treewide: rework exception handling

Use setjmp() and longjmp() to deal with runtime exceptions.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

5 files changed, 97 insertions, 106 deletions

diff --git a/ast.c b/ast.c
index cb6f438..85825b8 100644
--- a/ast.c
+++ b/ast.c
@@ -262,7 +262,7 @@ ut_reset(struct ut_state *s)
 	s->off = 0;
 
 	if (s->error.code == UT_ERROR_EXCEPTION)
-		json_object_put(s->error.info.exception);
+		free(s->error.info.exception.message);
 
 	memset(&s->error, 0, sizeof(s->error));
 }
diff --git a/ast.h b/ast.h
index 3466beb..cac75d2 100644
--- a/ast.h
+++ b/ast.h
@@ -20,6 +20,7 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <stdbool.h>
+#include <setjmp.h>
 
 #ifdef JSONC
 	#include <json.h>
@@ -86,9 +87,13 @@ struct ut_state {
 	struct {
 		enum ut_error_type code;
 		union {
-			struct json_object *exception;
+			struct {
+				size_t off;
+				char *message;
+			} exception;
 			uint64_t tokens[2];
 		} info;
+		jmp_buf jmp;
 	} error;
 	struct {
 		struct json_object **scope;
diff --git a/eval.c b/eval.c
index dfc599c..954f596 100644
--- a/eval.c
+++ b/eval.c
@@ -25,13 +25,9 @@
 #include <stdlib.h>
 #include <stdarg.h>
 
-char exception_tag_space[sizeof(struct ut_op) + sizeof(struct ut_op *)];
-static struct ut_op *exception_tag = (struct ut_op *)exception_tag_space;
-
-__attribute__((format(printf, 3, 0))) struct json_object *
-ut_exception(struct ut_state *state, uint32_t off, const char *fmt, ...)
+__attribute__((noreturn,format(printf, 3, 0))) void
+ut_throw(struct ut_state *state, uint32_t off, const char *fmt, ...)
 {
-	struct json_object *msg;
 	va_list ap;
 	char *s;
 	int len;
@@ -40,23 +36,11 @@ ut_exception(struct ut_state *state, uint32_t off, const char *fmt, ...)
 	len = vasprintf(&s, fmt, ap);
 	va_end(ap);
 
-	if (len < 0) {
-		msg = json_object_new_string(UT_ERRMSG_OOM);
-	}
-	else {
-		msg = json_object_new_string_len(s, len);
-		free(s);
-	}
-
- 	exception_tag->type = T_EXCEPTION;
-	exception_tag->tree.operand[0] = off;
-
-	json_object_set_userdata(msg, exception_tag, NULL);
-
 	state->error.code = UT_ERROR_EXCEPTION;
-	state->error.info.exception = msg;
+	state->error.info.exception.message = len ? s : NULL;
+	state->error.info.exception.off = off;
 
-	return json_object_get(msg);
+	longjmp(state->error.jmp, 1);
 }
 
 bool
@@ -181,13 +165,13 @@ ut_addscope(struct ut_state *state, uint32_t decl)
 	struct json_object *scope, **tmp;
 
 	if (state->stack.off >= 255)
-		return ut_exception(state, decl, "Runtime error: Too much recursion");
+		ut_throw(state, decl, "Runtime error: Too much recursion");
 
 	if (state->stack.off >= state->stack.size) {
 		tmp = realloc(state->stack.scope, (state->stack.size + 1) * sizeof(*state->stack.scope));
 
 		if (!tmp)
-			return ut_exception(state, decl, UT_ERRMSG_OOM);
+			ut_throw(state, decl, UT_ERRMSG_OOM);
 
 		state->stack.scope = tmp;
 		state->stack.size++;
@@ -196,7 +180,7 @@ ut_addscope(struct ut_state *state, uint32_t decl)
 	scope = ut_new_object(NULL);
 
 	if (!scope)
-		return ut_exception(state, decl, UT_ERRMSG_OOM);
+		ut_throw(state, decl, UT_ERRMSG_OOM);
 
 	state->stack.scope[state->stack.off++] = scope;
 
@@ -344,7 +328,7 @@ ut_getref_required(struct ut_state *state, uint32_t off, struct json_object **ke
 	struct ut_op *op = ut_get_op(state, off);
 	uint32_t off1 = op ? op->tree.operand[0] : 0;
 	struct json_object *scope, *skey, *rv;
-	char *lhs;
+	char *lhs, *p;
 
 	scope = ut_getref(state, off, &skey);
 
@@ -353,17 +337,20 @@ ut_getref_required(struct ut_state *state, uint32_t off, struct json_object **ke
 		lhs = off1 ? ut_ref_to_str(state, off1) : NULL;
 
 		if (lhs) {
-			rv = ut_exception(state, off1, "Type error: %s is null", lhs);
-
+			p = alloca(strlen(lhs) + 1);
+			strcpy(p, lhs);
 			free(lhs);
+
+			json_object_put(scope);
+			ut_throw(state, off1, "Type error: %s is null", p);
 		}
 		else {
-			rv = ut_exception(state, off,
-				"Syntax error: Invalid left-hand side operand %s", tokennames[op->type]);
+			json_object_put(scope);
+			ut_throw(state, off,
+			         "Syntax error: Invalid left-hand side operand %s",
+			         tokennames[op->type]);
 		}
 
-		json_object_put(scope);
-
 		*key = NULL;
 		return rv;
 	}
@@ -543,14 +530,14 @@ ut_execute_for(struct ut_state *state, uint32_t off)
 		}
 
 		if (init->type != T_IN)
-			return ut_exception(state, ut_get_off(state, init),
-			                    "Syntax error: missing ';' after for loop initializer");
+			ut_throw(state, ut_get_off(state, init),
+			         "Syntax error: missing ';' after for loop initializer");
 
 		ivar = ut_get_op(state, init->tree.operand[0]);
 
 		if (!ivar || ivar->type != T_LABEL)
-			return ut_exception(state, ut_get_off(state, init),
-			                    "Syntax error: invalid for-in left-hand side");
+			ut_throw(state, ut_get_off(state, init),
+			         "Syntax error: invalid for-in left-hand side");
 
 		val = ut_execute_op(state, init->tree.operand[1]);
 		scope = local ? ut_getscope(state, 0) : ut_getref(state, ut_get_off(state, ivar), NULL);
@@ -914,7 +901,7 @@ ut_execute_list(struct ut_state *state, uint32_t off)
 	struct json_object *arr = json_object_new_array();
 
 	if (!arr)
-		return ut_exception(state, off, UT_ERRMSG_OOM);
+		ut_throw(state, off, UT_ERRMSG_OOM);
 
 	while (op) {
 		json_object_array_add(arr, ut_execute_op(state, ut_get_off(state, op)));
@@ -931,7 +918,7 @@ ut_execute_object(struct ut_state *state, uint32_t off)
 	struct ut_op *key, *val;
 
 	if (!obj)
-		return ut_exception(state, off, UT_ERRMSG_OOM);
+		ut_throw(state, off, UT_ERRMSG_OOM);
 
 	for (key = ut_get_child(state, off, 0), val = ut_get_op(state, key ? key->tree.next : 0);
 	     key != NULL && val != NULL;
@@ -985,9 +972,9 @@ ut_invoke(struct ut_state *state, uint32_t off, struct json_object *scope,
 	case T_BREAK:
 	case T_CONTINUE:
 		ut_putval(rv);
-		rv = ut_exception(state, ut_get_off(state, tag),
-		                  "Syntax error: %s statement must be inside loop",
-		                  tokennames[tag->type]);
+		ut_throw(state, ut_get_off(state, tag),
+		         "Syntax error: %s statement must be inside loop",
+		         tokennames[tag->type]);
 		break;
 
 	case T_RETURN:
@@ -1025,15 +1012,21 @@ ut_execute_call(struct ut_state *state, uint32_t off)
 	struct ut_op *decl = func ? json_object_get_userdata(func) : NULL;
 	struct json_object *argvals = ut_execute_list(state, off2);
 	struct json_object *rv;
-	char *lhs;
+	char *lhs, *p;
 
 	if (!decl || (decl->type != T_FUNC && decl->type != T_CFUNC)) {
 		lhs = ut_ref_to_str(state, off1);
-		rv = ut_exception(state, off1,
-			"Type error: %s is not a function",
-			lhs ? lhs : "left-hand side expression");
 
-		free(lhs);
+		if (lhs) {
+			p = alloca(strlen(lhs) + 1);
+			strcpy(p, lhs);
+			free(lhs);
+		}
+		else {
+			p = "left-hand side expression";
+		}
+
+		ut_throw(state, off1, "Type error: %s is not a function", p);
 	}
 	else {
 		rv = ut_invoke(state, off, NULL, func, argvals);
@@ -1309,7 +1302,7 @@ ut_execute_function(struct ut_state *state, uint32_t off)
 	struct json_object *obj = ut_new_func(op);
 
 	if (!obj)
-		return ut_exception(state, off, UT_ERRMSG_OOM);
+		ut_throw(state, off, UT_ERRMSG_OOM);
 
 	return obj;
 }
@@ -1471,7 +1464,7 @@ ut_execute_op(struct ut_state *state, uint32_t off)
 		return ut_execute_break_cont(state, off);
 
 	default:
-		return ut_exception(state, off, "Runtime error: Unrecognized opcode %d", op->type);
+		ut_throw(state, off, "Runtime error: Unrecognized opcode %d", op->type);
 	}
 }
 
@@ -1529,32 +1522,24 @@ ut_globals_init(struct ut_state *state, struct json_object *scope)
 enum ut_error_type
 ut_run(struct ut_state *state)
 {
+	struct json_object *entry = NULL, *scope = NULL, *args = NULL, *rv = NULL;
 	struct ut_op *op = ut_get_op(state, state->main);
-	struct json_object *entry, *scope, *args, *rv;
 
-	if (!op || op->type != T_FUNC) {
-		ut_exception(state, state->main, "Runtime error: Invalid root operation in AST");
+	if (!setjmp(state->error.jmp)) {
+		if (!op || op->type != T_FUNC)
+			ut_throw(state, state->main, "Runtime error: Invalid root operation in AST");
 
-		return UT_ERROR_EXCEPTION;
-	}
+		entry = ut_execute_function(state, state->main);
+		scope = ut_addscope(state, state->main);
 
-	entry = ut_execute_function(state, state->main);
-
-	if (!entry)
-		return UT_ERROR_EXCEPTION;
-
-	scope = ut_addscope(state, state->main);
-
-	if (!json_object_is_type(scope, json_type_object))
-		return UT_ERROR_EXCEPTION;
-
-	state->ctx = NULL;
+		state->ctx = NULL;
 
-	ut_globals_init(state, scope);
-	ut_lib_init(state, scope);
+		ut_globals_init(state, scope);
+		ut_lib_init(state, scope);
 
-	args = json_object_new_array();
-	rv = ut_invoke(state, state->main, NULL, entry, args);
+		args = json_object_new_array();
+		rv = ut_invoke(state, state->main, NULL, entry, args);
+	}
 
 	json_object_put(entry);
 	json_object_put(args);
diff --git a/eval.h b/eval.h
index 7f707ca..30d29d5 100644
--- a/eval.h
+++ b/eval.h
@@ -24,8 +24,8 @@
 
 #include "ast.h"
 
-__attribute__((format(printf, 3, 0))) struct json_object *
-ut_exception(struct ut_state *state, uint32_t op, const char *fmt, ...);
+__attribute__((noreturn,format(printf, 3, 0))) void
+ut_throw(struct ut_state *state, uint32_t off, const char *fmt, ...);
 
 void
 ut_putval(struct json_object *val);
diff --git a/lib.c b/lib.c
index 1ca1c6d..d2222f4 100644
--- a/lib.c
+++ b/lib.c
@@ -134,10 +134,10 @@ char *
 ut_format_error(struct ut_state *state, const char *expr)
 {
 	size_t off = state ? state->off : 0;
-	struct ut_op *tag;
-	bool first = true;
+	char *msg = NULL, *p;
 	size_t msglen = 0;
-	char *msg = NULL;
+	bool first = true;
+	struct ut_op *op;
 	int i, max_i;
 
 	switch (state ? state->error.code : UT_ERROR_OUT_OF_MEMORY) {
@@ -202,10 +202,11 @@ ut_format_error(struct ut_state *state, const char *expr)
 		break;
 
 	case UT_ERROR_EXCEPTION:
-		tag = json_object_get_userdata(state->error.info.exception);
-		off = (tag && tag->tree.operand[0]) ? ut_get_op(state, tag->tree.operand[0])->off : 0;
+		p = state->error.info.exception.message;
+		op = ut_get_op(state, state->error.info.exception.off);
+		off = op ? op->off : 0;
 
-		sprintf_append(&msg, &msglen, "%s\n", json_object_get_string(state->error.info.exception));
+		sprintf_append(&msg, &msglen, "%s\n", p ? p : UT_ERRMSG_OOM);
 		break;
 	}
 
@@ -509,7 +510,7 @@ ut_chr(struct ut_state *s, uint32_t off, struct json_object *args)
 	str = calloc(1, len);
 
 	if (!str)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	for (idx = 0; idx < len; idx++) {
 		n = ut_cast_int64(json_object_array_get_idx(args, idx));
@@ -553,7 +554,7 @@ ut_die(struct ut_state *s, uint32_t off, struct json_object *args)
 {
 	const char *msg = json_object_get_string(json_object_array_get_idx(args, 0));
 
-	return ut_exception(s, off, "%s", msg ? msg : "Died");
+	ut_throw(s, off, "%s", msg ? msg : "Died");
 }
 
 static struct json_object *
@@ -603,7 +604,7 @@ ut_filter(struct ut_state *s, uint32_t off, struct json_object *args)
 		ut_putval(arr);
 		ut_putval(cmpargs);
 
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 	}
 
 	json_object_array_put_idx(cmpargs, 2, json_object_get(obj));
@@ -679,7 +680,7 @@ ut_join(struct ut_state *s, uint32_t off, struct json_object *args)
 	p = res = calloc(1, len);
 
 	if (!res)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	for (arrlen = json_object_array_length(arr), arridx = 0; arridx < arrlen; arridx++) {
 		if (arridx > 0) {
@@ -725,7 +726,7 @@ ut_keys(struct ut_state *s, uint32_t off, struct json_object *args)
 	arr = json_object_new_array();
 
 	if (!arr)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	json_object_object_foreach(obj, key, val)
 		json_object_array_add(arr, json_object_new_string(key));
@@ -747,7 +748,7 @@ ut_lc(struct ut_state *s, uint32_t off, struct json_object *args)
 	res = p = calloc(1, len);
 
 	if (!res)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	while (*str)
 		if (*str >= 'A' && *str <= 'Z')
@@ -779,7 +780,7 @@ ut_map(struct ut_state *s, uint32_t off, struct json_object *args)
 		ut_putval(arr);
 		ut_putval(cmpargs);
 
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 	}
 
 	json_object_array_put_idx(cmpargs, 2, json_object_get(obj));
@@ -865,7 +866,7 @@ ut_reverse(struct ut_state *s, uint32_t off, struct json_object *args)
 		rv = json_object_new_array();
 
 		if (!rv)
-			return ut_exception(s, off, UT_ERRMSG_OOM);
+			ut_throw(s, off, UT_ERRMSG_OOM);
 
 		for (arridx = json_object_array_length(obj); arridx > 0; arridx--)
 			json_object_array_add(rv, json_object_get(json_object_array_get_idx(obj, arridx - 1)));
@@ -876,7 +877,7 @@ ut_reverse(struct ut_state *s, uint32_t off, struct json_object *args)
 		p = dup = calloc(1, len + 1);
 
 		if (!dup)
-			return ut_exception(s, off, UT_ERRMSG_OOM);
+			ut_throw(s, off, UT_ERRMSG_OOM);
 
 		while (len > 0)
 			*p++ = str[--len];
@@ -935,7 +936,7 @@ ut_sort(struct ut_state *s, uint32_t off, struct json_object *args)
 		sort_ctx.args = json_object_new_array();
 
 		if (!sort_ctx.args)
-			return ut_exception(s, off, UT_ERRMSG_OOM);
+			ut_throw(s, off, UT_ERRMSG_OOM);
 	}
 
 	json_object_array_sort(arr, sort_fn);
@@ -1032,7 +1033,7 @@ ut_split(struct ut_state *s, uint32_t off, struct json_object *args)
 	arr = json_object_new_array();
 
 	if (!arr)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	sepstr = json_object_get_string(sep);
 	splitstr = json_object_get_string(str);
@@ -1139,7 +1140,7 @@ ut_uc(struct ut_state *s, uint32_t off, struct json_object *args)
 	res = p = calloc(1, len);
 
 	if (!res)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	while (*str)
 		if (*str >= 'a' && *str <= 'z')
@@ -1180,7 +1181,7 @@ ut_uchr(struct ut_state *s, uint32_t off, struct json_object *args)
 	str = calloc(1, ulen);
 
 	if (!str)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	for (idx = 0, p = str, rem = ulen; idx < len; idx++) {
 		n = ut_cast_int64(json_object_array_get_idx(args, idx));
@@ -1207,7 +1208,7 @@ ut_values(struct ut_state *s, uint32_t off, struct json_object *args)
 	arr = json_object_new_array();
 
 	if (!arr)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	json_object_object_foreach(obj, key, val) {
 		(void)key;
@@ -1470,7 +1471,7 @@ ut_sprintf(struct ut_state *s, uint32_t off, struct json_object *args)
 	len = ut_printf_common(s, off, args, &str);
 
 	if (!str)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	return json_object_new_string_len(str, len);
 }
@@ -1484,7 +1485,7 @@ ut_printf(struct ut_state *s, uint32_t off, struct json_object *args)
 	len = ut_printf_common(s, off, args, &str);
 
 	if (!str)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	len = fwrite(str, 1, len, stdout);
 
@@ -1506,17 +1507,17 @@ ut_require_so(struct ut_state *s, uint32_t off, const char *path)
 	dlh = dlopen(path, RTLD_LAZY|RTLD_LOCAL);
 
 	if (!dlh)
-		return ut_exception(s, off, "Unable to dlopen file %s: %s", path, dlerror());
+		ut_throw(s, off, "Unable to dlopen file %s: %s", path, dlerror());
 
 	init = dlsym(dlh, "ut_module_init");
 
 	if (!init)
-		return ut_exception(s, off, "Module %s provides no 'ut_module_init' function", path);
+		ut_throw(s, off, "Module %s provides no 'ut_module_init' function", path);
 
 	scope = json_object_new_object();
 
 	if (!scope)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	init(&ut, s, scope);
 
@@ -1526,8 +1527,8 @@ ut_require_so(struct ut_state *s, uint32_t off, const char *path)
 static struct json_object *
 ut_require_utpl(struct ut_state *s, uint32_t off, const char *path)
 {
-	struct json_object *ex, *scope;
-	char *source, *msg;
+	struct json_object *scope;
+	char *source, *msg, *p;
 	struct stat st;
 	FILE *sfile;
 
@@ -1537,14 +1538,14 @@ ut_require_utpl(struct ut_state *s, uint32_t off, const char *path)
 	sfile = fopen(path, "rb");
 
 	if (!sfile)
-		return ut_exception(s, off, "Unable to open file %s: %s", path, strerror(errno));
+		ut_throw(s, off, "Unable to open file %s: %s", path, strerror(errno));
 
 	source = calloc(1, st.st_size + 1);
 
 	if (!source) {
 		fclose(sfile);
 
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 	}
 
 	fread(source, 1, st.st_size, sfile);
@@ -1552,12 +1553,12 @@ ut_require_utpl(struct ut_state *s, uint32_t off, const char *path)
 
 	if (ut_parse(s, source)) {
 		msg = ut_format_error(s, source);
-		ex = ut_exception(s, off, "Module loading failed: %s", msg);
-
+		p = alloca(strlen(msg));
+		strcpy(p, msg);
 		free(source);
 		free(msg);
 
-		return ex;
+		ut_throw(s, off, "Module loading failed: %s", p);
 	}
 
 	free(source);
@@ -1565,7 +1566,7 @@ ut_require_utpl(struct ut_state *s, uint32_t off, const char *path)
 	scope = json_object_new_object();
 
 	if (!scope)
-		return ut_exception(s, off, UT_ERRMSG_OOM);
+		ut_throw(s, off, UT_ERRMSG_OOM);
 
 	return ut_invoke(s, off, scope, ut_get_op(s, s->main)->val, NULL);
 }
@@ -1626,7 +1627,7 @@ ut_require(struct ut_state *s, uint32_t off, struct json_object *args)
 	search = json_object_object_get(s->stack.scope[0], "REQUIRE_SEARCH_PATH");
 
 	if (!json_object_is_type(search, json_type_array))
-		return ut_exception(s, off, "Global require search path not set");
+		ut_throw(s, off, "Global require search path not set");
 
 	for (arridx = 0, arrlen = json_object_array_length(search); arridx < arrlen; arridx++) {
 		se = json_object_array_get_idx(search, arridx);
@@ -1640,7 +1641,7 @@ ut_require(struct ut_state *s, uint32_t off, struct json_object *args)
 			return res;
 	}
 
-	return ut_exception(s, off, "No module named '%s' could be found", name);
+	ut_throw(s, off, "No module named '%s' could be found", name);
 }
 
 static struct json_object *