On 2015-09-08, Scott Kostyshak wrote:
> On Mon, Sep 7, 2015 at 9:57 PM, Enrico Forestieri <for...@lyx.org> wrote:
>> On Mon, Sep 07, 2015 at 04:11:07PM -0400, Scott Kostyshak wrote:
>>> On Sun, May 03, 2015 at 02:02:06AM +0200, Enrico Forestieri wrote:
>>> > On Sat, May 02, 2015 at 07:03:53PM -0400, Scott Kostyshak wrote:
>>> My question is, when the user begins a preview, shouldn't the .aux
>>> always removed so there is a fresh compile?
No.
>>> I think the answer has to do with somehow there is a faster
>>> compilation if that .aux can be reused.
Yes.
>>> What determines whether the aux should be used or regenerated though?
>>> LyX or LaTeX?
Aux files are (re)generated with every LaTeX run. Whether they are outdated
or not is determined by LaTeX based on the content:
* if they are outdated (e.g. new or removed sections, targets on a
different page, ...) LaTeX will issue the usual "labels may have changed"
warning, triggering a new LaTeX run.
* if they are still up-to-date, one LaTeX run will suffice to get a document
with valid cross-links - this is checked automatically by LaTeX after any
compilation run.
There are cases where you this simple logic may fail:
a) includeonly,
>> There are cases where the previously generated aux files are useful and
>> removing them causes wrong results. For example, if you include a number
>> of child documents, say a child for each chapter, like this:
>> \begin{document}
>> \include{chap1}
>> \include{chap2}
>> ...
>> \end{document}
>> latex generates aux files for each included child. If you later are only
>> working on chapter 4, you could do
>> \includeonly{chap4}
>> \begin{document}
>> \include{chap1}
>> \include{chap2}
>> ...
>> \end{document}
>> and only chap4.tex gets compiled while cross-references to other chapters
>> are still correct because their aux files are still there.
> And how do we know that the aux files do not need updating? Does this
> depend on whether the timestamp of the corresponding .tex is newer or
> older?
There is no timestamp comparison. The \includeonly option is also just for
speedup during editing/preview. The user is responsible to include files
that have changed significantly or live with an approximation of the
document as preview. The final compilation should in any case be done with
all documents included.
b) removal of packages or other definitions from the preamble:
When latexing "per hand", I mostly just leave the *.aux files in the
folder for late use (which may be after some years...)
Sometimes get an compilation error when removing a language option
from a document and re-compiling: "language .... not defined".
This is caused by the *.aux file still containing use cases for this
language.
The problem usually goes away for the next run (because the aux-file was
updated).
LyX could trigger removal of *.aux files if the same error occures in two
successive compilation runs.
Günter
