draft of Duktape.act() for enumerating activations, not sure if this is a good idea

src/duk_bi_duktape.c

@@ -154,6 +154,62 @@ duk_ret_t duk_bi_duktape_object_line(duk_context *ctx) {
 }
 #endif  /* DUK_USE_PC2LINE */
 
+duk_ret_t duk_bi_duktape_object_act(duk_context *ctx) {
+	duk_hthread *thr = (duk_hthread *) ctx;
+	duk_activation *act;
+	duk_hobject *h_func;
+	duk_hbuffer_fixed *pc2line;
+	duk_uint_fast32_t pc;
+	duk_uint_fast32_t line;
+	duk_int_t level;
+
+	/* -1             = top callstack entry, callstack[callstack_top - 1]
+	 * -callstack_top = bottom callstack entry, callstack[0]
+	 */
+	level = duk_to_int(ctx, 0);
+	if (level >= 0 || -level > (duk_int_t) thr->callstack_top) {
+		return 0;
+	}
+	DUK_ASSERT(level >= -thr->callstack_top && level <= -1);
+	act = thr->callstack + thr->callstack_top + level;
+
+	duk_push_object(ctx);
+
+	h_func = act->func;
+	DUK_ASSERT(h_func != NULL);
+	duk_push_hobject(ctx, h_func);
+
+	pc = (duk_uint_fast32_t) act->pc;
+	duk_push_int(ctx, (int) pc);  /* FIXME: typing */
+
+	duk_get_prop_stridx(ctx, -2, DUK_STRIDX_INT_PC2LINE);
+	if (duk_is_buffer(ctx, -1)) {
+		pc2line = (duk_hbuffer_fixed *) duk_get_hbuffer(ctx, -1);
+		DUK_ASSERT(!DUK_HBUFFER_HAS_DYNAMIC((duk_hbuffer *) pc2line));
+		pc = (duk_uint_fast32_t) act->pc;
+		line = duk_hobject_pc2line_query(pc2line, (duk_uint_fast32_t) pc);
+	} else {
+		line = 0;
+	}
+	duk_pop(ctx);
+
+	duk_push_int(ctx, (int) line);  /* FIXME: typing */
+
+	/* Providing access to e.g. act->lex_env would be dangerous: these
+	 * internal structures must never be accessible to the application.
+	 * Duktape relies on them having consistent data, and this consistency
+	 * is only asserted for, not checked for.
+	 */
+
+	/* [ level obj func pc line ] */
+
+	/* FIXME: version specific array format instead? */
+	duk_def_prop_stridx(ctx, -4, DUK_STRIDX_LINE_NUMBER, DUK_PROPDESC_FLAGS_WEC);
+	duk_def_prop_stridx(ctx, -3, DUK_STRIDX_PC, DUK_PROPDESC_FLAGS_WEC);
+	duk_def_prop_stridx(ctx, -2, DUK_STRIDX_LC_FUNCTION, DUK_PROPDESC_FLAGS_WEC);
+	return 1;
+}
+
 duk_ret_t duk_bi_duktape_object_gc(duk_context *ctx) {
 #ifdef DUK_USE_MARK_AND_SWEEP
 	duk_hthread *thr = (duk_hthread *) ctx;

src/duk_bi_protos.h

@@ -59,6 +59,7 @@ void duk_bi_date_format_timeval(duk_double_t timeval, duk_uint8_t *out_buf);
 
 duk_ret_t duk_bi_duktape_object_info(duk_context *ctx);
 duk_ret_t duk_bi_duktape_object_line(duk_context *ctx);
+duk_ret_t duk_bi_duktape_object_act(duk_context *ctx);
 duk_ret_t duk_bi_duktape_object_gc(duk_context *ctx);
 duk_ret_t duk_bi_duktape_object_fin(duk_context *ctx);
 duk_ret_t duk_bi_duktape_object_enc(duk_context *ctx);

src/genbuiltins.py

@@ -1098,6 +1098,7 @@ bi_duktape = {
 	'functions': [
 		{ 'name': 'info',			'native': 'duk_bi_duktape_object_info',		'length': 1 },
 		{ 'name': 'line',			'native': 'duk_bi_duktape_object_line',		'length': 0 },
+		{ 'name': 'act',			'native': 'duk_bi_duktape_object_act',		'length': 1 },
 		{ 'name': 'gc',				'native': 'duk_bi_duktape_object_gc',		'length': 1 },
 		{ 'name': 'fin',			'native': 'duk_bi_duktape_object_fin',		'length': 0,	'varargs': True },
 		{ 'name': 'enc',			'native': 'duk_bi_duktape_object_enc',		'length': 0,	'varargs': True },

src/genstrings.py

@@ -558,6 +558,7 @@ duk_string_list = [
 	mkstr("version", custom=True),
 	mkstr("info", custom=True),
 	mkstr("line", custom=True),
+	mkstr("act", custom=True),
 	mkstr("gc", custom=True),
 	mkstr("fin", custom=True),
 	mkstr("enc", custom=True),

website/guide/duktapebuiltins.html

@@ -56,6 +56,7 @@ does not block.</p>
 <tr><td class="propname">dec</td><td>Decode a value (hex, base-64, JSONX, JSONC): <code>Duktape.dec('base64', 'Zm9v')</code>.</td></tr>
 <tr><td class="propname">info</td><td>Get internal information (such as heap address and alloc size) of a value in a version specific format.</td></tr>
 <tr><td class="propname">line</td><td>Get current line number.</td></tr>
+<tr><td class="propname">act</td><td>Get information about callstack entry.</td></tr>
 <tr><td class="propname">gc</td><td>Trigger mark-and-sweep garbage collection.</td></tr>
 <tr><td class="propname">compact</td><td>Compact the memory allocated for a value (object).</td></tr>
 <tr><td class="propname">errcreate</td><td>Callback to modify/replace a created error.</td></tr>