Libsodium on macOS, undefined symbols for x86_64 - c

Question

I'm using an Intel Mac running Catalina 10.15.1
I'm trying to use libsodium using gcc Apple clang version 11.0.0 (clang-1100.0.33.12)
I have both tried to install libsodium via home-brew and manually compile (which was successful), however, when trying to use libsodium I get this error:
Undefined symbols for architecture x86_64:
"_crypto_generichash", referenced from:
_main in sodium-ae2fd0.o
"_sodium_init", referenced from:
_main in sodium-ae2fd0.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
This is the basic code, using libsodium: stable 1.0.18 (bottled), HEAD
1 #include <sodium.h>
2
3 int main(void)
4 {
5
6 sodium_init();
7
8 #define MESSAGE ((const unsigned char *) "Arbitrary data to hash")
9 #define MESSAGE_LEN 22
10
11 unsigned char hash[crypto_generichash_BYTES];
12
13 crypto_generichash(hash, sizeof hash,
14 MESSAGE, MESSAGE_LEN,
15 NULL, 0);
16
17 return 0;
18 }
Any ideas?

Answer 1

The issue is probably not in the libsodium installation, but in the way your example application is compiled.
In order to link a library (besides the C library which is implicitly linked) when compiling a C program, you need to add the -l<library name> flag to the compilation command line:
cc -Wall -W -o example example.c -lsodium