[OE-core] [meta-clang] oe-core and meta-clang llvm coexsting?

[Martin Kelly]

On 03/30/2017 04:58 PM, Martin Kelly wrote:
> On 03/30/2017 12:31 PM, Khem Raj wrote:
>>
>>
>> On 3/30/17 12:20 PM, Martin Kelly wrote:
>>> Hi,
>>>
>>> I'm trying to integrate the meta-clang version of LLVM 4.0 (used for
>>> recipes that need a newer LLVM version) alongside the oe-core version of
>>> LLVM 3.3 (used for mesa). I'd like some recipes to use LLVM 4.0 and some
>>> to use LLVM 3.3 and for them not to collide with each other.
>>>
>>> Right now, once the meta-clang layer is enabled, the recipes collide
>>> because they both provide llvm-common.bb. I tried explicitly versioning
>>> llvm-common, which makes them no longer collide. However, mesa then
>>> fails to build because the meta-clang version of LLVM installs
>>> llvm-config into the native common sysroot in
>>
>> merging all llvm-common into a single recipe might be good
>

I thought more about this issue. Absent some clever solution that allows 
us to unify the wrappers (which is difficult due to the issues I 
mentioned in the last mail), I think we have three routes that could 
work to at least allow meta-clang and meta-oe to exist in the same Yocto 
workspace without breakage:

(a) Instead of installing llvm-config into 
${SYSROOT_DESTDIR}${bindir_crossscripts} -- which causes collisions when 
meta-clang and meta-oe both try to overwrite the same shared file -- 
install into ${D}{bindir}llvm-config, and install the binary llvm-config 
into ${D}${bindir}/llvm-config${PV}. Recipes requiring LLVM will then 
need to depend on either llvm-common3.3 or llvm-common4.0, but at least 
there will be no collision or ambiguity which one gets used.

(b) Use a common wrapper in 
${SYSROOT_DESTDIR}${bindir_crossscripts}/llvm-config that does what the 
meta-oe current version does; just exec 
${SYSROOT_DESTDIR}${bindir_crossscripts}/llvm-config${WANT_LLVM_RELEASE}. 
Let the meta-oe LLVM 3.3 install the binary llvm-config into 
${SYSROOT_DESTDIR}${bindir_crossscripts}/llvm-config3.3 and let the 
meta-clang LLVM 4.0 install its wrapper llvm-config into 
${SYSROOT_DESTDIR}${bindir_crossscripts}/llvm-config4.0. meta-clang will 
have to use the second wrapper script because it needs to edit 
TARGET_CFLAGS and similar to avoid compiling target binaries using 
native flags (due to the CMake LLVM build which appears not to respect 
cross-compile).

(c) Use a common llvm-config wrapper in 
${SYSROOT_DESTDIR}${bindir_crossscripts}/llvm-config that does a 
hardcoded check for WANT_LLVM_RELEASE. If the version is 4.0 or greater, 
then edit the TARGET_CFLAGS and similar, otherwise don't.

It seems to me that all these options are undesireable, but (a) is 
probably least so.

Khem and others: which option would you like me to pursue, or do you 
have an alternate suggestion?

Thanks,
Martin