cmake: add optional static and shared build options

[sreimers]

refs #771

[alfredh]

many thanks, this looks like a good and flexible approach.

it also does not require any user changes, which is good for Juha's project.

[alfredh]

I think we can merge this now ...

[juha-h]

I pulled latest re:

/usr/src/libbaresip-android$ grep SHARED re/CMakeLists.txt 
option(LIBRE_BUILD_SHARED "Build shared library" ON)
if(LIBRE_BUILD_SHARED)
  add_library(re-shared SHARED $<TARGET_OBJECTS:re-objs>)
if(LIBRE_BUILD_SHARED)

and made libre Android build:

/usr/src/libbaresip-android$ make libre.a
cd re && \
rm -rf build && rm -rf .cache && mkdir build && cd build && \
cmake .. \
	-DANDROID=ON -DANDROID_PLATFORM=23 -DCMAKE_SYSTEM_NAME=Android -DCMAKE_SYSTEM_VERSION=23 -DCMAKE_TOOLCHAIN_FILE=/opt/Android/ndk/25.2.9519653/build/cmake/android.toolchain.cmake -DANDROID_ABI=arm64-v8a -DCMAKE_ANDROID_ARCH_ABI=arm64-v8a -DCMAKE_SKIP_INSTALL_RPATH=ON -DCMAKE_C_COMPILER=aarch64-linux-android23-clang -DCMAKE_CXX_COMPILER=aarch64-linux-android23-clang++ -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DCMAKE_BUILD_TYPE=Release \
	-DCMAKE_FIND_ROOT_PATH="/opt/Android/ndk/25.2.9519653;/usr/src/libbaresip-android/openssl" \
	-DOPENSSL_VERSION_MAJOR=3 \
	-DOPENSSL_ROOT_DIR=/usr/src/libbaresip-android/openssl && \
cmake --build . --target re -j
-- The C compiler identification is Clang 14.0.7
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /opt/Android/ndk/25.2.9519653/toolchains/llvm/prebuilt/linux-x86_64/bin/clang - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Performing Test COMPILER_SUPPORTS_WATOMIC
-- Performing Test COMPILER_SUPPORTS_WATOMIC - Success
-- Looking for backtrace
-- Looking for backtrace - not found
-- Could NOT find Backtrace (missing: Backtrace_LIBRARY) 
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - not found
-- Check if compiler accepts -pthread
-- Check if compiler accepts -pthread - yes
-- Found Threads: TRUE  
-- Found ZLIB: /opt/Android/ndk/25.2.9519653/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/aarch64-linux-android/23/libz.so (found version "1.2.12") 
-- Found OpenSSL: /usr/src/libbaresip-android/openssl/libcrypto.a (found suitable version "3.1.0", minimum required is "1.1.1")  
-- Looking for arc4random
-- Looking for arc4random - found
-- Looking for syslog.h
-- Looking for syslog.h - found
-- Looking for getopt.h
-- Looking for getopt.h - found
-- Looking for unistd.h
-- Looking for unistd.h - found
-- Looking for res_ninit
-- Looking for res_ninit - not found
-- Looking for thrd_create
-- Looking for thrd_create - not found
-- Looking for accept4
-- Looking for accept4 - found
-- Looking for epoll_create
-- Looking for epoll_create - found
-- Looking for kqueue
-- Looking for kqueue - not found
-- Looking for sys/prctl.h
-- Looking for sys/prctl.h - found
-- Could NOT find Backtrace (missing: Backtrace_LIBRARY) 
-- Configuring done
-- Generating done
-- Build files have been written to: /usr/src/libbaresip-android/re/build
...
gmake[4]: Entering directory '/usr/src/libbaresip-android/re/build'
[  1%] Building C object CMakeFiles/re-objs.dir/src/async/async.c.o
...

[100%] Building C object CMakeFiles/re-objs.dir/rem/vidmix/vidmix.c.o
gmake[4]: Leaving directory '/usr/src/libbaresip-android/re/build'
[100%] Built target re-objs
gmake[4]: Entering directory '/usr/src/libbaresip-android/re/build'
[100%] Linking C static library libre.a
gmake[4]: Leaving directory '/usr/src/libbaresip-android/re/build'
[100%] Built target re
gmake[3]: Leaving directory '/usr/src/libbaresip-android/re/build'

And the result was that (like before) only static lib was build. I don't need shared libs, but I am just wondering.

[sreimers]

You just specify only the static target with --target re, thats fine.

[alfredh]

hi Juha,

in your cmake command line options you can now select which type of libs your want to build:

option(LIBRE_BUILD_SHARED "Build shared library" ON)
option(LIBRE_BUILD_STATIC "Build static library" ON)

$ cmake -DLIBRE_BUILD_SHARED=OFF .
$ make

i.e. you can skip the target if you want.