samples/native-lib: Add an example to use wamr API from native lib (#1649)

Real world native libs likely need to access the wasm_runtime_xxx API.
This example demonstrates it.

Build vmlib as a shared lib to make it straightforward to share a
single runtime instance between iwasm and native libs.

samples/native-lib/CMakeLists.txt

@@ -58,7 +58,9 @@ set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra -Wformat -Wformat-security")
 set (WAMR_ROOT_DIR ${CMAKE_CURRENT_LIST_DIR}/../..)
 include (${WAMR_ROOT_DIR}/build-scripts/runtime_lib.cmake)
 
-add_library(vmlib ${WAMR_RUNTIME_LIB_SOURCE})
+# Note: we build vmlib as a shared library here so that it can be
+# shared between iwasm and native libraries.
+add_library(vmlib SHARED ${WAMR_RUNTIME_LIB_SOURCE})
 
 ################ wamr runtime ###################
 include (${SHARED_DIR}/utils/uncommon/shared_uncommon.cmake)
@@ -79,6 +81,10 @@ target_link_libraries(iwasm vmlib -lpthread -lm -ldl)
 add_library (test_add SHARED test_add.c)
 add_library (test_sqrt SHARED test_sqrt.c)
 add_library (test_hello SHARED test_hello.c)
+# Note: Unlike simpler examples above, test_hello2 directly uses
+# the API provided by the vmlib library.
+add_library (test_hello2 SHARED test_hello2.c)
+target_link_libraries(test_hello2 vmlib)
 
 ################ wasm application ###############
 add_subdirectory(wasm-app)

samples/native-lib/README.md

@@ -49,14 +49,14 @@ will be generated.
 
 ```bash
 cd build
-./iwasm --native-lib=./libtest_add.so --native-lib=./libtest_sqrt.so --native-lib=./libtest_hello.so wasm-app/test.wasm
+./iwasm --native-lib=./libtest_add.so --native-lib=./libtest_sqrt.so --native-lib=./libtest_hello.so --native-lib=./libtest_hello2.so wasm-app/test.wasm
 ```
 
 ### macOS
 
 ```bash
 cd build
-./iwasm --native-lib=libtest_add.dylib --native-lib=libtest_sqrt.dylib --native-lib=libtest_hello.dylib wasm-app/test.wasm
+./iwasm --native-lib=libtest_add.dylib --native-lib=libtest_sqrt.dylib --native-lib=libtest_hello.dylib --native-lib=libtest_hello2.dylib wasm-app/test.wasm
 ```
 
 The output is:
@@ -66,7 +66,11 @@ Hello World!
 10 + 20 = 30
 sqrt(10, 20) = 500
 test_hello("main", 0x0, 0) = 41
-malloc(42) = 0x24b8
-test_hello("main", 0x24b8, 42) = 41
+malloc(42) = 0x24e8
+test_hello("main", 0x24e8, 42) = 41
 Message from test_hello: Hello, main. This is test_hello_wrapper!
+test_hello2("main", 0x0, 0) = 85
+malloc(86) = 0x24e8
+test_hello2("main", 0x24e8, 86) = 85
+Message from test_hello2: Hello, main. This is test_hello2_wrapper! Your wasm_module_inst_t is 0x7fd443704990.
 ```

samples/native-lib/test_hello2.c

@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+/*
+ * This example basically does the same thing as test_hello.c,
+ * using wasm_export.h API.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "wasm_export.h"
+
+static int
+test_hello2_wrapper(wasm_exec_env_t exec_env, uint32_t nameaddr,
+                    uint32_t resultaddr, uint32_t resultlen)
+{
+    /*
+     * Perform wasm_runtime_malloc to check if the runtime has been
+     * initialized as expected.
+     * This would fail with "memory hasn't been initialize" error
+     * unless we are not sharing a runtime with the loader app. (iwasm)
+     */
+    void *p = wasm_runtime_malloc(1);
+    if (p == NULL) {
+        return -1;
+    }
+    wasm_runtime_free(p);
+
+    wasm_module_inst_t inst = wasm_runtime_get_module_inst(exec_env);
+    if (!wasm_runtime_validate_app_str_addr(inst, nameaddr)
+        || !wasm_runtime_validate_app_addr(inst, resultaddr, resultlen)) {
+        return -1;
+    }
+    const char *name = wasm_runtime_addr_app_to_native(inst, nameaddr);
+    char *result = wasm_runtime_addr_app_to_native(inst, resultaddr);
+    return snprintf(result, resultlen,
+                    "Hello, %s. This is %s! Your wasm_module_inst_t is %p.\n",
+                    name, __func__, inst);
+}
+
+/* clang-format off */
+#define REG_NATIVE_FUNC(func_name, signature) \
+    { #func_name, func_name##_wrapper, signature, NULL }
+
+static NativeSymbol native_symbols[] = {
+    REG_NATIVE_FUNC(test_hello2, "(iii)i")
+};
+/* clang-format on */
+
+uint32_t
+get_native_lib(char **p_module_name, NativeSymbol **p_native_symbols)
+{
+    *p_module_name = "env";
+    *p_native_symbols = native_symbols;
+    return sizeof(native_symbols) / sizeof(NativeSymbol);
+}

samples/native-lib/wasm-app/main.c

@@ -15,6 +15,9 @@ test_sqrt(int x, int y);
 int
 test_hello(const char *name, char *buf, size_t buflen);
 
+int
+test_hello2(const char *name, char *buf, size_t buflen);
+
 int
 main(int argc, char **argv)
 {
@@ -33,12 +36,35 @@ main(int argc, char **argv)
 
     res = test_hello(name, NULL, 0);
     printf("test_hello(\"%s\", %p, %zu) = %d\n", name, NULL, (size_t)0, res);
+    if (res == -1) {
+        return -1;
+    }
     buflen = res + 1;
     buf = malloc(buflen);
     printf("malloc(%zu) = %p\n", buflen, buf);
     res = test_hello(__func__, buf, buflen);
+    if (res == -1) {
+        return -1;
+    }
     printf("test_hello(\"%s\", %p, %zu) = %d\n", name, buf, buflen, res);
     printf("Message from test_hello: %s", buf);
+    free(buf);
+
+    res = test_hello2(name, NULL, 0);
+    printf("test_hello2(\"%s\", %p, %zu) = %d\n", name, NULL, (size_t)0, res);
+    if (res == -1) {
+        return -1;
+    }
+    buflen = res + 1;
+    buf = malloc(buflen);
+    printf("malloc(%zu) = %p\n", buflen, buf);
+    res = test_hello2(__func__, buf, buflen);
+    if (res == -1) {
+        return -1;
+    }
+    printf("test_hello2(\"%s\", %p, %zu) = %d\n", name, buf, buflen, res);
+    printf("Message from test_hello2: %s", buf);
+    free(buf);
 
     return 0;
 }