[sword-devel] ListKey issue (bug?)

[Matthew Talbert]

We ran into an interesting issue with ListKeys. The code in question
is used in Xiphos to get a list of search results, then iterate
through them to add to a gui control. I started noticing that
occasionally, an entry would be junk, ie non-printing characters. We
traced it down to this portion of code in Xiphos:

const char *BackEnd::get_next_listkey(void)
{
	const char *retval = NULL;
	
	while(!results.Error()) {
		retval = results.getText();
		results++;
		return retval;
	}
	return NULL;	
}

So with some debug messages, we were able to determine that retval
always got the correct text from results.getText(); However, after
results++, occasionally the text was corrupted. We had several
confirmations of this error on 64bit machines including 2 using Ubuntu
JJ 64 bit, and 1 using F10 64 bit. I believe I also saw the problem on
Ubuntu HH 32 bit, however no one else was able to replicate the
problem on 32 bit, so my experience may have been something else.

To work around this, we are using code like this:

const char *BackEnd::get_next_listkey(void)
{
	static char retval[128];
	const char *test = NULL;
	
	while(!results.Error()) {
		(void) g_strlcpy(retval, results.getText(), 126);
		test = results.getText();
		results++;
		GS_message((test));
		return retval;
	}
	return NULL;	
}

GS_message((test)) just prints the value of test, which is how we
determined that results++ was changing it somehow. I was able to
reproduce this consistently searching for "God" in EMTV, although
every module I tried had intermittent failures.

Matthew