Improve mergestaticlibs

[jschueller]

Use linux part only on linux platforms
Should fix #180

[filip-stenstrom]

Can you explain this a bit more, and how it solves the Mingw issue in #192?

1. Reading the doc it's not clear to me how it's valid that target_sources(...) can accept object files. To me it looks like it expects .c and .h files, and that one should use target_link_libraries(...) with the object files?
2. How can we use $<TARGET_OBJECTS:...> if libtarget is not specified as add_library(... OBJECT)? At least I don't see that we specify it as OBJECT.

[jschueller]

it seems #192 build failed because it did not have the ls command to list object files

I tried several things including creating an intermediate OBJECT library but it did not work but curiously target_sources worked, so seems I have to dig on the cmake side

[filip-stenstrom]

Internal test of the MinGW installation shows that there are some issues, likely expat (and possibly other libs are not merged or found):

Output...

set -eu; \
	cd Test/test_installation; \
	rm -rf build && mkdir -p build; \
	cd build; \
	cmake -DFMIL_HOME=/c/<...>/install_mingw_w64 -G "MSYS Makefiles" ..; \
	cmake --build .; \
	ctest 

...

[ 50%] Linking C executable main.exe
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0xa7): undefined reference to `XML_ParserFree'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x115): undefined reference to `XML_StopParser'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x2d3): undefined reference to `XML_ParserFree'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x2e2): undefined reference to `XML_ParserCreate_MM'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x2fd): undefined reference to `XML_SetUserData'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x313): undefined reference to `XML_SetElementHandler'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x322): undefined reference to `XML_SetCharacterDataHandler'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x396): undefined reference to `XML_Parse'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x426): undefined reference to `XML_GetErrorCode'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x42d): undefined reference to `XML_ErrorString'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x438): undefined reference to `XML_GetCurrentLineNumber'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x476): undefined reference to `XML_ParserFree'
C:/<...>/install_mingw_w64/lib/libfmilib.a(fmi_xml_context.c.obj):fmi_xml_context.c:(.text+0x22b): undefined reference to `XML_StopParser'
C:/<...>/install_mingw_w64/lib/libfmilib.a(unzip.c.obj):unzip.c:(.text+0x1ce5): undefined reference to `inflateEnd'
C:/<...>/install_mingw_w64/lib/libfmilib.a(unzip.c.obj):unzip.c:(.text+0x2b55): undefined reference to `inflateEnd'
C:/<...>/install_mingw_w64/lib/libfmilib.a(unzip.c.obj):unzip.c:(.text+0x2bee): undefined reference to `inflateInit2_'
C:/<...>/install_mingw_w64/lib/libfmilib.a(unzip.c.obj):unzip.c:(.text+0x2e98): undefined reference to `inflate'
C:/<...>/install_mingw_w64/lib/libfmilib.a(unzip.c.obj):unzip.c:(.text+0x2eed): undefined reference to `crc32'
C:/<...>/install_mingw_w64/lib/libfmilib.a(unzip.c.obj):unzip.c:(.text+0x2fb1): undefined reference to `crc32'
C:/<...>/install_mingw_w64/lib/libfmilib.a(unzip.c.obj):unzip.c:(.text+0x3205): undefined reference to `inflateEnd'
collect2.exe: error: ld returned 1 exit status

[jschueller]

are you using an external, dynamic expat lib ?

[filip-stenstrom]

Building with bundled expat:

mkdir -p build_mingw_w64
cd build_mingw_w64 && \
		cmake -DCMAKE_INSTALL_PREFIX=../install_mingw_w64 \
			-DFMILIB_GENERATE_DOXYGEN_DOC=0 \
			-DFMILIB_BUILD_WITH_STATIC_RTLIB=0 \
			-DFMILIB_BUILD_TESTS=1 \
			-DFMILIB_TEST_LOCALE=1  \
			-DCMAKE_BUILD_TYPE=Release \
			-DCMAKE_C_FLAGS="-m64" -DCMAKE_CXX_FLAGS="-m64" -DCMAKE_SHARED_LINKER_FLAGS="-m64" -DCMAKE_EXE_LINKER_FLAGS="-m64" \
			-G "MSYS Makefiles" \
			../.