[ccache] ccache interrupt handling bug

Joel Rosdahl joel at rosdahl.net
Mon Aug 17 19:09:11 UTC 2015

Tom Lane <tgl at sss.pgh.pa.us> wrote:
> Actually, that's a bug not just a cosmetic problem, because it introduces
> a race condition.  Consider this sequence of events:
> * make launches "ccache gcc -o test.o test.c"
> * user types control-C
> * ccache receives SIGINT and exits
> * make does unlink("test.o") to clean up after failed compile step, which
>   it thinks is done
> * gcc creates test.o
> * gcc receives SIGINT and exits
> We're left with a probably-broken test.o in the filesystem, despite
> make's attempt to clean up.  Now, the window for this is pretty narrow,
> but I think it could happen: I don't believe that sending signals to
> multiple processes is atomic in most kernels.

Yes, sounds like a race condition that could happen.

I just pushed this change as a fix:
Opinions on it are welcome.

[...] I wonder whether it's sane to do "clean_up_pending_tmp_files();" when
> gcc is still on the loose.

clean_up_pending_tmp_files only deletes temporary files used to catch the
compiler's stdout and stderr, so that shouldn't be a problem.

-- Joel

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