[OE-core] Default rpaths in BUILD_LDFLAGS

[Martin Kelly]

On 03/08/2017 01:46 PM, Khem Raj wrote:
> On 17-03-07 16:43:47, Martin Kelly wrote:
>> Hi,
>>
>> While debugging an issue with a package that uses llvm-config to compile
>> with clang, I started hitting [rpaths] QA warnings because some output
>> executables contained absolute rpaths pointing into my build directory.
>> After tracing through the issue, I determined the rpaths to eventually be
>> originating from the setting of BUILD_LDFLAGS in meta/conf/bitbake.conf. The
>> rpath part of this was added in commit 35759f97 to the poky repo.
>
> thats for native packages alone.
>

You're right, it is for native packages only. That means this issue is 
really specific to clang or other toolchains with similar issues rather 
than being a general issue, which is good.

In this case, because llvm-config is built natively (as it needs to be 
run on the build host), and because llvm-config populates its --ldflags 
argument with the contents of BUILD_LDFLAGS, then the target build ends 
up inheriting all these flags.

>>
>> In case you're curious about the background of the issue, my project is
>> using the output of llvm-config --ldflags to set its linker flags.
>> llvm-config is populating the output --ldflags with whatever it is given for
>> CXX_LINK_FLAGS. CXX_LINK_FLAGS is being populated by the generic cmake logic
>> in cmake.bbclass, which is getting its flags from BUILD_LDFLAGS in
>> meta/conf/bitbake.conf.
>
> I think we shoud not need rpaths for target recipes. We should see if we
> can just remove it atleast for /lib /usr/lib
>

I agree we should not need them. Of course I can run a sed line to 
remove the rpaths from LLVM_LDFLAGS from 
tools/llvm-config/BuildVariables.inc (and this works just fine). 
However, I think there's a deeper issue here: All the build-time flags 
that llvm-config spits out (--cppflags, --cflags, --cxxflags) probably 
need to be replaced with target versions of those variables.

Do you agree with replacing all of those, or do you think we should 
replace only the rpaths?