string_ builds comment descriptors with incorrect back-threads

[Gary Dixon]

The lex_string_$lex entrypoint incorrectly sets the comment.Plast pointer to point to the current comment descriptor, rather than to its predecessor. This bug prevents walking backward through the comments found in a lexed input string.

Also, several of the PL/I comments in the lex_string_.pl1 code are either misleading or inadequate. These make the code harder to read/understand.

I suggest the following changes to repair the comment.Plast bug, and enhance the code comments.

cpa [lpn lex_string_.pl1] ==

A580 comment.Pnext -> comment.Plast = comment.Pnext;
Changed by B to:
B580 comment.Pnext -> comment.Plast = Pcomment;

A616 /* and doubled quotes are _\010n_\010o_\010t being retained, copy the quoted */
Changed by B to:
B616 /* and doubled quotes are NOT being retained, copy the quoted */

A804 stmt.Lvalue = min(max_Lvalue, stmt.Lvalue - Lstr);
Changed by B to:
B804 /* Set actual length of prior stmt. */
B805 stmt.Lvalue = min(max_Lvalue, stmt.Lvalue - Lstr);
B806 /* If prior statement ended on current line, increment the */
B807 /* statement-in-line counter (to be used in new stmt). */

Inserted in B:
B812
Preceding:
A809 stmt.Pnext = allocate (Parea, size(stmt));

A842 /* If a used token already exists, reuse it. */
Changed by B to:
B846 /* If just-prior token was "unmade", reuse the token descriptor. */

Inserted in B:
B863 /* Allocate a new token descriptor. */
Preceding:
A859 if APtoken = null then do;

Comparison finished: 6 differences, 13 lines.