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/*
Example of instantiating of the WebAssembly module and invoking its exported
function.
You can compile and run this example on Linux with:
cargo build --release -p wasmtime-c-api
cc examples/interrupt.c \
-I crates/c-api/include \
target/release/libwasmtime.a \
-lpthread -ldl -lm \
-o interrupt
./interrupt
Note that on Windows and macOS the command will be similar, but you'll need
to tweak the `-lpthread` and such annotations as well as the name of the
`libwasmtime.a` file on Windows.
You can also build using cmake:
mkdir build && cd build && cmake .. && \
cmake --build . --target wasmtime-interrupt
*/
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <wasm.h>
#include <wasmtime.h>
#ifdef _WIN32
static void spawn_interrupt(wasm_engine_t *engine) {
wasmtime_engine_increment_epoch(engine);
}
#else
#include <pthread.h>
#include <time.h>
static void *helper(void *_engine) {
wasm_engine_t *engine = _engine;
struct timespec sleep_dur;
sleep_dur.tv_sec = 1;
sleep_dur.tv_nsec = 0;
nanosleep(&sleep_dur, NULL);
printf("Sending an interrupt\n");
wasmtime_engine_increment_epoch(engine);
return 0;
}
static void spawn_interrupt(wasm_engine_t *engine) {
pthread_t child;
int rc = pthread_create(&child, NULL, helper, engine);
assert(rc == 0);
}
#endif
static void exit_with_error(const char *message, wasmtime_error_t *error,
wasm_trap_t *trap);
int main() {
// Create a `wasm_store_t` with interrupts enabled
wasm_config_t *config = wasm_config_new();
assert(config != NULL);
wasmtime_config_epoch_interruption_set(config, true);
wasm_engine_t *engine = wasm_engine_new_with_config(config);
assert(engine != NULL);
wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
assert(store != NULL);
wasmtime_context_t *context = wasmtime_store_context(store);
// Configure the epoch deadline after which WebAssembly code will trap.
wasmtime_context_set_epoch_deadline(context, 1);
// Read our input file, which in this case is a wasm text file.
FILE *file = fopen("examples/interrupt.wat", "r");
assert(file != NULL);
fseek(file, 0L, SEEK_END);
size_t file_size = ftell(file);
fseek(file, 0L, SEEK_SET);
wasm_byte_vec_t wat;
wasm_byte_vec_new_uninitialized(&wat, file_size);
if (fread(wat.data, file_size, 1, file) != 1) {
printf("> Error loading module!\n");
return 1;
}
fclose(file);
// Parse the wat into the binary wasm format
wasm_byte_vec_t wasm;
wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &wasm);
if (error != NULL)
exit_with_error("failed to parse wat", error, NULL);
wasm_byte_vec_delete(&wat);
// Now that we've got our binary webassembly we can compile our module.
wasmtime_module_t *module = NULL;
error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module);
wasm_byte_vec_delete(&wasm);
if (error != NULL)
exit_with_error("failed to compile module", error, NULL);
wasm_trap_t *trap = NULL;
wasmtime_instance_t instance;
error = wasmtime_instance_new(context, module, NULL, 0, &instance, &trap);
if (error != NULL || trap != NULL)
exit_with_error("failed to instantiate", error, trap);
wasmtime_module_delete(module);
// Lookup our `run` export function
wasmtime_extern_t run;
bool ok = wasmtime_instance_export_get(context, &instance, "run", 3, &run);
assert(ok);
assert(run.kind == WASMTIME_EXTERN_FUNC);
// Spawn a thread to send us an interrupt after a period of time.
spawn_interrupt(engine);
// And call it!
printf("Entering infinite loop...\n");
error = wasmtime_func_call(context, &run.of.func, NULL, 0, NULL, 0, &trap);
assert(error == NULL);
assert(trap != NULL);
printf("Got a trap!...\n");
wasmtime_store_delete(store);
wasm_engine_delete(engine);
return 0;
}
static void exit_with_error(const char *message, wasmtime_error_t *error,
wasm_trap_t *trap) {
fprintf(stderr, "error: %s\n", message);
wasm_byte_vec_t error_message;
if (error != NULL) {
wasmtime_error_message(error, &error_message);
wasmtime_error_delete(error);
} else {
wasm_trap_message(trap, &error_message);
wasm_trap_delete(trap);
}
fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data);
wasm_byte_vec_delete(&error_message);
exit(1);
}
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