sun.boot.class.path

[Jonathan Gibbons]

Jigsaw runtime folk,

Currently, javac relies on the Java runtime setting the system property 
sun.boot.class.path being set to the bootclasspath for the underlying 
JVM being used to run javac. This system property is used to locate 
platform classes when the javac -Xbootclasspath option has not been given.

Going forward, can I rely on this property always being set, in both 
legacy mode and module mode for a JVM?

The issue for javac is to how to handle compilations for older values of 
-source.

The options are:
1. rely on sun.boot.class.path being available if the javac 
-Xbootclasspath option is not set.

2. Give an error for older values of -source if -Xbootclasspath is not 
set.  Setting -Xbootclasspath is good practice anyway, and Joe Darcy has 
already advocated making this a warning.

3. Adapt the javac internals so that if javac -Xbootclasspath is not 
set, javac will use the Jigsaw default platform module, assuming Jigsaw 
is available and installed. (Eventually, this will normally always be 
the case.)

-- Jon