[llvm-dev] Distinguishing trunk version number from release

[Dimitry Andric via llvm-dev]

> On 4 Jan 2018, at 23:31, James Y Knight <jyknight at google.com> wrote:
> 
> 
> 
> On Thu, Jan 4, 2018 at 3:04 PM, Dimitry Andric <dimitry at andric.com <mailto:dimitry at andric.com>> wrote:
> On 3 Jan 2018, at 18:24, James Y Knight via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> >
> > I'd like to propose that trunk always have a version number which is in between versions used by the previous release branch, and before the versions used in the next release branch.
> >
> > Right now, trunk is sharing the 7.0.0 number, which will also be used by the next release 4 months from now. Since some people use and release snapshots of clang from trunk (e.g. the Android NDK), it'd be helpful to be able to more reliably distinguish this.
> >
> > This is both confusing in general, and means that if you're writing an #if checking the version (which of course ought to be avoided when possible, but is sometimes the best answer), it is more difficult than it needs to be to do the right thing.
> >
> > E.g., a check like this will erroneously think that trunk, now, is Clang 7, and has fixed this hypothetical bug.
> > #if __clang_major__ >= 7
> > // Do something which was buggy before Clang 7.
> > #endif
> 
> Yes, this is often done in the FreeBSD ports system, sometimes using the major version in the source, but more often in Makefiles, where the X.Y.Z version is condensed to just 'XY', as shown in https://github.com/freebsd/freebsd-ports/blob/master/lang/v8/Makefile#L36 <https://github.com/freebsd/freebsd-ports/blob/master/lang/v8/Makefile#L36> :
> 
> .if ${COMPILER_TYPE} == clang
> CXXFLAGS+=      -Wno-nested-anon-types -Wno-unused-function -Wno-unused-private-field
> MAKE_ENV+=      LINK=clang++
> .if ${COMPILER_VERSION} >= 34
> CXXFLAGS+=      -Wno-unused-const-variable
> .if ${COMPILER_VERSION} >= 35
> CXXFLAGS+=      -Wno-tautological-undefined-compare
> .if ${COMPILER_VERSION} >= 36
> CXXFLAGS+=      -Wno-unused-local-typedef
> .endif
> .endif
> .endif
> 
> 
> That seems a very unfortunate scheme, especially considering the differing definition of the same-named variable in FreeBSD core's makefiles:
> https://github.com/freebsd/freebsd/blob/d67d8724ce34e69801d9018e6bf76afed2ca3841/share/mk/bsd.README <https://github.com/freebsd/freebsd/blob/d67d8724ce34e69801d9018e6bf76afed2ca3841/share/mk/bsd.README>
> """
> COMPILER_VERSION
> 		A numeric constant equal to:
> 		     major * 10000 + minor * 100 + tiny
> 		for the compiler's self-reported version.
> """

Yes indeed, it is an unfortunate difference between the base system and the ports system.  I feel that the major * 10000 + minor * 100 + tiny constant is more useful, but the maintainers of the ports system decided to use a shorter constant.


> I don't think that's a good reason to not use X.99 for clang versions, however -- the FreeBSD makefile can easily translate that to X9 if it likes, or, change their definition.
> 
> 
> > I see a couple alternatives for improving this:
> >
> > 1. Change the way we version trunk.
> >
> > After creating release branch for X.0, change trunk to version X.99 instead of (X+1).0. Thus, trunk would always have a .99 minor release. The release branch would be incremented from X.99 to (X+1).0 upon creation.
> >
> > 6.99.0-------7.99.0----------------8.99.0------...
> >            \-7.0.0----7.0.1      \-8.0.0----8.0.1
> 
> Probably 6.9, 7.9 and such would be enough, since 7.1 and 7.2 won't ever appear in the recent "new versioning scheme", and even older versions never reached past the .9 second level version?
> 
> Perhaps so, but I greatly prefer the implication that "99" has that it's not a real version, which "9" is much less suggestive of.

Yes, that is certainly a good reason.  The second scheme would be similar in this respect, e.g. if the minor version number is 0, it is always trunk version.

-Dimitry

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