Can't be included in a dylib type crate

[JakeBecker]

Tested on Mac OS Sierra. Including parquet as a dependency in a crate with

[lib]
crate-type = ["dylib"]

Causes the linker to fail:

error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-m64" "-L" "/Users/jakebecker/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib" [really long command omitted]

  = note: duplicate symbol _XXH64_digest in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH32_digest in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH64_reset in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH32_reset in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH_versionNumber in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH64_hashFromCanonical in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH32_hashFromCanonical in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH64_canonicalFromHash in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH32_canonicalFromHash in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH64_copyState in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH32_copyState in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH64_createState in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH32_createState in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH64_freeState in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH32_freeState in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH64_update in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH32_update in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH64 in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          duplicate symbol _XXH32 in:
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/libzstd_sys-7acf92beb8282696.rlib(xxhash.o)
              /var/folders/ff/stmyfx1s5yqg_0pl1fq6cft80000gn/T/rustcfOjx4t/liblz4_sys-e1d5bb1cebde788e.rlib(xxhash.o)
          ld: 19 duplicate symbols for architecture x86_64
          clang: error: linker command failed with exit code 1 (use -v to see invocation)

It appears that both libzstd and liblz4 include the C library xxhash, and this causes the duplicate symbol error.

[sunchao]

Thanks for reporting this @JakeBecker . Not very familiar with dylib myself but will take a look at the duplicated symbol error.