1 /*
2 Example of using `externref` values.
3
4 You can build using cmake:
5
6 mkdir build && cd build && cmake .. && \
7 cmake --build . --target wasmtime-externref
8 */
9
10 #include <assert.h>
11 #include <stdio.h>
12 #include <stdlib.h>
13 #include <string.h>
14 #include <wasm.h>
15 #include <wasmtime.h>
16
17 static void exit_with_error(const char *message, wasmtime_error_t *error,
18 wasm_trap_t *trap);
19
main()20 int main() {
21 bool ok = true;
22 // Create a new configuration with Wasm reference types enabled.
23 printf("Initializing...\n");
24 wasm_config_t *config = wasm_config_new();
25 assert(config != NULL);
26 wasmtime_config_wasm_reference_types_set(config, true);
27
28 // Create an *engine*, which is a compilation context, with our configured
29 // options.
30 wasm_engine_t *engine = wasm_engine_new_with_config(config);
31 assert(engine != NULL);
32
33 // With an engine we can create a *store* which is a group of wasm instances
34 // that can interact with each other.
35 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
36 assert(store != NULL);
37 wasmtime_context_t *context = wasmtime_store_context(store);
38
39 // Read our input file, which in this case is a wasm text file.
40 FILE *file = fopen("examples/externref.wat", "r");
41 assert(file != NULL);
42 fseek(file, 0L, SEEK_END);
43 size_t file_size = ftell(file);
44 fseek(file, 0L, SEEK_SET);
45 wasm_byte_vec_t wat;
46 wasm_byte_vec_new_uninitialized(&wat, file_size);
47 if (fread(wat.data, file_size, 1, file) != 1) {
48 printf("> Error loading module!\n");
49 return 1;
50 }
51 fclose(file);
52
53 // Parse the wat into the binary wasm format
54 wasm_byte_vec_t wasm;
55 wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &wasm);
56 if (error != NULL)
57 exit_with_error("failed to parse wat", error, NULL);
58 wasm_byte_vec_delete(&wat);
59
60 // Now that we've got our binary webassembly we can compile our module.
61 printf("Compiling module...\n");
62 wasmtime_module_t *module = NULL;
63 error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module);
64 wasm_byte_vec_delete(&wasm);
65 if (error != NULL)
66 exit_with_error("failed to compile module", error, NULL);
67
68 // Instantiate the module.
69 printf("Instantiating module...\n");
70 wasm_trap_t *trap = NULL;
71 wasmtime_instance_t instance;
72 error = wasmtime_instance_new(context, module, NULL, 0, &instance, &trap);
73 if (error != NULL || trap != NULL)
74 exit_with_error("failed to instantiate", error, trap);
75
76 printf("Creating new `externref`...\n");
77
78 // Create a new `externref` value.
79 //
80 // Note that the NULL here is a finalizer callback, but we don't need one for
81 // this example.
82 wasmtime_externref_t externref;
83 ok = wasmtime_externref_new(context, "Hello, World!", NULL, &externref);
84 assert(ok);
85
86 // The `externref`'s wrapped data should be the string "Hello, World!".
87 void *data = wasmtime_externref_data(context, &externref);
88 assert(strcmp((char *)data, "Hello, World!") == 0);
89
90 wasmtime_extern_t item;
91 wasmtime_val_t externref_val;
92 externref_val.kind = WASMTIME_EXTERNREF;
93 externref_val.of.externref = externref;
94
95 // Lookup the `table` export.
96 printf("Touching `externref` table...\n");
97 {
98 ok = wasmtime_instance_export_get(context, &instance, "table",
99 strlen("table"), &item);
100 assert(ok);
101 assert(item.kind == WASMTIME_EXTERN_TABLE);
102
103 // Set `table[3]` to our `externref`.
104 error = wasmtime_table_set(context, &item.of.table, 3, &externref_val);
105 if (error != NULL)
106 exit_with_error("failed to set table", error, NULL);
107
108 // `table[3]` should now be our `externref`.
109 wasmtime_val_t elem;
110 ok = wasmtime_table_get(context, &item.of.table, 3, &elem);
111 assert(ok);
112 assert(elem.kind == WASMTIME_EXTERNREF);
113 assert(strcmp((char *)wasmtime_externref_data(context, &elem.of.externref),
114 "Hello, World!") == 0);
115 wasmtime_val_unroot(&elem);
116 }
117
118 printf("Touching `externref` global...\n");
119
120 // Lookup the `global` export.
121 {
122 ok = wasmtime_instance_export_get(context, &instance, "global",
123 strlen("global"), &item);
124 assert(ok);
125 assert(item.kind == WASMTIME_EXTERN_GLOBAL);
126
127 // Set the global to our `externref`.
128 error = wasmtime_global_set(context, &item.of.global, &externref_val);
129 if (error != NULL)
130 exit_with_error("failed to set global", error, NULL);
131
132 // Get the global, and it should return our `externref` again.
133 wasmtime_val_t global_val;
134 wasmtime_global_get(context, &item.of.global, &global_val);
135 assert(global_val.kind == WASMTIME_EXTERNREF);
136 assert(strcmp((char *)wasmtime_externref_data(context,
137 &global_val.of.externref),
138 "Hello, World!") == 0);
139 wasmtime_val_unroot(&global_val);
140 }
141
142 printf("Calling `externref` func...\n");
143
144 // Lookup the `func` export.
145 {
146 ok = wasmtime_instance_export_get(context, &instance, "func",
147 strlen("func"), &item);
148 assert(ok);
149 assert(item.kind == WASMTIME_EXTERN_FUNC);
150
151 // And call it!
152 wasmtime_val_t results[1];
153 error = wasmtime_func_call(context, &item.of.func, &externref_val, 1,
154 results, 1, &trap);
155 if (error != NULL || trap != NULL)
156 exit_with_error("failed to call function", error, trap);
157
158 // `func` returns the same reference we gave it, so `results[0]` should be
159 // our `externref`.
160 assert(results[0].kind == WASMTIME_EXTERNREF);
161 assert(strcmp((char *)wasmtime_externref_data(context,
162 &results[0].of.externref),
163 "Hello, World!") == 0);
164 wasmtime_val_unroot(&results[0]);
165 }
166 wasmtime_val_unroot(&externref_val);
167
168 // We can GC any now-unused references to our externref that the store is
169 // holding.
170 printf("GCing within the store...\n");
171 wasmtime_context_gc(context);
172
173 // Clean up after ourselves at this point
174 printf("All finished!\n");
175
176 wasmtime_store_delete(store);
177 wasmtime_module_delete(module);
178 wasm_engine_delete(engine);
179 return 0;
180 }
181
exit_with_error(const char * message,wasmtime_error_t * error,wasm_trap_t * trap)182 static void exit_with_error(const char *message, wasmtime_error_t *error,
183 wasm_trap_t *trap) {
184 fprintf(stderr, "error: %s\n", message);
185 wasm_byte_vec_t error_message;
186 if (error != NULL) {
187 wasmtime_error_message(error, &error_message);
188 wasmtime_error_delete(error);
189 } else {
190 wasm_trap_message(trap, &error_message);
191 wasm_trap_delete(trap);
192 }
193 fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data);
194 wasm_byte_vec_delete(&error_message);
195 exit(1);
196 }
197