Den 15/11/2010 kl. 00.10 skrev Dimitry Andric:
> On 2010-11-14 23:29, Erik Cederstrand wrote:
>> I noticed that two consecutive builds of (GCC-built) Clang don't produce
>> identical binaries. This is true for clang, clang++ and tblgen. I asked on
>> the llvm-dev list yesterday, and it turns out it's because GCC uses a random
>> seed on some symbols. Apparently, this can be controlled with the
>> -frandom-seed flag. I haven't tested if this is also the case for
>> Clang-built Clang.
>>
> [...]
> So this is all on purpose, and I think it would be a bad idea to disable
> it, unless we fully understand the consequences.
>
> On the other hand, the requirement "The string should be different for
> every file you compile", could possibly be fulfilled. Maybe by using
> the filename, relative to $SRCDIR, that is being compiled as "seed"?
>
> This would be unique for each compiled file, but still give the same
> result for each build, and also be independent of the particular machine
> you are building on.
I was thinking of something along the same lines. I think we agree that it only
needs to be random across files, not across builds. Someone on llvm-dev also
suggested using the path (either full or relative to src/) as a seed.
Where in the build scripts would I need to add this flag? Something like:
CXXFLAGS += -frandom-seed=${.TARGET}
in src.conf?
Thanks,
Erik
