Building with cmake's fetch content using a cross compiler

[pfeatherstone]

So I have the following in my CMakeLists.txt file:

include(FetchContent)

set(FMT_TEST FF CACHE INTERNAL "disabling fmt tests")

FetchContent_Declare(
        fmt
        GIT_REPOSITORY  https://github.com/fmtlib/fmt.git
        GIT_TAG         8.0.1
        GIT_PROGRESS    TRUE
        USES_TERMINAL_DOWNLOAD TRUE
)

FetchContent_MakeAvailable(fmt)

...
target_link_libraries(mybinary
        PRIVATE fmt::fmt
)

When cross-compiling with say an arm compiler, i get undefined reference errors like this:

<artificial>:(.text.startup+0x1588): undefined reference to `fmt::v8::vprint(fmt::v8::basic_string_view<char>, ...

I'm cross-compiling like this:

cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER=arm-openwrt-linux-gcc -DCMAKE_CXX_COMPILER=arm-openwrt-linux-g++ ..

So i'm not specifying a toolchain file.

Now, is this a cmake bug in the FetchContent module, or is this a libfmt bug?

Cheers

[pfeatherstone]

This works fine when not cross compiling. Note that a short term solution is to use fmt::fmt-header-only

[pfeatherstone]

Turns out the issue is because i'm compiling with -flto. Looking closely at the logs, i can see the following:

arm-openwrt-linux-ar: CMakeFiles/fmt.dir/src/format.cc.o: plugin needed to handle lto object

I thinks that's it.