RFR: JDK-8198724 Refactor FLAGS handling in configure

[Erik Joelsson]

Hello Magnus,

Nice to finally see this posted! Overall very nice improvement.

On 2018-02-26 15:40, Magnus Ihse Bursie wrote:
> The current way we're handling FLAGS (CFLAGS/CXXFLAGS, LDFLAGS, etc) 
> is laden with technical debt. It's a sorry mess, hard to do anything 
> constructive about.
>
> This is the first step towards a better solution. The main goal is to 
> have a set of more specific flags, more like how the SYSROOT flags 
> work today, that can be individually included, instead of a huge 
> CFLAGS_JDKLIB.
>
> To make such a change manageable, this first step will (almost) only 
> refactor the autoconf code, but will output the same flags in the 
> spec.gmk.
>
> To minimize special cases, I have accepted the following differences:
> * On linux/gcc, we will get a -m<bits>, e.g. -m64 always (as on 
> aix/solaris).
> * On macosx/clang, we will get a -m<bits>, e.g. -m64 always (as on 
> aix/solaris).
> * On macosx/clang, we will now "hardcode" the max/min version number 
> without dots.
I would advocate a simple bash replace to remove the dots, like this:
MACOSX_VERSION_MIN_NODOTS=${MACOSX_VERSION_MIN//\./}
> * On macosx/clang, the JVM_CFLAGS for the build toolchain will now 
> also get an -fPIC (this was mysteriously missing before).
> * On windows/microsoft, the build toolchain will now get -nologo added 
> as well, and also -homeparams for debug builds.
> * On solaris/solstudio, the JDKEXE flags will now include -errfmt, and 
> CFLAGS_JDKEXE will include -errtags=yes. The duplication of 
> -errtags=yes in CXXFLAGS_JDKLIB is removed.
> * On solaris/solstudio, we now always use -KPIC as pic flag. 
> (Previously, we used -xcode=pic32 on sparc, but this is equivalent to 
> -KPIC, so there's no reason for a special case.)
> * On solaris/solstudio, we now use e.g. "-Wc,-Qrm-s" instead of 
> "-Qoption cg -Qrm-s" for C++ as well as for C code. The two formats 
> are equivalent (for passing options to a certain compilation phase), 
> and there was no reason to use different ones for C and C++.
>
> And for clarity, I have also renamed some exported flags to clearly 
> show that they are consumed by LIBJSIG and ADLC. I have also renamed 
> "/STACK" on the Microsoft linker to "-stack", to match how we write 
> options elsewhere.
>
> I believe none of these should have any real effect, but if anything, 
> they could probably be considered bug fixes.
>
> I have considered whitespace and ordering differences as irrelevant.
>
In some cases ordering may be relevant, hopefully the COMPARE_BUILD run 
will uncover if that's the case. If those are ok, then I'm basically 
happy with this transformation.
> I have manually verified that the generated spec.gmk and 
> buildjdk-spec.gmk matches this (no changes apart from the one listed 
> above) for linux/x64/gcc, solaris/sparcv9/solstudio, 
> windows/x64/microsoft and macosx/x64/clang, for release and fastdebug.
>
> I am also currently running a test job using the COMPARE_BUILD 
> functionality on our internal build system.
>
> I would appreciate if comments are more in the form of "think of this 
> for subsequent updates to the flag handling" rather than requests to 
> change this patch, at least for requests that are just not small 
> fixes. (I've been juggling this for a while, trying to get it right...)
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8198724
> WebRev: 
> http://cr.openjdk.java.net/~ihse/JDK-8198724-refactor-flags-step-1/webrev.01
>
Comments on things I saw, not necessarily needing fixes now:

In flags.m4, MACHINE_FLAG and COMPILER_TARGET_BITS_FLAG are redundant 
without comment.

flags-cflags.m4, FLAGS_SETUP_SHARED_LIBS, comments out of 
date/irrelevant like:
# Default works for linux, might work on other platforms as well.

Solaris -errtags is not needed in CFLAGS_WARNINGS_ARE_ERRORS.

Given that TOOLCHAIN_MINIMUM_VERSION_gcc="4.7", perhaps we can remove 
the check for -Wno-X on gcc 4.4.

/Erik

> /Magnus
>