[Mesa-dev] [PATCH] Android: Fix LLVM duplicated symbols linking for N and M

[Emil Velikov]

On 21 August 2017 at 17:17, Rob Herring <robh at kernel.org> wrote:
> On Fri, Aug 18, 2017 at 7:27 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>> On 18 August 2017 at 20:46, Rob Herring <robh at kernel.org> wrote:
>>> Both statically linking libLLVMCore and dynamically linking libLLVM causes
>>> duplicated symbols in gallium_dri.so and it fails to dlopen. We don't
>>> really need to link libLLVMCore, but just need generated headers to be
>>> built first. Dynamically linking to libLLVM instead is enough to do
>>> that. Thanks to Qiang Yu for finding the root cause.
>>>
>> Nice find indeed, thanks.
>>
>> This reminds me - a small task for a rainy day.
>> - Wire the version script files into the Android build - see the
>> autoconf snippet below.
>> It will hide the hundreds of symbols when static linking LLVM (aka
>> sidestep the current issue) and make the binary noticeably smaller.
>>
>> gallium_dri_la_LDFLAGS += \
>>        -Wl,--version-script=$(top_srcdir)/src/gallium/targets/dri/dri.sym
>
> About 60K smaller out of 12MB. Is that inline with what you'd expect?
>
Sounds a bit smaller than expected, but every little helps ;-)

> before:
>    text    data     bss     dec     hex filename
> 12164054         420384  352476 12936914         c566d2
> out/target/product/linaro_x86_64/system/lib64/dri/gallium_dri.so
>
> after:
>    text    data     bss     dec     hex filename
> 12104616         419816  352476 12876908         c47c6c
> out/target/product/linaro_x86_64/system/lib64/dri/gallium_dri.so
>
>
> The change is trivial, though I'm not sure if there's any downside to
> setting --undefined-version (The Android build system turns this off).
>
There's no actual symbol versioning, just restriction of the actual
exported symbols.
Thus things should work w/o -Wl,--undefined-version so I wouldn't touch it.

-Emil