Re: libupb.a needed by anything using protobuf .cmake files

On Sat, 2025-05-24 at 12:12 +0800, Xi Ruoyao wrote:
> On Fri, 2025-05-23 at 23:20 +0200, Pierre Labastie wrote:
> > /usr/lib/cmake/protobuf/protobuf-targets.cmake contains:
> > -----
> > add_library(protobuf::libupb STATIC IMPORTED)
> > -----
> > So if we remove libupb.a as done in protobuf instructions (since
> > protobuf-31), any CMakeLists.txt using this file will fail with:
> > ----------
> > CMake Error at /usr/lib/cmake/protobuf/protobuf-targets.cmake:132
> > (message):
> >   The imported target "protobuf::libupb" references the file
> > 
> >      "/usr/lib/libupb.a"
> > 
> >   but this file does not exist.  Possible reasons include:
> > 
> >   * The file was deleted, renamed, or moved to another location.
> > 
> >   * An install or uninstall procedure did not complete successfully.
> > 
> >   * The installation package was faulty and contained
> > 
> >      "/usr/lib/cmake/protobuf/protobuf-targets.cmake"
> > 
> >   but not all the files it references.
> > -----------
> > So I think we should remove the line "rm /usr/lib/libupb.a" when
> > installing protobuf. libupb.a is about 520KB in size...
> 
> The problem here is not to save space.  It's just it shouldn't be
> installed even per upstream documentation
> (https://github.com/protocolbuffers/protobuf/blob/main/upb/README.md):
> 
>    While upb offers a C API, the C API & ABI are not stable. For this
>    reason, upb is not generally offered as a C library for direct
>    consumption, and there are no releases.
> 
> I'll try to figure out a way to prevent it from being installed.

Tentative patch:

diff --color -Naur protobuf-31.0/cmake/install.cmake protobuf-31.0.patched/cmake/install.cmake
--- protobuf-31.0/cmake/install.cmake	2025-05-14 23:37:13.000000000 +0800
+++ protobuf-31.0.patched/cmake/install.cmake	2025-05-24 12:39:08.572837445 +0800
@@ -37,9 +37,6 @@
 if (protobuf_BUILD_LIBPROTOC)
     list(APPEND _protobuf_libraries libprotoc)
 endif (protobuf_BUILD_LIBPROTOC)
-if (protobuf_BUILD_LIBUPB)
-  list(APPEND _protobuf_libraries libupb)
-endif ()
 
 foreach(_library ${_protobuf_libraries})
   if (UNIX AND NOT APPLE)
diff --color -Naur protobuf-31.0/cmake/libprotoc.cmake protobuf-31.0.patched/cmake/libprotoc.cmake
--- protobuf-31.0/cmake/libprotoc.cmake	2025-05-14 23:37:13.000000000 +0800
+++ protobuf-31.0.patched/cmake/libprotoc.cmake	2025-05-24 12:28:03.095300298 +0800
@@ -16,8 +16,8 @@
   set_target_properties(libprotoc PROPERTIES
     LINK_DEPENDS ${protobuf_SOURCE_DIR}/src/libprotoc.map)
 endif()
-target_link_libraries(libprotoc PRIVATE libprotobuf)
-target_link_libraries(libprotoc PUBLIC libupb ${protobuf_ABSL_USED_TARGETS})
+target_link_libraries(libprotoc PRIVATE libprotobuf libupb)
+target_link_libraries(libprotoc PUBLIC ${protobuf_ABSL_USED_TARGETS})
 protobuf_configure_target(libprotoc)
 if(protobuf_BUILD_SHARED_LIBS)
   target_compile_definitions(libprotoc


-- 
Xi Ruoyao <[email protected]>
School of Aerospace Science and Technology, Xidian University

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