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Re: gcc: -ftest-coverage and -auxbase
On Wed, Jun 12, 2019 at 10:17 PM <David.Taylor@dell.com> wrote:
> When doing a build, we use a pipe between GCC and GAS.
> And because we wish to do some analysis of the assembly code,
> we do not use -pipe but instead do '-S -c -'. And this has worked
> fine for many years.
Can you please show us complete command-lines here? -S -c -
will only assemble (and require source from standard input
and produce output in -.s).
> I was recently looking into collecting some coverage information.
> To that end, I added --coverage to the invocation line. And it slowed
> things down by more than an order of magnitude!
> Investigating, it appears that the problem is the writing of the GCNO
> We do our builds on a build cluster with a lot of parallelism.
> With the result that a dozen machines are each doing a bunch
> of writes to the file '-.gcno' in an NFS mounted directory.
> Rather than have a full, not incremental, build take 5-10 minutes,
> It takes 4 hours. And rather than have each of several thousand
> compiles produce their own GCNO file, they all get overwritten...
> Grep'ing around, I found '-auxbase'. If I correctly understand it,
> when compiling
> I could simply say
> -auxbase $(@:%.o=%)
> The problem is that in common.opt, auxbase is marked RejectDriver.
> It looks like removing it would some my problem. Anyone have a reason
> why removing that would be a bad idea? Or have a different solution?