[llvm-dev] Distinguishing trunk version number from release

[Dimitry Andric via llvm-dev]

On 3 Jan 2018, at 18:24, James Y Knight via llvm-dev <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 :

.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


> 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?


> 2. Change the minor version of the first release.
> 
> Leave trunk as X.0 as now, but on the release branch, increment the version to X.1.
> 
> 7.0.0--------8.0.0-----------------9.0.0------...
>            \-7.1.0----7.1.1      \-8.1.0----8.1.1
> 
> I'd marginally favor #2, because that's similar to how GCC is doing it now, but what do others think?

As far as I can see, the first variant would not really work for the FreeBSD ports system as-is, since it has silently assumed the second-level version number to be smaller than 10.  But maybe I'm reading the ports infrastructure makefiles incorrectly.

That said, as long as there is a way to identify the (end-user visible) clang or llvm version where certain features or bugs were introduced, both variants would be OK.

-Dimitry

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