[mosquitto] Static linking broken

[silabs-beta]

Description / Steps to reproduce the issue

I try to use the libmosquitto package in my project with static linking. I use -static linker flag and I get the linker flags for the package like this: pkg-config --libs --static libmosquitto. The output of the pkg-config is -lmosquitto.

Expected behavior

The flags provided by pkg-config should work as is.

Actual behavior

The linker fails like this: cannot find -lmosquitto: No such file or directory
It happens because the static library is called libmosquitto.dll.a, see the file list here.
If I link with the -lmosquitto.dll flag, the link succeeds.
I think the libmosquitto.dll.a should be renamed to libmosquitto.a, but I don't know where to look at.
I think libmosquittopp is affected too, but I haven't tried it.

Verification

• I have verified that my MSYS2 is up-to-date before submitting the report (see https://www.msys2.org/docs/updating/)

Windows Version

MINGW64_NT-10.0-19045

MINGW environments affected

• MINGW64
• MINGW32
• UCRT64
• CLANG64
• CLANG32
• CLANGARM64

Are you willing to submit a PR?

No response

[podsvirov]

@silabs-beta, can you confirm that #20605 fix your problem? (you can rebuild package himself or download prebuild Artifacts from Checks)

[silabs-beta]

Unfortunately no, I get various linker errors like these

undefined reference to `__imp_mosquitto_lib_init'
undefined reference to `__imp_mosquitto_new'
undefined reference to `__imp_mosquitto_connect_callback_set'
undefined reference to `__imp_mosquitto_disconnect_callback_set'
undefined reference to `__imp_mosquitto_message_callback_set'
undefined reference to `__imp_mosquitto_log_callback_set'
undefined reference to `__imp_mosquitto_connect'
...

I didn't expect such a quick response, so I opened a ticket in the mosquitto repo too.
eclipse/mosquitto#3035

[Biswa96]

It is not an issue. You forgot to define LIBMOSQUITTO_STATIC macro for static linking. We could also add that macro in pkgconfig file.

[silabs-beta]

@Biswa96 Shall I replace the -lmosquitto linker flag to -lmosquitto_static? Is this what you meant?
It doesn't work, either, I get the same undefined reference errors.

[Biswa96]

I meant to define LIBMOSQUITTO_STATIC macro in compiler flag. For example, gcc -DLIBMOSQUITTO_STATIC -static test.c <put the rest things here>

[silabs-beta]

I don't understand how could a compiler flag solve a linker issue.
Anyway, I tried it, and the original issue still persists: cannot find -lmosquitto: No such file or directory

[silabs-beta]

@podsvirov , your fix renames libmosquitto_static.a to libmosquitto.a. But the libmosquitto.dll.a should be renamed to libmosquitto.a instead.

[Biswa96]

But the libmosquitto.dll.a should be renamed to libmosquitto.a instead.

No. The .dll.a are import library and those are correctly named.

[silabs-beta]

I agree, it can be correctly named in theory, but the experience shows that the fix doesn't work. If I rename the one with the .dll.a suffix, then the build succeeds.

[Biswa96]

Could you provide any sample code to reproduce the issue?

[silabs-beta]

Sure, you can use e.g. basic-1.c
and compile it like this: gcc basic-1.c -static -lmosquitto -o subscribe.exe

[Biswa96]

Try this command gcc -static -DLIBMOSQUITTO_STATIC basic-1.c $(pkgconf -libs -static libmosquitto libssl)

The pkgconfig file is not correct yet. I shall try to upstream the changes first.

[silabs-beta]

Indeed, I managed to build it (and found the reference to the LIBMOSQUITTO_STATIC in the API header).
Thank you for your support!

[silabs-beta]

I have just tried the patched mosquitto artifacts from here.

Probably dumb question, but why do I need to add the libssl package manually when I use static linking? When use dynamic linking, then the following build command works perfectly:
gcc basic-1.c $(pkgconf -libs -cflags libmosquitto)
But the same command with the static flag fails because of undefined reference errors.
gcc -static basic-1.c $(pkgconf -libs -cflags -static libmosquitto)

Since there is no direct dependency on libssl in basic-1.c, I think this dependency should be provided in the libmosquitto.pc file too.
Probably a Requires.private: libssl or Libs.private: -lssl entry is missing?

[Biswa96]

Probably a Requires.private: libssl or Libs.private: -lssl entry is missing?

Yes.

[silabs-beta]

What should be the way forward? Shall I open a new issue for this one? Or Shall I open a PR myself?
And what is the process of adding the fixes in the original eclipse/mosquitto repo?

[Biswa96]

I have added a new pull request to add the libssl in pkgconfig file of libmosquitto. I should have suggested the change in podsvirov's pull request. Would you like to review the new change please?

[podsvirov]

I have added a new pull request to add the libssl in pkgconfig file of libmosquitto. I should have suggested the change in podsvirov's pull request. Would you like to review the new change please?

Good addition.

[Biswa96]

Please feel free to copy or modify or upstream my changes.