CMake Compile with external FMT option

[BobManMasher]

Hi,
Compiling latest SPDLOG on an Armel Debian Buster system for use with Gerbera 1.9.0. Gerbera compile warns me I need to use SPDLOG with SPDLOG_FMT_EXTERNAL set to avoid conflicts. I have compiled the latest FMT (8.0.1) and when I use the variable in my cmake, I get the following message:

'sudo cmake .. -DWITH_SPDLOG_FMT_EXTERNAL=1
-- Build spdlog: 1.9.2
-- Build type: Release
-- Generating example(s)
-- Generating install
-- Configuring done
-- Generating done
CMake Warning:
Manually-specified variables were not used by the project:
WITH_SPDLOG_FMT_EXTERNAL'

Has the variable been set and will the compile use the external fmt?

[tt4g]

WITH_SPDLOG_FMT_EXTERNAL is not working.
You need to set CMake variable SPDLOG_FMT_EXTERNAL to ON for using external fmt library.

[BobManMasher]

Thanks for your help,. I have tried all these ways of setting external FMT:
'-DWITH_SPDLOG_FMT_EXTERNAL=1'
'-DWITH_SPDLOG_FMT_EXTERNAL=ON'
'-DWITH_SPDLOG_FMT_EXTERNAL=YES'

and get the same message i.e.
'CMake Warning:
Manually-specified variables were not used by the project:
WITH_SPDLOG_FMT_EXTERNAL'

When I then compile Gerbera, it also tells me that SPDLOG has been made with its own FMT rather than external.

[tt4g]

Replace -DWITH_SPDLOG_FMT_EXTERNAL=ON to -DSPDLOG_FMT_EXTERNAL=ON (remove WITH_ prefix).

[BobManMasher]

Hi
I run CMAKE as follows:
'cmake -DSPDLOG_FMT_EXTERNAL=ON'

and this is the content of the spdlogConfig.cmake file:

cat /usr/local/lib/cmake/spdlog/spdlogConfig.cmake
Copyright(c) 2019 spdlog authors
Distributed under the MIT License (http://opensource.org/licenses/MIT)

####### Expanded from @PACKAGE_INIT@ by configure_package_config_file() #######
####### Any changes to this file will be overwritten by the next CMake run ####
####### The input file was spdlogConfig.cmake.in ########

get_filename_component(PACKAGE_PREFIX_DIR "${CMAKE_CURRENT_LIST_DIR}/../../../" ABSOLUTE)

macro(set_and_check _var _file)
set(${_var} "${_file}")
if(NOT EXISTS "${_file}")
message(FATAL_ERROR "File or directory ${_file} referenced by variable ${_var} does not exist !")
endif()
endmacro()

macro(check_required_components _NAME)
foreach(comp ${${_NAME}_FIND_COMPONENTS})
if(NOT ${NAME}${comp}_FOUND)
if(${_NAME}FIND_REQUIRED${comp})
set(${_NAME}_FOUND FALSE)
endif()
endif()
endforeach()
endmacro()

####################################################################################

find_package(Threads REQUIRED)

set(SPDLOG_FMT_EXTERNAL OFF)
set(config_targets_file spdlogConfigTargets.cmake)

if(SPDLOG_FMT_EXTERNAL)
include(CMakeFindDependencyMacro)
find_dependency(fmt CONFIG)
endif()

include("${CMAKE_CURRENT_LIST_DIR}/${config_targets_file}")

check_required_components(spdlog)

When I compile Gerbera which uses spdlog, I see a message saying that I haven't built spdlog with external fmt. I am using fmt-8.0.1 BTW which I compilled first and installed. There seems to be no other fmt packages installed when I do a package check. Would you please clarify how?

[BobManMasher]

I have a build directory i.e. spdlog-1.9.2/build which I cleared before I started the build last night. The downloaded files are in the directory above so actually my command line is cmake .. -DSPDLOG_FMT_EXTERNAL=ON

[tt4g]

Can you find CMakeCache.txt in CMake build directory? It records CMake cache variables.
In my case, SPDLOG_FMT_EXTERNAL:BOOL=ON is recorded as follows.

$ mkdir build 
$ cd build
$ cmake .. -DSPDLOG_FMT_EXTERNAL=ON
$ grep -r SPDLOG_FMT_EXTERNAL .
$ grep SPDLOG_FMT_EXTERNAL CMakeCache.txt
SPDLOG_FMT_EXTERNAL:BOOL=ON
SPDLOG_FMT_EXTERNAL_HO:BOOL=OFF

[BobManMasher]

I have exactly the same on my system:

root@Nas:/build/spdlog-1.9.2/build# grep SPDLOG_FMT_EXTERNAL CMakeCache.txt
SPDLOG_FMT_EXTERNAL:BOOL=ON
SPDLOG_FMT_EXTERNAL_HO:BOOL=OFF

[tt4g]

If SPDLOG_FMT_EXTERNAL=ON is set only on the command line, then CMakeCache.txt and SPDLOG_FMT_EXTERNAL in spdlogConfig.cmake will have the same value.
Please check the variables of the two files in the build directory and they should have the same value.

My guess is that /usr/local/lib/cmake/spdlog/spdlogConfig.cmake is the file generated when you installed spdlog before.
Try to install it again.

[BobManMasher]

I don't know what is creating /usr/local/lib/cmake/spdlog/spdlogConfig.cmake but trying all sorts of options and edits to CMakeFiles etc. failed to make an impact. In the end, I purged the spdlog install, deleted the spdlogConfig.cmake file and rebuilt spdlog and was bemused to find spdlogconfig was not recreated. The build message seems to have gone when I cmake gerbera and the build has now completed and Gerbera 1.9.0 is now running on my test server.
Thanks for your patience and help - Bob