demo

test/shared_library_unwind/BUILD.bazel

@@ -0,0 +1,40 @@
+load("@rules_cc//cc:defs.bzl", "cc_test")
+load("@rules_rs//rs:rust_shared_library.bzl", "rust_shared_library")
+load("@rules_shell//shell:sh_test.bzl", "sh_test")
+
+_LINUX_ONLY = select({
+    "@platforms//os:linux": [],
+    "//conditions:default": ["@platforms//:incompatible"],
+})
+
+rust_shared_library(
+    name = "filewatcher_jni",
+    srcs = ["filewatcher_jni.rs"],
+    crate_name = "filewatcher_jni",
+    edition = "2021",
+)
+
+sh_test(
+    name = "filewatcher_jni_unwind_link_test",
+    srcs = ["unwind_link_test.sh"],
+    args = [
+        "$(location :filewatcher_jni)",
+        "$(location @llvm//tools:llvm-nm)",
+        "$(location @llvm//tools:llvm-readelf)",
+    ],
+    data = [
+        ":filewatcher_jni",
+        "@llvm//tools:llvm-nm",
+        "@llvm//tools:llvm-readelf",
+    ],
+    target_compatible_with = _LINUX_ONLY,
+)
+
+cc_test(
+    name = "filewatcher_jni_dlopen_test",
+    srcs = ["dlopen_test.c"],
+    args = ["$(location :filewatcher_jni)"],
+    data = [":filewatcher_jni"],
+    linkopts = ["-ldl"],
+    target_compatible_with = _LINUX_ONLY,
+)

test/shared_library_unwind/dlopen_test.c

@@ -0,0 +1,24 @@
+#include <dlfcn.h>
+#include <stdio.h>
+
+int main(int argc, char **argv) {
+    if (argc != 2) {
+        fprintf(stderr, "usage: %s <shared-library>\n", argv[0]);
+        return 2;
+    }
+
+    void *handle = dlopen(argv[1], RTLD_NOW | RTLD_LOCAL);
+    if (!handle) {
+        fprintf(stderr, "dlopen failed: %s\n", dlerror());
+        return 1;
+    }
+
+    if (!dlsym(handle, "Java_com_example_FileWatcher_nativeInit")) {
+        fprintf(stderr, "dlsym failed: %s\n", dlerror());
+        dlclose(handle);
+        return 1;
+    }
+
+    dlclose(handle);
+    return 0;
+}

test/shared_library_unwind/filewatcher_jni.rs

@@ -0,0 +1,13 @@
+use std::ffi::c_void;
+
+unsafe extern "C" {
+    fn _Unwind_GetIP(ctx: *mut c_void) -> usize;
+    fn _Unwind_GetIPInfo(ctx: *mut c_void, ip_before_insn: *mut i32) -> usize;
+}
+
+#[no_mangle]
+pub extern "C" fn Java_com_example_FileWatcher_nativeInit() -> usize {
+    let get_ip = _Unwind_GetIP as usize;
+    let get_ip_info = _Unwind_GetIPInfo as usize;
+    get_ip ^ get_ip_info
+}

test/shared_library_unwind/unwind_link_test.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+lib="$1"
+llvm_nm="$2"
+llvm_readelf="$3"
+
+undefined="$("$llvm_nm" -m -u "$lib")"
+echo "$undefined" | grep '_Unwind_GetIP$'
+echo "$undefined" | grep '_Unwind_GetIPInfo$'
+
+dynamic="$("$llvm_readelf" --dynamic "$lib")"
+echo "$dynamic" | grep 'Shared library: \[libunwind\.so'
+echo "$dynamic" | grep 'RUNPATH'