RFR: JDK-8171859: Configure check for modular boot jdk needs to be updated

[Mandy Chung]

Using —-patch-module is one option.

Alternatively, you can use other new options such as:
  $ java --dry-run -m jdk.compiler/com.sun.tools.javac.Main

This stops before invoking the main method.

or 
  $ java —-list-modules 

This lists the observable modules in the image.

Mandy

> On Dec 22, 2016, at 1:39 AM, Erik Joelsson <erik.joelsson at oracle.com> wrote:
> 
> Hello,
> 
> Configure has a check to see if the boot jdk is module aware/enabled. Like many others, the build needs to adapt its behavior when using such a boot jdk. The current check is no longer compatible with the latest JDK 9 builds:
> 
> java -version --patch-module foo=bar
> WARNING: Unknown module: foo specified in --patch-module
> 
> I propose a simple adjustment, to instead specify java.base as the module to patch. I also made it explicit that the directory to patch from does not exist.
> 
> I'm open to suggestions on better tests though, but would prefer if they can be as simple as checking for a command line argument.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8171859
> 
> Patch:
> 
> diff -r 84c58139cbd3 common/autoconf/boot-jdk.m4
> --- a/common/autoconf/boot-jdk.m4
> +++ b/common/autoconf/boot-jdk.m4
> @@ -305,7 +305,9 @@
>   BOOT_JDK_SOURCETARGET="-source 8 -target 8"
>   AC_SUBST(BOOT_JDK_SOURCETARGET)
> 
> -  ADD_JVM_ARG_IF_OK([--patch-module foo=bar], dummy, [$JAVA])
> +  # Use a non existing directory as the directory will be scanned otherwise
> +  # and can potentially take a lot of time.
> +  ADD_JVM_ARG_IF_OK([--patch-module java.base=SOME_DIR_THAT_DOES_NOT_EXIST], dummy, [$JAVA])
>   AC_MSG_CHECKING([if Boot JDK supports modules])
>   if test "x$JVM_ARG_OK" = "xtrue"; then
>     AC_MSG_RESULT([yes])
> 
> 
> /Erik
>