RFR (S): Supports statically linking TSAN runtime into the launcher with Clang

[Man Cao]

FYI, I used the pre-built LLVM 8.0.0 for Ubuntu 18.04 from here:
http://releases.llvm.org/download.html#8.0.0

I will also update the wiki page if everyone likes this workaround.

-Man


*From: *Man Cao <manc at google.com>
*Date: *Mon, May 13, 2019 at 10:08 PM
*To: * <tsan-dev at openjdk.java.net>

Hi all,
>
> Can I have reviews for this patch that hopefully will unblock us from the
> libtsan.so's version issue?
> https://cr.openjdk.java.net/~manc/tsan20190513/webrev.00/
>
> This is a workaround for the version issue with libtsan.so in GCC. If we
> build the JDK with Clang, we will have a newer version of the TSAN runtime
> statically linked into the launcher:
> $ nm images/jdk/bin/java | grep tsan_symbolize
> 000000000048e640 W __tsan_symbolize_external
> 000000000048e650 W __tsan_symbolize_external_ex
>
> In the long term, Java TSAN will still work with GCC, but stack trace
> symbolization will be broken until OpenJDK can be built with GCC9, which
> contains the new version of libtsan.so that we need.
> Also need to write distinct values to the global variable in
> libAbstractNativeLoop.cpp, otherwise some optimization in Clang could treat
> the variable as constant, and TSAN reports "Write of size 1" instead of
> "size 4".
>
> I have tested this with both LLVM 8.0.0 and GCC.
>
> -Man
>