Can't use protobuf in cmakelists.txt

Question

I am trying to run the example given in protobuf repo here, the c++ version. I have successfully installed the library and am able to run the Makefile. But on running the CMakeLists.txt, I get this error:

CMake Error at CMakeLists.txt:9 (find_package):
  Could not find a package configuration file provided by "protobuf" with any
  of the following names:

    protobufConfig.cmake
    protobuf-config.cmake

  Add the installation prefix of "protobuf" to CMAKE_PREFIX_PATH or set
  "protobuf_DIR" to a directory containing one of the above files.  If
  "protobuf" provides a separate development package or SDK, be sure it has
  been installed.


-- Configuring incomplete, errors occurred!
See also "/home/cortana/Projects/CppProjects/proto/build/CMakeFiles/CMakeOutput.log".
See also "/home/cortana/Projects/CppProjects/proto/build/CMakeFiles/CMakeError.log".

I have updated my LD_LIBRARY_PATH but this error is still there. How do I remove this error?

EDIT:
CMakeLists.txt:

# Minimum CMake required
cmake_minimum_required(VERSION 2.8.12)

# Project
project(protobuf-examples)

include(FindProtobuf)
# Find required protobuf package
find_package(protobuf CONFIG REQUIRED)

if(protobuf_VERBOSE)
  message(STATUS "Using Protocol Buffers ${Protobuf_VERSION}")
endif()

set(CMAKE_INCLUDE_CURRENT_DIR TRUE)

set(CMAKE_PREFIX_PATH
    ${CMAKE_PREFIX_PATH}
    ${THIRDPARTY_DIR}/protobuf-3.1.0
)

include_directories(${ProtobufIncludePath})

# http://www.cmake.org/Wiki/CMake_FAQ#How_can_I_build_my_MSVC_application_with_a_static_runtime.3F
if(MSVC AND protobuf_MSVC_STATIC_RUNTIME)
  foreach(flag_var
      CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
      CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
    if(${flag_var} MATCHES "/MD")
      string(REGEX REPLACE "/MD" "/MT" ${flag_var} "${${flag_var}}")
    endif(${flag_var} MATCHES "/MD")
  endforeach()
endif()

foreach(example add_person list_people)
  set(${example}_SRCS ${example}.cc)
  set(${example}_PROTOS addressbook.proto)

  #Code Generation
  if(protobuf_MODULE_COMPATIBLE) #Legacy Support
    protobuf_generate_cpp(${example}_PROTO_SRCS ${example}_PROTO_HDRS ${${example}_PROTOS})
    list(APPEND ${example}_SRCS ${${example}_PROTO_SRCS} ${${example}_PROTO_HDRS})
  else()

    foreach(proto_file ${${example}_PROTOS})
      get_filename_component(proto_file_abs ${proto_file} ABSOLUTE)
      get_filename_component(basename ${proto_file} NAME_WE)
      set(generated_files ${basename}.pb.cc ${basename}.pb.h)
      list(APPEND ${example}_SRCS ${generated_files})

      add_custom_command(
        OUTPUT ${generated_files}
        COMMAND protobuf::protoc
        ARGS --cpp_out ${CMAKE_CURRENT_BINARY_DIR} -I ${CMAKE_CURRENT_SOURCE_DIR} ${proto_file_abs}
        COMMENT "Generating ${generated_files} from ${proto_file}"
        VERBATIM
      )
    endforeach()
  endif()

  #Executable setup
  set(executable_name ${example}_cpp)
  add_executable(${executable_name} ${${example}_SRCS} ${${example}_PROTOS})
  if(protobuf_MODULE_COMPATIBLE) #Legacy mode
    target_include_directories(${executable_name} PUBLIC ${PROTOBUF_INCLUDE_DIRS})
    target_link_libraries(${executable_name} ${PROTOBUF_LIBRARIES})
  else()
    target_link_libraries(${executable_name} protobuf::libprotobuf)
  endif()

endforeach()

EDIT 2:
After trying for 2 hours, I couldn't fix the CMakeLists.txt provided by google examples. I wrote this basic one and it works for me:

PROJECT(protopuff)
CMAKE_MINIMUM_REQUIRED (VERSION 3.5)
SET(CMAKE_CXX_FLAGS "-g -Wall -Werror -std=c++11")

INCLUDE(FindProtobuf)
FIND_PACKAGE(Protobuf REQUIRED)
INCLUDE_DIRECTORIES(${PROTOBUF_INCLUDE_DIR})
PROTOBUF_GENERATE_CPP(PROTO_SRC PROTO_HEADER addressbook.proto)
ADD_LIBRARY(proto ${PROTO_HEADER} ${PROTO_SRC})


INCLUDE_DIRECTORIES(${CMAKE_CURRENT_BINARY_DIR})
ADD_EXECUTABLE(${CMAKE_PROJECT_NAME}_add add_person.cc)
ADD_EXECUTABLE(${CMAKE_PROJECT_NAME}_list list_people.cc)
TARGET_LINK_LIBRARIES(${CMAKE_PROJECT_NAME}_add proto ${PROTOBUF_LIBRARY})
TARGET_LINK_LIBRARIES(${CMAKE_PROJECT_NAME}_list proto ${PROTOBUF_LIBRARY})

Solution

Your problem is here:

find_package(protobuf CONFIG REQUIRED)

The name should start with uppercase: Protobuf. And that is the reason why your version is working; because in there, you have used correct case (last code snippet line 6):

find_package(Protobuf REQUIRED)

Here cmake documentation for find_package

The command searches for a file called <name>Config.cmake or <lower-case-name>-config.cmake for each name specified.

Comments

[Jake Sylvestre]

Why is the config not required?

[ifyalciner]

I have just copied the line from where it is working in the question.(last code section 6th line). It is his decision not to use.

[Jake Sylvestre]

Got it. Yeah, it's interesting all the example documentation has Config Required, but no actual config files