1 /* 2 Example of instantiating of the WebAssembly module and invoking its exported 3 function. 4 5 You can compile and run this example on Linux with: 6 7 cargo build --release -p wasmtime-c-api 8 cc examples/gcd.c \ 9 -I crates/c-api/include \ 10 -I crates/c-api/wasm-c-api/include \ 11 target/release/libwasmtime.a \ 12 -lpthread -ldl -lm \ 13 -o gcd 14 ./gcd 15 16 Note that on Windows and macOS the command will be similar, but you'll need 17 to tweak the `-lpthread` and such annotations. 18 19 You can also build using cmake: 20 21 mkdir build && cd build && cmake .. && cmake --build . --target wasmtime-gcd 22 */ 23 24 #include <assert.h> 25 #include <stdio.h> 26 #include <stdlib.h> 27 #include <wasm.h> 28 #include <wasmtime.h> 29 30 static void exit_with_error(const char *message, wasmtime_error_t *error, 31 wasm_trap_t *trap); 32 33 int main() { 34 int ret = 0; 35 // Set up our context 36 wasm_engine_t *engine = wasm_engine_new(); 37 assert(engine != NULL); 38 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL); 39 assert(store != NULL); 40 wasmtime_context_t *context = wasmtime_store_context(store); 41 42 // Load our input file to parse it next 43 FILE *file = fopen("examples/gcd.wat", "r"); 44 if (!file) { 45 printf("> Error loading file!\n"); 46 return 1; 47 } 48 fseek(file, 0L, SEEK_END); 49 size_t file_size = ftell(file); 50 fseek(file, 0L, SEEK_SET); 51 wasm_byte_vec_t wat; 52 wasm_byte_vec_new_uninitialized(&wat, file_size); 53 if (fread(wat.data, file_size, 1, file) != 1) { 54 printf("> Error loading module!\n"); 55 return 1; 56 } 57 fclose(file); 58 59 // Parse the wat into the binary wasm format 60 wasm_byte_vec_t wasm; 61 wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &wasm); 62 if (error != NULL) 63 exit_with_error("failed to parse wat", error, NULL); 64 wasm_byte_vec_delete(&wat); 65 66 // Compile and instantiate our module 67 wasmtime_module_t *module = NULL; 68 error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module); 69 if (module == NULL) 70 exit_with_error("failed to compile module", error, NULL); 71 wasm_byte_vec_delete(&wasm); 72 73 wasm_trap_t *trap = NULL; 74 wasmtime_instance_t instance; 75 error = wasmtime_instance_new(context, module, NULL, 0, &instance, &trap); 76 if (error != NULL || trap != NULL) 77 exit_with_error("failed to instantiate", error, trap); 78 79 // Lookup our `gcd` export function 80 wasmtime_extern_t gcd; 81 bool ok = wasmtime_instance_export_get(context, &instance, "gcd", 3, &gcd); 82 assert(ok); 83 assert(gcd.kind == WASMTIME_EXTERN_FUNC); 84 85 // And call it! 86 int a = 6; 87 int b = 27; 88 wasmtime_val_t params[2]; 89 params[0].kind = WASMTIME_I32; 90 params[0].of.i32 = a; 91 params[1].kind = WASMTIME_I32; 92 params[1].of.i32 = b; 93 wasmtime_val_t results[1]; 94 error = 95 wasmtime_func_call(context, &gcd.of.func, params, 2, results, 1, &trap); 96 if (error != NULL || trap != NULL) 97 exit_with_error("failed to call gcd", error, trap); 98 assert(results[0].kind == WASMTIME_I32); 99 100 printf("gcd(%d, %d) = %d\n", a, b, results[0].of.i32); 101 102 // Clean up after ourselves at this point 103 ret = 0; 104 105 wasmtime_module_delete(module); 106 wasmtime_store_delete(store); 107 wasm_engine_delete(engine); 108 return ret; 109 } 110 111 static void exit_with_error(const char *message, wasmtime_error_t *error, 112 wasm_trap_t *trap) { 113 fprintf(stderr, "error: %s\n", message); 114 wasm_byte_vec_t error_message; 115 if (error != NULL) { 116 wasmtime_error_message(error, &error_message); 117 } else { 118 wasm_trap_message(trap, &error_message); 119 } 120 fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data); 121 wasm_byte_vec_delete(&error_message); 122 exit(1); 123 } 124