Month: December 2020

CMake C++ Custom Library on Windows “Undefined Reference” – No Error on Linux

Robert LohrLeave a comment

Here is the short version with a quick setup of the situation and the fix. After that, I’ll elaborate a bit.

TL;DR

Setup

I have a custom C++ library and a separate project for tests (all based on Qt 6). The test project requires the library for execution.

Here is a short excerpt of the CMake scripts, first the library, then the tests.

project(wt2-shared VERSION 2.0.0 DESCRIPTION "WorkTracker2 Shared 
Library")

# To export symbols.
add_compile_definitions(WT2_LIBRARY)

# Snip header + source definitions

add_library(${PROJECT_NAME} ${SOURCES} ${HEADERS})

target_include_directories(${PROJECT_NAME} PUBLIC include/)
target_link_libraries(wt2-shared Qt6::Core Qt6::Sql)

project(wt2-shared-test VERSION 2.0.0 DESCRIPTION "WorkTracker2 
Shared Library Tests")

# Snip header + source definitions

add_executable(${PROJECT_NAME} ${SOURCES} ${HEADERS})

target_include_directories(${PROJECT_NAME} PRIVATE ${INCLUDES})
target_link_libraries(${PROJECT_NAME} Qt6::Core Qt6::Test wt2-shared)

Error

This error only occurred on Windows, and it does not matter which toolchain I used, be it MinGW or MSVC. The result was always the same.

The following shows the MinGW error.

[100%] Linking CXX executable wt2-shared-test.exe    
CMakeFiles\wt2-shared-test.dir/objects.a(testdatasource.cpp.obj):testdatasource.cpp:(.text+0x3e5): 
    undefined reference to `__imp__ZN4Data3Sql13SqlDataSourceC1E7QString'
CMakeFiles\wt2-shared-test.dir/objects.a(testdatasource.cpp.obj):testdatasource.cpp:(.text+0x401): 
    undefined reference to `__imp__ZN4Data3Sql13SqlDataSource4loadEv'
CMakeFiles\wt2-shared-test.dir/objects.a(testdatasource.cpp.obj):testdatasource.cpp:(.text+0x514): 
    undefined reference to `__imp__ZN4Data3Sql13SqlDataSourceC1E7QString'	
CMakeFiles\wt2-shared-test.dir/objects.a(testdatasource.cpp.obj):testdatasource.cpp:(.text+0x530): 
    undefined reference to `__imp__ZN4Data3Sql13SqlDataSource4loadEv'
collect2.exe: error: ld returned 1 exit status
mingw32-make[2]: *** 
[wt2-shared-test\CMakeFiles\wt2-shared-test.dir\build.make:142: 
wt2-shared-test/wt2-shared-test.exe] Error 1

Solution

The add_library definition in the CMakeLists.txt was incomplete.
To make it work, I added SHARED because I want a shared library.

add_library(${PROJECT_NAME} SHARED ${SOURCES} ${HEADERS})

Continue reading, though, to get the full picture. There is more to it than just making the library a shared one.

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CMake CLI Parameter “generator-name” Usage

Robert LohrLeave a comment

This topic shouldn’t even require a blog post, but I find the CMake CLI usage rather odd when it comes to specifying a generator. Here’s a shortened "-h" output.

> cmake -h
Usage

cmake [options] <path-to-source>
cmake [options] <path-to-existing-build>
cmake [options] -S <path-to-source> -B <path-to-build>

Specify a source directory to (re-)generate a build system for it in the
current working directory.  Specify an existing build directory to
re-generate its build system.

Options
-S <path-to-source>          = Explicitly specify a source directory.
-B <path-to-build>           = Explicitly specify a build directory.
-C <initial-cache>           = Pre-load a script to populate the cache.
-D <var>[:<type>]=<value>    = Create or update a cmake cache entry.
-U <globbing_expr>           = Remove matching entries from CMake cache.
-G <generator-name>          = Specify a build system generator.
-T <toolset-name>            = Specify toolset name if supported by
                                generator.
-A <platform-name>           = Specify platform name if supported by
                                generator.

    ...snip...

Generators

The following generators are available on this platform (* marks default):
Visual Studio 16 2019        = Generates Visual Studio 2019 project files.
                                Use -A option to specify architecture.
Visual Studio 15 2017 [arch] = Generates Visual Studio 2017 project files.
                                Optional [arch] can be "Win64" or "ARM".

    ...snip...

Borland Makefiles            = Generates Borland makefiles.
* NMake Makefiles              = Generates NMake makefiles.
NMake Makefiles JOM          = Generates JOM makefiles.
MSYS Makefiles               = Generates MSYS makefiles.
MinGW Makefiles              = Generates a make file for use with
                                mingw32-make.
Unix Makefiles               = Generates standard UNIX makefiles.

    ...snip...
    
Kate - Ninja                 = Generates Kate project files.
Kate - Unix Makefiles        = Generates Kate project files.
Eclipse CDT4 - NMake Makefiles
                            = Generates Eclipse CDT 4.0 project files.
Eclipse CDT4 - MinGW Makefiles
                            = Generates Eclipse CDT 4.0 project files.
Eclipse CDT4 - Ninja         = Generates Eclipse CDT 4.0 project files.
Eclipse CDT4 - Unix Makefiles= Generates Eclipse CDT 4.0 project files.

These generator options do not look like valid parameter values to the "-G" option. But they are. So, if you want to compile on Windows using MinGW, you have to use this.

> cmake -S ../src -B ./ -G "MinGW Makefiles"

Or, if you prefer Visual Studio project files:

> cmake -S ../ -B ./ -G "Visual Studio 15 2017 Win64"

This "syntax" looks weird, and it tripped me for about 10 minutes until I found a sample and understood how it works.

Road to the Perfect Mini ITX PC (Part 5): Other Small Form-Factor ITX Cases

Robert LohrLeave a comment

Previously on “Road to the Perfect Mini ITX PC”:

  1. Fractal Design Core 500
  2. NZXT H200
  3. Fractal Design Meshify C
  4. Lian Li TU150

The first two cases I had bought were before I became aware of all the mass-market and niche options that existed at that time. Not only have I learned about the DAN Case, NCase M1, and Streacom DA2, but companies have released more cases during the past year. I’m talking about the NZXT H1, the Cooler Master NR200, or, recently, Phanteks’ second attempt at the Evolv Shift. Even Lian Li’s TU150 landed during that time, my current case. There are even so many more cases, like the Louqe Ghost S1, the FormD T1, Sliger SM560, and many more.

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