jasonsewall / rust-lib-extra-symbols

Extra unused symbols in rust library

If we include lib1 as a dep, and use something from it, like a data structure, we find that the resulting cdylib contains the function foo from lib1 even though it is not used.

$ cd lib2/
$ cargo build -r
$ nm -D target/release/liblib2.so
0000000000001100 T bar
                 w __cxa_finalize@GLIBC_2.2.5
0000000000001100 T foo
                 w __gmon_start__
                 w _ITM_deregisterTMCloneTable
                 w _ITM_registerTMCloneTable

If we comment out the use line in lib2/src/lib.rs, we find that foo is not exported.

$ set -i 's/use/\/\/use/' src/lib.rs
$ cargo build -r
$ nm -D target/release/liblib2.so
0000000000001100 T bar
                 w __cxa_finalize@GLIBC_2.2.5
                 w __gmon_start__
                 w _ITM_deregisterTMCloneTable
                 w _ITM_registerTMCloneTable

Why does this happen?