Hey Adam,
You can try to set `POSITION_INDEPENDENT_CODE` in the Abseil build. That
should at least get around the error you're seeing here. However, the
reason we don't explicitly support this is because in many situations it's
an ODR violation. If two shared libraries both use Abseil via static
linkage, there will be two definitions of absl. Assuming they're both
identical, this isn't a problem in most of the absl code. However, when it
comes to things like the hash seed you can end up breaking every hash table
in very difficult to debug ways. I think the only way this could work is
if none of the other shared libraries (and the code that's using them) were
using Abseil, and you don't need protoc (which also uses Abseil).
That seems like a pretty brittle requirement to place on anyone, and I
think a feature request for Abseil to ship a single shared library might be
a better approach. They already do this for windows, but not on linux or
mac.
-Mike
On Friday, June 16, 2023 at 2:59:43 AM UTC-7 Adam Dembek wrote:
> We want to use shared libprotobuf.so for many tools to not increase size
> of each binary.
> We know we can build protobuf with -Dprotobuf_BUILD_SHARED_LIBS=ON
> -Dprotobuf_INSTALL_SUPPORTED_FROM_MODULE=ON -Dprotobuf_ABSL_PROVIDER=module
> but then both protobuf and absl are build as shared library.
> We need to deliver over 80 libraries. It would easier if we could only
> deliver single libprotobuf.so file like in the past when protobuf was not
> using absl.
>
> Is it possible to use static absl libraies and link it libprotobuf.so ?
> I tried firts build abls independentlay with
>
> cmake -S ${ABSL_SOURCE} -B ${ABSL_PROD_DIR}
> -DCMAKE_PREFIX_PATH=${ABSL_PROD_DIR}
> -DCMAKE_INSTALL_PREFIX=${ABSL_PROD_DIR} -DABSL_ENABLE_INSTALL=ON
> -DABSL_USE_EXTERNAL_GOOGLETEST=OFF -DABSL_FIND_GOOGLETEST=OFF
>
> This created static absl libraries.
>
> And then build protobuf with
> -DCMAKE_PREFIX_PATH=${ABSL_PROD_DIR}/lib64/cmake/absl
> -Dprotobuf_ABSL_PROVIDER=package-DCMAKE_CXX_STANDARD=14
> -Dprotobuf_BUILD_SHARED_LIBS=ON
>
> But it fails with
>
> [ 36%] Linking CXX shared library libprotobuf.so
> /usr/bin/ld:
> /user/adembek/PROD/absl/build/absl_2023_01_25/lib64/libabsl_cord.a(cord.cc.o):
>
> relocation R_X86_64_32 against `.rodata' can not be used when making a
> shared object; recompile with -fPIC
> /usr/bin/ld:
> /user/adembek/PROD/absl/build/absl_2023_01_25/lib64/libabsl_cord.a(cord_analysis.cc.o):
>
> relocation R_X86_64_32 against `.rodata' can not be used when making a
> shared object; recompile with -fPIC
> /usr/bin/ld:
> /user/adembek/PROD/absl/build/absl_2023_01_25/lib64/libabsl_die_if_null.a(die_if_null.cc.o):
>
> relocation R_X86_64_32 against `.rodata' can not be used when making a
> shared object; recompile with -fPIC
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