analyzer Precise `strdup`

Currently strdup (and strndup) return an unknown pointer, which can make things very imprecise. Instead we should:

[ ] Return a pointer to freshly allocated memory, the same way as malloc.
[ ] Create a corresponding blob as its value.
[ ] Blob size should come from the argument string constant or blob size.
[ ] Blob contents should copy the argument blob contents or summarize the string constant.
[ ] strndup should additionally only have maximum length n and copy as long prefix.

Aug 21 '23 14:08 sim642

@nathanschmidt will tackle this as it is quite related to his string domain work.

Aug 22 '23 12:08 michael-schwarz

Now that the thesis is done, will this still be worked on or not? I don't recall where I originally noticed this, but this may be quite crucial now because silver searcher has lots of likely-spurious race warnings related to a strndup. I don't know for sure whether this would avoid them, but we might have to do this ourselves since the PLDI paper is high priority.

Sep 14 '23 08:09 sim642

Now that the thesis is done, will this still be worked on or not?

Sorry I haven't found the time to do so yet. I'll try to do this next week, let me know if that is soon enough

Sep 16 '23 12:09 nathanschmidt

If you can get around to it next week, I think that is timely enough; However, please don't feel obligated to do it if you don't want to, as the thesis is officially over now.

Sep 16 '23 13:09 michael-schwarz

After some more digging into silver searcher it appears that strdup might not be the main biggest hurdle. Rather it seems proper value analysis of thread-local variables (#876) is more crucial to get rid of unknown pointers that cause imprecise type-based memory accesses.

Sep 18 '23 07:09 sim642

Nathan has finished his thesis now and will sadly not have time to work on this, so I unassigned him.

Sep 23 '23 14:09 michael-schwarz