CODEWITHSUNDEEP
clinker
Dinesh
Dinesh

Reputation: 111

GNU build system question

How to find the library, which contains the definition of particular function? I am getting linker error.

Upvotes: 6

Views: 145

Answers (3)

P Shved
P Shved

Reputation: 99384

If you want to find out the library in non-programmatical way, you might find LSB Navigator useful. Enter the function into the search box, and check the library in the line with green "status".


(source: coldattic.info)

This will be the "conventional" library that contains the function (in the example depicted above, librt is the correct library for mq_unlink, so you link with -lrt). Just link with that library, and it will work on virtually all Linux systems.

Note: I was one of the developers of the tool I recommend.

Upvotes: 1

unwind
unwind

Reputation: 400109

You can use the nm command-line tool to list exported symbols in binaries:

~/src> cat nm-test.c

static int plus_four(int x)
{
        return x + 4;
}

int sum_plus_four(int a, int b)
{
        return plus_four(a + b);
}

int product_plus_four(int a, int b)
{
        return plus_four(a * b);
}
~/src> gcc -c nm-test.c
~/src> nm ./nm-test.o
00000000 t plus_four
00000023 T product_plus_four
0000000b T sum_plus_four

According to the manual, 't' means that the symbol is in the code (text) segment, and uppercase means it's public.

If you have a symbol that you're looking for, you can use nm to make the symbols exported by a library accessible to e.g. grep:

$ find -name lib*.a /example/library/path | xargs nm | grep -E "T $SYMBOL_TO_FIND"

This command-line is an untested sketch, but it should show the concept.

Upvotes: 4

Yuval Adam
Yuval Adam

Reputation: 165340

If it's part of the C standard API then just run man, it should clearly state where the function is defined.

Upvotes: 1

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