cmake: dependencies between CMake targets work only if the dependent target is imported

[mmomtchev]

subprojects/cmMod:

cmake_minimum_required(VERSION 3.5)

project(cmMod)
set (CMAKE_CXX_STANDARD 14)

include_directories(${CMAKE_CURRENT_BINARY_DIR})

add_library(cmModLib1 STATIC cmMod1.cpp)
add_library(cmModLib2 STATIC cmMod2.cpp)
# This is what is not working
target_link_libraries(cmModLib1 PUBLIC cmModLib2)

meson.build:

project('cmakeSubTest', ['c', 'cpp'])

cm = import('cmake')

sub_pro = cm.subproject('cmMod')
# require only the first one
sub_dep = sub_pro.dependency('cmModLib1', include_type: 'system')

exe1 = executable('main', ['main.cpp'], dependencies: [sub_dep])
test('test1', exe1)

Result:

INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /usr/bin/ninja -v
[1/4] /usr/local/bin/g++ -Isubprojects/cmMod/libcmModLib1.a.p -Isubprojects/cmMod -I../subprojects/cmMod -Isubprojects/cmMod/__CMake_build -I../subprojects/cmMod/__CMake_build -fdiagnostics-color=always -D_GLIBCXX_ASSERTIONS=1 -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -std=gnu++14 -O0 -g -g -DcmModClass=cmModClass1 -MD -MQ subprojects/cmMod/libcmModLib1.a.p/cmMod.cpp.o -MF subprojects/cmMod/libcmModLib1.a.p/cmMod.cpp.o.d -o subprojects/cmMod/libcmModLib1.a.p/cmMod.cpp.o -c ../subprojects/cmMod/cmMod.cpp
[2/4] /usr/local/bin/g++ -Imain.p -I. -I.. -fdiagnostics-color=always -D_GLIBCXX_ASSERTIONS=1 -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -O0 -g -isystem../subprojects/cmMod -isystemsubprojects/cmMod -isystem../subprojects/cmMod/__CMake_build -isystemsubprojects/cmMod/__CMake_build -MD -MQ main.p/main.cpp.o -MF main.p/main.cpp.o.d -o main.p/main.cpp.o -c ../main.cpp
[3/4] rm -f subprojects/cmMod/libcmModLib1.a && gcc-ar csrDT subprojects/cmMod/libcmModLib1.a subprojects/cmMod/libcmModLib1.a.p/cmMod.cpp.o
[4/4] /usr/local/bin/g++  -o main main.p/main.cpp.o -Wl,--as-needed -Wl,--no-undefined subprojects/cmMod/libcmModLib1.a
FAILED: main 
/usr/local/bin/g++  -o main main.p/main.cpp.o -Wl,--as-needed -Wl,--no-undefined subprojects/cmMod/libcmModLib1.a
/usr/bin/ld: main.p/main.cpp.o: in function `main':
/home/mmom/src/meson/test cases/cmake/29 cascading deps/build/../main.cpp:14: undefined reference to `cmModClass2::cmModClass2(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >)'
/usr/bin/ld: /home/mmom/src/meson/test cases/cmake/29 cascading deps/build/../main.cpp:16: undefined reference to `cmModClass2::getStr[abi:cxx11]() const'
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.

The problem is that when resolving the dependencies, only targets that have IMPORTED_LOCATION or IMPORTED_IMPLIB result in an actual library dependency in meson:

https://github.com/mmomtchev/meson/blob/648a3ddd65a6010dbfaf42bf9de624c2ae47bccd/mesonbuild/cmake/tracetargets.py#L118

Only imported targets have these, internal CMake targets have to be included via LINK_LIBRARIES / INTERFACE_LINK_LIBRARIES - in the code, these are used only for recursion.

[mmomtchev]

Waiting on #13071 to submit a PR because both modify the same code

[mmomtchev]

This is something that seems to have been implemented:

meson/mesonbuild/cmake/interpreter.py

Line 1073 in 46b3c1c

# First handle inter target dependencies

But this code is never triggered, maybe it used to work at some point, then ti was broken