[Question]: How to maintain order of libraries

[hoehermann]

Current Behavior

Using

target_link_libraries(main PRIVATE rust_staticlib m)

results in

/usr/bin/cc -g "main.c.o" -o main  -lm librust_staticlib.a 

leading to

/build/rustc-Oic09u/rustc-1.65.0+dfsg0ubuntu1/library/std/src/f64.rs:88: undefined reference to `round'

.

Expected Behavior

Using

target_link_libraries(main PRIVATE rust_staticlib m)

results in

/usr/bin/cc -g "main.c.o" -o main librust_staticlib.a -lm

leading to successful build.

Steps To Reproduce

https://github.com/hoehermann/purple-presage in I am trying to link a rust staticlib into a shared object. The staticlib seems to need some math functions, so I added m to the target_link_libraries stanza:

add_executable(main "src/c/main.c")
target_link_libraries(main PRIVATE rust_staticlib m)

Am I using corrosion wrong? Or is this a common CMake issue I have not encountered so far?

This may or may not be related to #335.

I added the verbose outputs as requested. I hope it helps in spite of the libpurple stuff adding a lot of clutter.

Environment

- OS: Ubuntu 22.04
- CMake: 3.24.0
- CMake Generator: Unix Makefiles

CMake configure log with Debug log-level

-- PURPLE_INCLUDE_DIRS: /usr/include/libpurple;/usr/include/glib-2.0;/usr/lib/x86_64-linux-gnu/glib-2.0/include
-- PURPLE_LIBRARY_DIRS: /usr/lib;/usr/lib/x86_64-linux-gnu
-- PURPLE_LIBRARIES: purple;glib-2.0
-- Rust Target: x86_64-unknown-linux-gnu
-- Parsed Target triple: arch: x86_64, vendor: unknown, OS: linux, env: gnu
-- Parsed Target triple: arch: x86_64, vendor: unknown, OS: linux, env: gnu
-- Using Corrosion as a subdirectory
-- Found 1 targets in package purple-presage-backend
-- TARGET purple_presage_backend produces byproducts libpurple_presage_backend.a;;
-- Corrosion created the following CMake targets: purple_presage_backend
-- PURPLE_PLUGIN_DIR: /usr/lib/purple-2
-- Output directory property (target purple_presage_backend): ARCHIVE_OUTPUT_DIRECTORY dir: output_directory-NOTFOUND
-- Setting IMPORTED_LOCATION for target purple_presage_backend-static to `REDACTED/build/libpurple_presage_backend.a`.
-- Adding command to copy byproducts `libpurple_presage_backend.a` to REDACTED/build/libpurple_presage_backend.a
-- Configuring done
-- Generating done
-- Build files have been written to: REDACTED/build

CMake Build step log

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�[0m�[0m�[1m�[32m    Finished�[0m dev [unoptimized + debuginfo] target(s) in 0.23s
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/usr/bin/ld: libpurple_presage_backend.a(sled-6db45d69e2a9ad3e.sled.09113f11-cgu.5.rcgu.o): in function `std::f64::<impl f64>::round':
/build/rustc-Oic09u/rustc-1.65.0+dfsg0ubuntu1/library/std/src/f64.rs:88: undefined reference to `round'
/usr/bin/ld: libpurple_presage_backend.a(rand-7f1ebc9c3a94bcda.rand.29cfc123-cgu.14.rcgu.o): in function `std::f64::<impl f64>::ln::{{closure}}':
/build/rustc-Oic09u/rustc-1.65.0+dfsg0ubuntu1/library/std/src/f64.rs:427: undefined reference to `log'
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/build/rustc-Oic09u/rustc-1.65.0+dfsg0ubuntu1/library/std/src/f64.rs:384: undefined reference to `exp'
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[jschwe]

Which version of corrosion are you using?

Edit: to expand a bit. The actual issue here in my opinion is that corrosion doesn't link in libm automatically for you. Unless you turned off the option, e.g. by passing NO_STD to corrosion_import_crate, I would like to know which version of corrosion this occured on.

In response to the question you asked:

As far as I know CMake doesn't guarantee a particular order for the libraries for a specific target and is free to reorder. The issue you are facing is because you are declaring libm to be a dependency of main, when it actually is a dependency of your rust static lib. As such you should do target_link_libraries(your_rust_lib INTERFACE c_lib).
Cmake is aware of the dependency in this case and will order them accordingly.

But again, for libm corrosion should do this automatically.

[hoehermann]

I did not specify and version. FetchContent defaulted to corrosion 0.4.1 at 4a134df.

target_link_libraries(your_rust_lib INTERFACE c_lib) solves the issue. So I was using cmake wrong. Thank you very much.