Fix linking against versioned shared library

.bazelci/presubmit.yml

@@ -1,24 +1,28 @@
 ---
-default_targets: &default_targets
+default_linux_targets: &default_linux_targets
 - "--" # Allows negative patterns; hack for https://github.com/bazelbuild/continuous-integration/pull/245
 - "..."
 - "@examples//..."
+# TODO: Switch manual tag to platform constraint after bazel 4.0.
+- "//test/versioned_dylib:versioned_dylib_test"
 # Bindgen currently only has a working toolchain for 18.04
 - "-@examples//ffi/rust_calling_c/simple/..."
 tasks:
   ubuntu1604:
-    build_targets: *default_targets
-    test_targets: *default_targets
+    build_targets: *default_linux_targets
+    test_targets: *default_linux_targets
   ubuntu1804:
-    build_targets: *default_targets
+    build_targets: *default_linux_targets
     test_targets:
       - "..."
       - "@examples//..."
+      # TODO: Switch manual tag to platform constraint after bazel 4.0.
+      - "//test/versioned_dylib:versioned_dylib_test"
   ubuntu2004:
     name: "Minimum Supported Version"
     bazel: "3.0.0"
-    build_targets: *default_targets
-    test_targets: *default_targets
+    build_targets: *default_linux_targets
+    test_targets: *default_linux_targets
   macos:
     osx_targets: &osx_targets
     - "--" # Allows negative patterns; hack for https://github.com/bazelbuild/continuous-integration/pull/245

rust/private/rustc.bzl

@@ -185,7 +185,8 @@ def collect_deps(label, deps, proc_macro_deps, aliases, toolchain):
             transitive_dylibs.append(depset([
                 lib
                 for lib in libs.to_list()
-                if lib.basename.endswith(toolchain.dylib_ext)
+                # Dynamic libraries may have a version number nowhere, or before (linux) or after (macos) the extension.
+                if lib.basename.endswith(toolchain.dylib_ext) or lib.basename.split(".", 2)[1] == toolchain.dylib_ext[1:]
             ]))
             transitive_staticlibs.append(depset([
                 lib

rust/private/utils.bzl

@@ -77,7 +77,8 @@ def get_lib_name(lib):
     Returns:
         str: The name of the library
     """
-    libname, ext = lib.basename.split(".", 2)
+    # NB: The suffix may contain a version number like 'so.1.2.3'
+    libname = lib.basename.split(".", 1)[0]
 
     if libname.startswith("lib"):
         return libname[3:]

test/versioned_dylib/BUILD

@@ -0,0 +1,25 @@
+load(
+    "@io_bazel_rules_rust//rust:rust.bzl",
+    "rust_binary",
+    "rust_test",
+)
+
+package(default_visibility = ["//visibility:public"])
+
+rust_binary(
+    name = "versioned_dylib",
+    srcs = [
+        "src/main.rs",
+    ],
+    tags = ["manual"],
+    deps = [
+        "//test/versioned_dylib/c:libreturn_zero",
+        "@libc",
+    ],
+)
+
+rust_test(
+    name = "versioned_dylib_test",
+    crate = "versioned_dylib",
+    tags = ["manual"],
+)

test/versioned_dylib/c/BUILD

@@ -0,0 +1,23 @@
+load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library")
+
+[cc_binary(
+    name = "libreturn_zero." + x,
+    srcs = [
+        "return_zero.c",
+        "return_zero.h",
+    ],
+    copts = ["-std=c99"],
+    linkopts = ["-Wl,-soname,libreturn_zero.so.2"],
+    linkshared = True,
+    tags = ["manual"],
+) for x in ("so", "so.2")]
+
+cc_library(
+    name = "libreturn_zero",
+    srcs = [
+        ":libreturn_zero.so",
+        ":libreturn_zero.so.2",
+    ],
+    tags = ["manual"],
+    visibility = ["//visibility:public"],
+)

test/versioned_dylib/c/return_zero.c

@@ -0,0 +1,5 @@
+#include "return_zero.h"
+
+int return_zero() {
+    return 0;
+}

test/versioned_dylib/c/return_zero.h

@@ -0,0 +1,6 @@
+#ifndef versioned_lib_h__
+#define versioned_lib_h__
+
+extern int return_zero();
+
+#endif  // versioned_lib_h__

test/versioned_dylib/src/main.rs

@@ -0,0 +1,38 @@
+// Copyright 2020 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+extern crate libc;
+
+extern {
+    pub fn return_zero() -> libc::c_int;
+}
+
+fn main() {
+    let zero = unsafe { return_zero() };
+    println!("Got {} from our shared lib", zero);
+}
+
+
+#[cfg(test)]
+mod test {
+    extern {
+        pub fn return_zero() -> libc::c_int;
+    }
+
+    #[test]
+    fn test_return_zero() {
+        assert_eq!(0, unsafe { return_zero() });
+        // If we make it past this call, it linked correctly, so the test passes.
+    }
+}