CVS commit: src/lib/libedit

["Christos Zoulas" <christos%netbsd.org@localhost>]

Module Name:    src
Committed By:   christos
Date:           Thu Jun  2 15:11:18 UTC 2016

Modified Files:
        src/lib/libedit: readline.c

Log Message:
>From Ingo Schwarze:

In libedit, the only way how H_ENTER can fail is memory exhaustion,
too, and of course it is handled gracefully, returning -1 from
history().  So of course, we will continue to handle it gracefully
in add_history() as well, but we are free to decide what to do with
the library state in this case because GNU just dies...

I think the most reasonable course of action is to simply not change
the library state in any way when add_history() fails due to memory
exhaustion, but just return.

If H_ENTER does not fail, we know that the history now contains at
least one entry, so there is no need any longer to check the H_GETSIZE
return value.  And we can of course always set current_history_valid.

While testing these changes, i noticed three problems so closely
related that i'd like to fix them in the same diff.

 1. libedit has the wrong prototype for add_history().
    GNU readline-6.3 defines it as void add_history(const char *).
    Of course, that is very stupid - no way to report problems to
    the caller!  But the whole point of a compatibility mode is
    being compatible, so we should ultimately change this.
    Of course, changing the prototype of a public symbol requires
    a libedit major bump.  I don't want to do that casually.
    Rather, i will take a note and change the prototype the next
    time we need a libedit major bump for more important reasons.
    For now, let's just always return 0.

 2. While *implicitely* pushing an old entry off the history
    increments history_base in GNU readline, testing reveals that
    *explicitly* deleting one does not.  Again, this is not
    documented, but it applies to both remove_history() and
    stifle_history().  So delete history_base manipulation
    from stifle_history(), which also allows to simplify the
    code and delete two automatic variables.

 3. GNU readline add_history(NULL) crashes with a segfault.
    There is nothing wrong with having a public interface
    behave that way.  Many standard interfaces do, including
    strlen(3).  Such crashes can even be useful to catch
    buggy application programs.
    In libedit/readline.c rev. 1.104, Christos made add_history()
    silently ignore this coding error, according to the commit
    message to hide a bug in nslookup(1).  That change was never
    merged to OpenBSD.  I strongly disagree with this change.
    If nslookup(1) is still broken, that program needs to be
    fixed instead.  In any case, delete the bogus check; hiding
    bugs is dangerous.


To generate a diff of this commit:
cvs rdiff -u -r1.134 -r1.135 src/lib/libedit/readline.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.