Prompt interface and bug fixes

Makefile

@@ -4,9 +4,9 @@ WASMFX_CONT_TABLE_INITIAL_CAPACITY?=1024
 WASMFX_PRESERVE_SHADOW_STACK?=1
 # Only relevant if WASMFX_PRESERVE_SHADOW_STACK is 1
 WASMFX_CONT_SHADOW_STACK_SIZE?=65536
-ASYNCIFY=../binaryen/bin/wasm-opt --enable-exception-handling --enable-reference-types --enable-multivalue --enable-bulk-memory --enable-gc --enable-stack-switching -O2 --asyncify
+ASYNCIFY=../binaryen/bin/wasm-opt --enable-exception-handling --enable-reference-types --enable-multivalue --enable-bulk-memory --enable-gc --enable-stack-switching -O2 -g --asyncify --no-inline="fiber_yield,fiber_yield_to,fiber_resume,fiber_resume_with"
 WASICC=../benchfx/wasi-sdk-22.0/bin/clang
-WASIFLAGS=--sysroot=../benchfx/wasi-sdk-22.0/share/wasi-sysroot -std=c17 -Wall -Wextra -Werror -Wpedantic -Wno-strict-prototypes -O3 -I inc
+WASIFLAGS=-g --sysroot=../benchfx/wasi-sdk-22.0/share/wasi-sysroot -std=c17 -Wall -Wextra -Werror -Wpedantic -Wno-strict-prototypes -O0 -I inc
 WASM_INTERP=../spec/interpreter/wasm
 WASM_MERGE=../binaryen/bin/wasm-merge --enable-multimemory --enable-exception-handling --enable-reference-types --enable-multivalue --enable-bulk-memory --enable-gc --enable-stack-switching
 
@@ -20,7 +20,7 @@ endif
 all: hello sieve itersum treesum
 
 .PHONY: hello
-hello: hello_asyncify.wasm hello_wasmfx.wasm
+hello: hello_asyncify.wasm hello_wasmfx.wasm hello_prompt_asyncify.wasm hello_forward_prompt_asyncify.wasm
 
 hello_asyncify.wasm: inc/fiber.h src/asyncify/asyncify_impl.c examples/hello.c
 	$(WASICC) -DSTACK_POOL_SIZE=$(STACK_POOL_SIZE) -DASYNCIFY_DEFAULT_STACK_SIZE=$(ASYNCIFY_DEFAULT_STACK_SIZE) src/asyncify/asyncify_impl.c $(WASIFLAGS) examples/hello.c -o hello_asyncfiy.pre.wasm
@@ -33,6 +33,17 @@ hello_wasmfx.wasm: inc/fiber.h src/wasmfx/imports.wat src/wasmfx/wasmfx_impl.c e
 	$(WASM_MERGE) fiber_wasmfx_imports.wasm "fiber_wasmfx_imports" hello_wasmfx.pre.wasm "main" -o hello_wasmfx.wasm
 	chmod +x hello_wasmfx.wasm
 
+hello_prompt_asyncify.wasm: inc/fiber.h src/asyncify/asyncify_prompt_impl.c examples/prompt/hello.c
+	$(WASICC) -DSTACK_POOL_SIZE=$(STACK_POOL_SIZE) -DASYNCIFY_DEFAULT_STACK_SIZE=$(ASYNCIFY_DEFAULT_STACK_SIZE) src/asyncify/asyncify_prompt_impl.c $(WASIFLAGS) examples/prompt/hello.c -o hello_prompt_asyncfiy.pre.wasm
+	$(ASYNCIFY) hello_prompt_asyncfiy.pre.wasm -o hello_prompt_asyncify.wasm
+	chmod +x hello_prompt_asyncify.wasm
+
+hello_forward_prompt_asyncify.wasm: inc/fiber.h src/asyncify/asyncify_prompt_impl.c examples/prompt/hello_forward.c
+	$(WASICC) -DSTACK_POOL_SIZE=$(STACK_POOL_SIZE) -DASYNCIFY_DEFAULT_STACK_SIZE=$(ASYNCIFY_DEFAULT_STACK_SIZE) src/asyncify/asyncify_prompt_impl.c $(WASIFLAGS) examples/prompt/hello_forward.c -o hello_forward_prompt_asyncfiy.pre.wasm
+	$(ASYNCIFY) hello_forward_prompt_asyncfiy.pre.wasm -o hello_forward_prompt_asyncify.wasm
+	chmod +x hello_forward_prompt_asyncify.wasm
+
+
 .PHONY: sieve
 sieve: sieve_asyncify.wasm sieve_wasmfx.wasm
 

examples/hello.c

@@ -30,8 +30,7 @@ void* world(void *arg) {
   return NULL;
 }
 
-int main(void) {
-  fiber_init();
+int prog(int __attribute__((unused)) argc, char** __attribute__((unused)) argv) {
   fiber_result_t status;
   fiber_t hello_fiber = fiber_alloc(hello);
   fiber_t world_fiber = fiber_alloc(world);
@@ -61,6 +60,9 @@ int main(void) {
   fiber_free(hello_fiber);
   fiber_free(world_fiber);
 
-  fiber_finalize();
   return 0;
 }
+
+int main(int argc, char** argv) {
+  return fiber_main(prog, argc, argv);
+}

examples/itersum.c

@@ -6,7 +6,8 @@
 
 
 void* sum(void *arg) {
-  int32_t max = (int32_t)(intptr_t)arg;
+  int32_t max = 0;
+  max = (int32_t)(intptr_t)arg;
   for (int32_t i = 0; i < max; i++) {
     fiber_yield((void*)(intptr_t)i);
   }
@@ -29,19 +30,21 @@ int32_t run(int32_t max) {
   return result;
 }
 
-int main(int argc, char** argv) {
+int prog(int argc, char** argv) {
   if (argc != 2) {
     fprintf(stderr, "Wrong number of arguments. Expected: 1");
     return -1;
   }
-  fiber_init();
 
   int i = atoi(argv[1]);
 
   int32_t result = run(i);
 
   printf("%d\n", result);
 
-  fiber_finalize();
   return 0;
 }
+
+int main(int argc, char** argv) {
+  return (int)fiber_main(prog, argc, argv);
+}

examples/sieve.c

@@ -34,7 +34,7 @@ static void print_input_error_and_exit(void) {
   exit(1);
 }
 
-int main(int argc, char **argv) {
+int prog(int argc, char **argv) {
   if (argc != 2) {
     printf("usage: %s <n>\n", argv[0]);
     exit(1);
@@ -53,7 +53,6 @@ int main(int argc, char **argv) {
   uint32_t p = 0;                         // number of primes computed so far.
   int32_t i = 2;                          // the current candidate prime number.
 
-  fiber_init();
   fiber_t *filters = (fiber_t*)malloc(sizeof(fiber_t) * max_primes);
   fiber_result_t status;
 
@@ -91,7 +90,10 @@ int main(int argc, char **argv) {
     fiber_free(filters[i]);
   }
   free(filters);
-  fiber_finalize();
 
   return 0;
 }
+
+int main(int argc, char** argv) {
+  return fiber_main(prog, argc, argv);
+}

examples/treesum.c

@@ -70,12 +70,11 @@ int32_t run(node_t* tree) {
   return sum;
 }
 
-int main(int argc, char** argv) {
+int prog(int argc, char** argv) {
   if (argc != 2) {
     fprintf(stderr, "Wrong number of arguments. Expected: 1");
     return -1;
   }
-  fiber_init();
 
   int i = atoi(argv[1]);
   node_t *tree = build_tree((int32_t)i, 0);
@@ -86,6 +85,9 @@ int main(int argc, char** argv) {
 
   printf("%d\n", result);
 
-  fiber_finalize();
   return 0;
 }
+
+int main(int argc, char** argv) {
+  return fiber_main(prog, argc, argv);
+}

inc/fiber.h

@@ -35,15 +35,9 @@ export("fiber_resume")
 void* fiber_resume(fiber_t fiber, void *arg, fiber_result_t *status);
 
 
-/** Initialises the fiber runtime. It must be called exactly once
-    before using any of the other fiber_* functions. **/
-export("fiber_init")
-void fiber_init(void);
-
-/** Tears down the fiber runtime. It must be called after the final
-    use of any of the other fiber_* functions. **/
-export("fiber_finalize")
-void fiber_finalize(void);
+/** Runs the provided `main` function in a fiber context. **/
+export("fiber_main")
+int fiber_main(int (*main)(int,char**), int, char**);
 
 #undef export
 #endif

inc/fiber/prompt.h

@@ -0,0 +1,57 @@
+/** A basic fiber interface. **/
+#ifdef WASMFX_FIBER_C_H
+#error "the prompt implementation conflicts with the standard implementation"
+#endif
+#ifndef WASMFX_FIBER_C_PROMPT_H
+#define WASMFX_FIBER_C_PROMPT_H
+
+#define export(NAME) __attribute__((export_name(NAME)))
+
+#include <stdint.h>
+
+/** Type of a prompt. **/
+typedef uint32_t prompt_t;
+
+/** The result type of a yield. **/
+typedef struct yield_result {
+  prompt_t prompt;
+  void* value;
+} yield_result_t;
+
+/** The signature of a fiber entry point. **/
+typedef void* (*fiber_entry_point_t)(prompt_t, void*);
+
+/** The abstract type of a fiber object. **/
+typedef struct fiber* fiber_t;
+
+/** Allocates a new fiber with the default stack size. **/
+export("fiber_alloc")
+fiber_t fiber_alloc(fiber_entry_point_t entry);
+
+/** Reclaims the memory occupied by the fiber object. **/
+export("fiber_free")
+void fiber_free(fiber_t fiber);
+
+/** Yields control to the context of the provided prompt. This
+    function must be called from within a fiber context. **/
+export("fiber_yield_to")
+yield_result_t fiber_yield_to(prompt_t p, void *arg);
+
+/** Possible status codes for `fiber_resume`. **/
+typedef enum { FIBER_OK = 0, FIBER_YIELD = 1, FIBER_ERROR = 2, FIBER_FORWARD = 3 } fiber_result_t;
+
+/** Resumes a given `fiber` with argument `arg`, returning some value
+    of type `void*`. The output parameter `status` indicates whether
+    the fiber ran to completion (`FIBER_OK`), yielded control
+    (`FIBER_YIELD`), or failed (`FIBER_ERROR`), in the latter case the
+    return value will always be `NULL`. **/
+export("fiber_resume_with")
+void* fiber_resume_with(fiber_t fiber, void *arg, fiber_result_t *status);
+
+
+/** Runs the provided `main` function in a fiber context. **/
+export("fiber_main")
+int fiber_main(int (*main)(int,char**), int, char**);
+
+#undef export
+#endif

inc/wasi-io.h

@@ -0,0 +1,27 @@
+#ifndef __WASI_IO_H
+#define __WASI_IO_H
+
+#include <stdint.h>
+#include <unistd.h>
+#include <wasi/api.h>
+
+// NOTE: We cannot use printf() and most friends because asyncify
+// attempts to transform them and inadvertently ending up corrupting
+// its own state resulting in an "unreachable" error at runtime.
+// The following code is adapted from
+//   https://gist.github.com/s-macke/6dd78c78be46214d418454abb667a1ba
+#define wasi_print(str) do { \
+    const uint8_t *start = (uint8_t *)str; \
+    const uint8_t *end = start; \
+    for (; *end != '\0'; end++) {} \
+    __wasi_ciovec_t iov = {.buf = start, .buf_len = end - start}; \
+    size_t nwritten; \
+    (void)__wasi_fd_write(STDOUT_FILENO, &iov, 1, &nwritten);   \
+} while (0)
+#define wasi_print_debug(str) \
+    wasi_print(__FILE__ ":" STRINGIZE(__LINE__) ": " str "\n")
+#define wasi_printc(ch) do { \
+    const char str[] = { ch }; \
+    wasi_print(str); \
+} while (0)
+#endif

src/asyncify/asyncify_impl.c

@@ -16,7 +16,7 @@
 // * asyncify_start_rewind(iptr): initiates a continuation
 //   reinstatement. The argument `iptr` is a pointer to an asyncify
 //   stack.
-// * asyncfiy_stop_rewind(): delimits the extent of a continuation
+// * asyncify_stop_rewind(): delimits the extent of a continuation
 //  reinstatement.
 extern
 import("start_unwind")
@@ -226,4 +226,11 @@ void fiber_finalize(void) {
 #endif
 }
 
+int fiber_main(int (*main)(int, char**), int argc, char** argv) {
+  fiber_init();
+  int ans = main(argc, argv);
+  fiber_finalize();
+  return ans;
+}
+
 #undef import