[CMake] FindProtobuf error: _protobuf_include_path empty

[Antonio Mancina]

Hi all,

I've been fighting against this error for the last two hours.

When I try to setup a cmake-based project which builds some protobuf
related stuff, something strange happens.

My sample cmake directives follow:

================================
find_package(Protobuf REQUIRED)

include_directories(${PROTOBUF_INCLUDE_DIRS})

PROTOBUF_GENERATE_CPP(PROTO_SRCS PROTO_HDRS
    ${CMAKE_SRC_DIR}/Libraries/FileA.proto
    ${CMAKE_SRC_DIR}/Libraries/FileB.proto
)

add_library(MyLibrary SHARED
    ${PROTO_SRCS}
)

target_link_libraries(MyLibrary
    ${PROTOBUF_LIBRARIES}
)
================================

When building this code, the build system was silently failing at building
the pb.h and pb.cc files. I followed all the code path within the module
and found that the problem is related to the _protobuf_include_path not
being given any value before the PROBUF_GENERATE_CPP call, so that the row

list(APPEND _protobuf_include_path -I ${ABS_PATH})

translates to

-I ;/the/path/in/abs_path

with the semi-colon between the -I and the path. This gives rise to
problems in protoc invocation.

I solved this by introducing the following if-then-else:

list(LENGTH _protobuf_include_path _list_num)
if(${_list_num} EQUAL 0)
    set(_protobuf_include_path -I ${ABS_PATH})
else()
    list(APPEND _protobuf_include_path -I ${ABS_PATH})
endif()

but I'd like to understand what I'm doing wrong and why I'm seeing this.

Thanks all!

A.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.cmake.org/pipermail/cmake/attachments/20130205/95455df0/attachment-0001.htm>