[OE-core] [RFC][PATCH] cmake: respect ${S} and ${B}

[Koen Kooi]

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Ross Burton schreef op 05-12-13 01:38:
> Hi,
> 
> This is a Request For Comments because it changes behaviour of the cmake
> class and I'm not entirely knowledgeable in cmake.
> 
> For some reason, cmake.bbclass doesn't use ${S} and ${B}, but instead has
> it's own variables OECMAKE_SOURCEPATH ("." by default) and
> OECMAKE_BUILDPATH ("" by default).  Those defaults meant that the build
> happened in the source directory, which conveniently was ${S}.  Unless
> ${B} was also set, in which case it all broke.
> 
> I don't see a good reason for cmake.bbclass having it's own special
> versions of ${S} and ${B}, so this patch drops them and replicates some
> of the logic in autotools.bbclass: specifically the part where if ${S}
> and ${B} are different, delete ${B} before building.  This ensures that
> switching machine doesn't re-use the same build directory, which was the
> cause of me going back to look at this (libproxy trying to use the nuc
> sysroot when I'm building for qemux86-64).
> 
> Some open questions:
> 
> 1) As I understand it cmake has more reliable support for out-of-tree
> builds than autotools.

Next to toolchain files it's the only positive think I can say about cmake.

> If this is the case should cmake.bbclass set B ?= "${WORKDIR}/build"

In opencv I set it to ${WORKDIR}/build-${TARGET_ARCH} to match the autotools
class, but that was a while ago. All the other meta-oe recipes seem to use
what you propose.

> , or leave setting of B to separatebuilddir.inc?  Are there known recipes
> using cmake that fail with out-of-tree builds?
> 
> 2) Is dropping OECMAKE_SOURCEPATH and OECMAKE_BUILDPATH acceptable?
> Nothing in oe-core uses them and there's three (IIRC) recipes in meta-oe
> that use them. Assuming the answer to (1) is "separatebuilddir.inc" then
> the only fallout should be these recipes using in-tree builds until
> OECMAKE_BUILDPATH is replaced with B.

I'm not sure, but I think I favour the cmake.bbclass path, it's only a
handfull of recipe that need straightforward changes.

regards,

Koen
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