The Thanh Han
there are a few places where pdftex takes the current time into account to generate certain tags. Implementing a primitive to leave out date-related things is not difficult. Can you please give some further explain what it would be useful for?
1. Regression tests for package writers. I already have set a simple setup in one or two LaTeX packages of mine, and it was very helpful when I decided to make big changes to the implementation without changing the interface. I always wanted to generalize this, but never came to it. 2. Regression testing for TeX distributions or, e.g., rpm or deb packages of texlive or teTeX for some Linux distribution. When internals change (like rearranging TEXMF trees, putting fonts in other packages, changing dependencies, etc.), the documents should not change. This is actually the reason why we are now talking about this: There are a couple of Debian developers who invest a lot of effort in automated package tests, and one of them asked whether such thing was possible in teTeX. We started discussing, now I'm here. 3. Regression testing in pdfTeX: A change that only aims at e.g. performance enhancements should not alter the document. Many other changes of course will change it.
Also note that even when such a primitive is available, the chance you get the same output for a given input file is rather low. You need to ensure that *all* relevant files (like font-related stuff, macro, figure etc.) are also the same.
That means that such tests would have to be done in a "controlled environment". That's easy for application 2, and probably not too hard for 1. For 3, it's not trivial - I don't think you can run the tests after compiling, like other programs, e.g. perl, do, and hope they will succeed on any system. But if you recreate the known-good data on *your* system just before applying a problematic patch, and test afterwards, that should work. Regards, Frank -- Frank Küster Single Molecule Spectroscopy, Protein Folding @ Inst. f. Biochemie, Univ. Zürich Debian Developer (teTeX)