RFR: JDK-8218431 Improved platform checking in makefiles

[Magnus Ihse Bursie]

On 2019-02-05 15:49, Magnus Ihse Bursie wrote:
> To check for various aspects of the build or target platform, we do a 
> lot of checks like:
>    ifeq ($(OPENJDK_BUILD_OS_ENV), windows.cygwin)
>        ...
>
> The naming of those platform information variables is a bit 
> unfortunate. Yes, we know we're building OpenJDK, so why the OPENJDK_ 
> prefix? I've been wanting for a long time to do something about this 
> odd prefix, and it became more urgent after the recent fix of 
> JDK-8160926, which pushes the matter about unifying the naming of 
> build/target variables.
>
> The solution in this patch is not to rename the variables per se, but 
> to introduce an abstraction layer in terms of function calls for 
> checking platform aspects.
>
> This *really* shines when it comes to testing for multiple platforms. 
> Previously, we were required to resort to constructs such as:
>
>    ifneq ($(filter $(OPENJDK_TARGET_OS), windows solaris), )
>
> but this can now be expressed as:
>
>    ifeq ($(call isTargetOs, windows solaris), true)
>
> Or this (actually technically broken) horrible example:
>
>    ifneq (, $(findstring $(OPENJDK_TARGET_OS), linux macosx))
>
> which I had to read three times before being sure that this was the 
> correct way to replace it:
>
>    ifeq ($(call isTargetOs, linux macosx), true)
>
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8218431
> WebRev: 
> http://cr.openjdk.java.net/~ihse/JDK-8218431-improved-platform-checking/webrev.01
... and here's an updated version that fixes a typo:

http://cr.openjdk.java.net/~ihse/JDK-8218431-improved-platform-checking/webrev.02

/Magnus

>
> /Magnus
>