Add Math.cbrt() built-in function

config/header-snippets/platform_fillins.h.in

@@ -265,6 +265,17 @@
 #define DUK_SQRT             sqrt
 #endif
 
+/* The functions below exist only in C99/C++11 or later and need a workaround
+ * for platforms that don't include them.  MSVC isn't detected as C99, but
+ * these functions also exist in MSVC 2013 and later so include a clause for
+ * that too.
+ */
+#if defined(DUK_F_C99) || defined(DUK_F_CPP11) || (defined(_MSC_VER) && (_MSC_VER >= 1800))
+#if !defined(DUK_CBRT)
+#define DUK_CBRT             cbrt
+#endif  /* DUK_CBRT */
+#endif  /* DUK_F_C99 */
+
 /* NetBSD 6.0 x86 (at least) has a few problems with pow() semantics,
  * see test-bug-netbsd-math-pow.js.  Use NetBSD specific workaround.
  * (This might be a wider problem; if so, generalize the define name.)

config/other-defines/platform_functions.yaml

@@ -21,6 +21,7 @@
 - define: DUK_EXP
 - define: DUK_LOG
 - define: DUK_SQRT
+- define: DUK_CBRT
 
 # Memory allocation
 - define: DUK_ANSI_MALLOC

src-input/builtins.yaml

@@ -2277,6 +2277,14 @@ objects:
           magic:
             type: math_twoarg
             funcname: "atan2"  # BI_MATH_ATAN2_IDX
+      - key: "cbrt"
+        value:
+          type: function
+          native: duk_bi_math_object_onearg_shared
+          length: 1
+          magic:
+            type: math_onearg
+            funcname: "cbrt"  # BI_MATH_CBRT_IDX
       - key: "ceil"
         value:
           type: function

src-input/duk_bi_math.c

@@ -90,6 +90,30 @@ DUK_LOCAL double duk__fmax_fixed(double x, double y) {
 	return duk_double_fmax(x, y);
 }
 
+DUK_LOCAL double duk__cbrt_fixed(double x) {
+	/* cbrt() is C99.  To avoid hassling embedders with the need to provide a
+	 * cube root function, we can get by with pow().  The result is not
+	 * identical, but that's OK: ES6 says it's implementation-dependent.
+	 */
+
+	duk_small_int_t c = (duk_small_int_t) DUK_FPCLASSIFY(x);
+
+#if defined(DUK_CBRT)
+	/* cbrt() matches ES6 requirements. */
+	return DUK_CBRT(x);
+#else
+	/* pow() does not, however. */
+	if (c == DUK_FP_NAN || c == DUK_FP_INFINITE || c == DUK_FP_ZERO) {
+		return x;
+	}
+	if (DUK_SIGNBIT(x)) {
+		return -DUK_POW(-x, 1.0 / 3.0);
+	} else {
+		return DUK_POW(x, 1.0 / 3.0);
+	}
+#endif
+}
+
 DUK_LOCAL double duk__round_fixed(double x) {
 	/* Numbers half-way between integers must be rounded towards +Infinity,
 	 * e.g. -3.5 must be rounded to -3 (not -4).  When rounded to zero, zero
@@ -192,7 +216,8 @@ DUK_LOCAL const duk__one_arg_func duk__one_arg_funcs[] = {
 	duk__round_fixed,
 	duk__sin,
 	duk__sqrt,
-	duk__tan
+	duk__tan,
+	duk__cbrt_fixed,
 #else
 	DUK_FABS,
 	DUK_ACOS,
@@ -207,6 +232,7 @@ DUK_LOCAL const duk__one_arg_func duk__one_arg_funcs[] = {
 	DUK_SIN,
 	DUK_SQRT,
 	DUK_TAN
+	duk__cbrt_fixed,
 #endif
 };
 
@@ -249,6 +275,19 @@ DUK_INTERNAL duk_ret_t duk_bi_math_object_twoarg_shared(duk_context *ctx) {
 	return 1;
 }
 
+DUK_INTERNAL duk_ret_t duk_bi_math_object_max(duk_context *ctx) {
+	return duk__math_minmax(ctx, -DUK_DOUBLE_INFINITY, duk__fmax_fixed);
+}
+
+DUK_INTERNAL duk_ret_t duk_bi_math_object_min(duk_context *ctx) {
+	return duk__math_minmax(ctx, DUK_DOUBLE_INFINITY, duk__fmin_fixed);
+}
+
+DUK_INTERNAL duk_ret_t duk_bi_math_object_random(duk_context *ctx) {
+	duk_push_number(ctx, (duk_double_t) DUK_UTIL_GET_RANDOM_DOUBLE((duk_hthread *) ctx));
+	return 1;
+}
+
 #if defined(DUK_USE_ES6)
 DUK_INTERNAL duk_ret_t duk_bi_math_object_hypot(duk_context *ctx) {
 	/*
@@ -315,19 +354,6 @@ DUK_INTERNAL duk_ret_t duk_bi_math_object_hypot(duk_context *ctx) {
 	duk_push_number(ctx, (duk_double_t) DUK_SQRT(sum) * max);
 	return 1;
 }
-#endif
-
-DUK_INTERNAL duk_ret_t duk_bi_math_object_max(duk_context *ctx) {
-	return duk__math_minmax(ctx, -DUK_DOUBLE_INFINITY, duk__fmax_fixed);
-}
-
-DUK_INTERNAL duk_ret_t duk_bi_math_object_min(duk_context *ctx) {
-	return duk__math_minmax(ctx, DUK_DOUBLE_INFINITY, duk__fmin_fixed);
-}
-
-DUK_INTERNAL duk_ret_t duk_bi_math_object_random(duk_context *ctx) {
-	duk_push_number(ctx, (duk_double_t) DUK_UTIL_GET_RANDOM_DOUBLE((duk_hthread *) ctx));
-	return 1;
-}
+#endif  /* DUK_USE_ES6 */
 
 #endif  /* DUK_USE_MATH_BUILTIN */

tools/genbuiltins.py

@@ -1201,7 +1201,8 @@ def load_metadata(opts, rom=False, build_info=None, active_opts=None):
     'round': 9,  # BI_MATH_ROUND_IDX
     'sin': 10,   # BI_MATH_SIN_IDX
     'sqrt': 11,  # BI_MATH_SQRT_IDX
-    'tan': 12    # BI_MATH_TAN_IDX
+    'tan': 12,   # BI_MATH_TAN_IDX
+    'cbrt': 13   # BI_MATH_CBRT_IDX
 }
 math_twoarg_magic = {
     'atan2': 0,  # BI_MATH_ATAN2_IDX

util/check_code_policy.py

@@ -68,6 +68,7 @@ def __init__(self, filename, linenumber, line, reason):
     'exp',
     'log',
     'sqrt',
+    'cbrt',
 
     # memory functions
     'malloc',