Use `ant -diagnostics` instead of `realpath` to get ANT_HOME

[terryzuoty]

In the makefile of stf, this parts of code is trying to define the ANT_HOME

      ANT_BINDIR:=$(dir $(firstword $(shell $(WHICH) ant$(BAT) 2>$(NULL))))
      $(warning $(WHICH) ant$(BAT) 2>$(NULL) returned)
      $(warning $(ANT_BINDIR))
      ifneq (,$(ANT_BINDIR))
        ANT_BINDIR:=$(realpath $(ANT_BINDIR)$(D)ant$(BAT))
        ANT_HOME:=$(abspath $(ANT_BINDIR)$(D)..$(D)..)
        $(warning ANT_BINDIR set to $(ANT_BINDIR))
        $(warning ANT_HOME set to $(ANT_HOME))
        $(warning Found $(ANT_BINDIR), will start build with $(ANT_LAUNCHER).  Run make configure to install the required ant version 1.10.1 or follow the prereq install instructions in build$(D)build.md)

However, this part of code doesn't work as expected on RHEL7

RHEL7:

> makefile:174: ANT_HOME not set, looking in /tmp/svttemp/git/stf/../../systemtest_prereqs/apache-ant-1.10.1
> makefile:178: Cannot find /tmp/svttemp/git/stf/../../systemtest_prereqs/apache-ant-1.10.1/lib/ant-launcher.jar, looking for ant on the PATH
> makefile:194: which ant 2>/dev/null returned
> makefile:195: /usr/bin/
> makefile:199: ANT_BINDIR set to /usr/bin/ant
> makefile:200: ANT_HOME set to /usr
> makefile:201: Found /usr/bin/ant, will start build with /usr/lib/ant-launcher.jar.  Run make configure to install the required ant version 1.10.1 or follow the prereq install instructions in build/build.md


$ make -version
GNU Make 3.82
Built for x86_64-redhat-linux-gnu
Copyright (C) 2010  Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Ubuntu16:

> makefile:174: ANT_HOME not set, looking in /tmp/svttemp/git/stf/../../systemtest_prereqs/apache-ant-1.10.1
> makefile:178: Cannot find /tmp/svttemp/git/stf/../../systemtest_prereqs/apache-ant-1.10.1/lib/ant-launcher.jar, looking for ant on the PATH
> makefile:194: which ant 2>/dev/null returned
> makefile:195: /usr/bin/
> makefile:199: ANT_BINDIR set to /usr/share/ant/bin/ant
> makefile:200: ANT_HOME set to /usr/share/ant
> makefile:201: Found /usr/share/ant/bin/ant, will start build with /usr/share/ant/lib/ant-launcher.jar.  Run make configure to install the required ant version 1.10.1 or follow the prereq install instructions in build/build.md

GNU Make 4.1
Built for x86_64-pc-linux-gnu
Copyright (C) 1988-2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Instead of using realpath in the makefile, is using ant -diagnostics a proper approach to get the correct ant.home? For example

root@113fe7939c9b:~/systemtest_prereqs# ant -diagnostics | grep "ant.home" -m 1 --max-count=1 | cut -d ':' -f 2 
 /usr/share/ant
root@113fe7939c9b:~/systemtest_prereqs# 

There should be a same way on Windows to parse the ant -diagnostics result to get the real ant.home

[terryzuoty]

HI @sxa555 , do you have any insight about this?

[sxa]

A fair comment and that sounds like a reasonable approach - that code predates me being involved with the project so I'll tag in @lumpfish :-)

[lumpfish]

@TianyuZuo - what is it you are saying is not working? Are you saying that on RHEL /tmp/svttemp/git/stf/../../systemtest_prereqs/apache-ant-1.10.1/lib/ant-launcher.jar does actually exist? Since the code is trying to find ant I can't see how running ant is going to help. What if ant is not on the path?

[terryzuoty]

Not exactly.
What I was trying to talk about is the Ant in the system which was initially used to run the top level build.xml, not the stf-downloaded Ant.

If the Ant in the system was not successfully setup, the code snippet in the makefile may fail to find the realpath of system installed Ant. Taking that RHEL machine as an example, the Ant was installed in /usr/share/ant/bin/ant but the makefile can only find its symlink /usr/bin/ant. If the ant -diagnostics was used, the ant.home would be printed out and that was correctly pointing to /usr/share/ant.

If Ant was not on the path, I don't think which ant would give back a correct path either. So this suggestion is assuming that system can find a usable Ant on Path at least, the same as the previous makefile.

[lumpfish]

Looking at the gmake doc: https://www.gnu.org/software/make/manual/html_node/File-Name-Functions.html realpath is supported to follow symlinks. Do you still have access to the machine where this is not working? I see you have included make -version output - are you saying there is an issue with realpath in make 3.82?