Openj9: Global ENV var or configure option to enable debugging in OpenJ9

[babsingh]

Currently, multiple environment variables need to be set to enable debugging in OpenJ9.

Reference: https://blog.openj9.org/2018/06/05/debugging-openj9-in-docker-with-gdb/

export UMA_DO_NOT_OPTIMIZE_CCODE="1"
export VMDEBUG="-g3 -fno-inline -O0"
export VMLINK="-g -O0"
export enable_debug=yes
export enable_optimized=no
export enable_optimize=no
export CXXFLAGS="-O0 -g3"
export CFLAGS="-O0 -g3"
export BUILD_CONFIG=debug

It's tedious to keep track of all the environment variables. So, a global environment variable or configure option can be added to set all the required environment variables ... to enable debugging for OpenJ9.

[babsingh]

fyi - @DanHeidinga @mstoodle @pshipton @keithc-ca

[babsingh]

@dnakamura do CMAKE changes have a single trigger point to enable debugging in OpenJ9?

[pshipton]

OpenJ9 should hook into the OpenJDK configure options to control debugging.

[babsingh]

OpenJ9 should hook into the OpenJDK configure options to control debugging.

Build instructions for OpenJDK: http://hg.openjdk.java.net/jdk8/jdk8/raw-file/tip/README-builds.html

OpenJDK build instructions already support high level configure options to enable debugging. Example: --enable-debug, --with-debug-level=level (level=release|fastdebug|slowdebug) etc. We must detect these options and then, appropriately set debugging environment variables for OpenJ9.

[keithc-ca]

We should understand the _intent_ of those OpenJDK configure options to be sure we connect to the right one(s).

[babsingh]

from the OpenJDK build documentation,

--enable-debug sets the debug level to fastdebug (this is a shorthand for --with-debug-level=fastdebug).

debug (non-optimized, -g plus assert logic); fastdebug (optimized, -g plus assert logic)

documentation didn't explicitly define slowdebug. i think debug == slowdebug.

from bash ./configure --with-freemarker-jar=/root/freemarker.jar --help, I found the following debug related options:

  --enable-debug          set the debug level to fastdebug (shorthand for
                          --with-debug-level=fastdebug) [disabled]
  --disable-debug-symbols disable generation of debug symbols [enabled]
  --disable-zip-debug-info
                          disable zipping of debug-info files [enabled]
  --with-debug-level      set the debug level (release, fastdebug, slowdebug)
                          [release]
  --debug-configure       Run the configure script with additional debug
                          logging enabled.

for any other information about the intent of OpenJDK configure options, we may have to dive into the code.

[pdbain-ibm]

Please note that setting those variables per https://github.com/eclipse/openj9/issues/2078#issue-329567921 causes the build to break. See https://github.com/eclipse/openj9/issues/2088.

[pdbain-ibm]

2088 affects Java 9 but not Java 8.