CODEWITHSUNDEEP
linuxgccshared-libraries
Mark Galeck
Mark Galeck

Reputation: 6385

how is it possible for shared library to define a function but can't link to it?

How is this possible:

>nm --defined-only foobar.so | grep foobar
000000000003c7c0 t foobar
>gcc foobar.c foobar.so
foobar.c:(.text+0x19): undefined reference to `foobar'
collect2: ld returned 1 exit status

Upvotes: 0

Views: 212

Answers (2)

Severin Pappadeux
Severin Pappadeux

Reputation: 20080

On top of excellent @Tibrogargan answer, you may try to check binding using readelf utility, it is a bit more clear wrt global vs local symbols - it will actually print GLOBAL or LOCAL

> readelf --symbols foobar.so

Upvotes: 0

Tibrogargan
Tibrogargan

Reputation: 4603

You can't link to "foobar" because foobar.so defines "foobar" as a local symbol in the "text" area and only global symbols are exported

The 2nd column of the output of nm gives the symbol type. lowercase means local, uppercase means global. Only global symbols are exported. See man nm(1)

Upvotes: 1

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