Fix static builds

[gjedeer]

I'm porting tuntox to work with TokTok c-toxcore and couldn't get it to link statically - dynamic linking works.

I'm not sure if the solution in this pull request is valid but it definitely makes the static linking work.

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This change is 

[iphydf]

I don't know if this is correct, either. What does Libs.private do?

[gjedeer]

From man pkg-config:

Libs.private:

This line should list any private libraries in use. Private libraries are libraries which are not exposed through your library, but are needed in the case of static linking. This differs from Requires.private in that it references libraries that do not have package files installed.

[GrayHatter]

@gjedeer I'd like to see the error output you're getting. Just to be sure this is our problem, and not how you're building.

That said, after reading this https://autotools.io/pkgconfig/dependencies.html#pkgconfig.static-link It makes me think that adding the same libs to Libs.Private just causes pkg-config to recursively search through the required libs to make sure that everything is supplied to the compiler. That leads me to two conclusions. 1) This shouldn't be harmful, and 2) if adding this to your build script fixes the issue; you're not including the correct deps for tuntox yourself.

+@GrayHatter

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Review status: 0 of 1 files reviewed at latest revision, all discussions resolved, some commit checks broke.

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Comments from Reviewable

[gjedeer]

The Makefile is as simple as they come.

With the Libs.private change, the linker is executed like this:

gcc -o tuntox client.o log.o gitversion.o mach.o main.o util.o -lpthread -g -pthread -lm -static -lrt -L/usr/local/lib -lpthread -lrt -ltoxcrypto -ltoxnetwork -ltoxdht -ltoxnetcrypto -ltoxfriends -ltoxmessenger -ltoxgroup -ltoxcore -lpthread -lrt -ltoxcrypto -ltoxnetwork -ltoxdht -ltoxnetcrypto -ltoxfriends -ltoxmessenger -ltoxgroup -ltoxcore -lsodium

and pkg-config outputs as following:

➜  ~ pkg-config --cflags libsodium toxcore       
-I/usr/local/include
➜  ~ pkg-config --static --libs libsodium toxcore
-L/usr/local/lib -lpthread -lrt -ltoxcrypto -ltoxnetwork -ltoxdht -ltoxnetcrypto -ltoxfriends -ltoxmessenger -ltoxgroup -ltoxcore -lpthread -lrt -ltoxcrypto -ltoxnetwork -ltoxdht -ltoxnetcrypto -ltoxfriends -ltoxmessenger -ltoxgroup -ltoxcore -lsodium

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Without Libs.private:

gcc -o tuntox client.o log.o gitversion.o mach.o main.o util.o -lpthread -g -pthread -lm -static -lrt -L/usr/local/lib -lpthread -lrt -ltoxcrypto -ltoxnetwork -ltoxdht -ltoxnetcrypto -ltoxfriends -ltoxmessenger -ltoxgroup -ltoxcore -lsodium

and pkg-config outputs as following:

➜  ~ pkg-config --cflags libsodium toxcore
-I/usr/local/include
➜  ~ pkg-config --static --libs libsodium toxcore
-L/usr/local/lib -lpthread -lrt -ltoxcrypto -ltoxnetwork -ltoxdht -ltoxnetcrypto -ltoxfriends -ltoxmessenger -ltoxgroup -ltoxcore -lsodium

The former links correctly, the latter yields a stream of errors starting with:

/usr/local/lib/libtoxcore.a(tox.c.o): In function `tox_new':
tox.c:(.text+0x63d): undefined reference to `ip_init'
tox.c:(.text+0x669): undefined reference to `addr_resolve_or_parse_ip'
tox.c:(.text+0x6b1): undefined reference to `new_messenger'
tox.c:(.text+0x6c1): undefined reference to `new_groupchats'
tox.c:(.text+0x6d2): undefined reference to `kill_messenger'
tox.c:(.text+0x74a): undefined reference to `messenger_load'
tox.c:(.text+0x783): undefined reference to `load_secret_key'
/usr/local/lib/libtoxcore.a(tox.c.o): In function `tox_kill':
tox.c:(.text+0x7ef): undefined reference to `kill_groupchats'
tox.c:(.text+0x7fb): undefined reference to `kill_messenger'
......

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I have no idea what makes my change work with --static, it's the same output but all -l flags are duplicated.

[gjedeer]

Can it be that the order of -l flags is wrong and that's why duplication resolves the build (but if that's the case, why does the dynamic build work?)

[gjedeer]

The typical UNIX linker works from left to right, so put all your dependent libraries on the left, and the ones that satisfy those dependencies on the right of the link line. You may find that some libraries depend on others while at the same time other libraries depend on them. This is where it gets complicated.

sauce

[gjedeer]

Sorry for flooding but I resolved this in a much simpler way: moving -ltoxcore to the front. Updated PR accordingly.

[iphydf]

Can you rebase this on master?

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Review status: 0 of 2 files reviewed at latest revision, all discussions resolved, some commit checks failed.

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Comments from Reviewable

[gjedeer]

Done

[nurupo]

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Reviewed 2 of 2 files at r1.
Review status: all files reviewed at latest revision, all discussions resolved, all commit checks successful.

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Comments from Reviewable