refactor(libc): move Lua an DOOM stubs into shared libc modules

src/userland/libc/math_ext.c

@@ -0,0 +1,91 @@
+#include "math.h"
+#include "errno.h"
+
+__attribute__((weak)) double ldexp(double x, int expn) {
+    double v = x;
+    int i;
+    if (expn >= 0) {
+        for (i = 0; i < expn; i++) {
+            v *= 2.0;
+        }
+    } else {
+        for (i = 0; i < -expn; i++) {
+            v *= 0.5;
+        }
+    }
+    return v;
+}
+
+__attribute__((weak)) double frexp(double x, int *expn) {
+    int e = 0;
+    double v = x;
+    if (x == 0.0) {
+        *expn = 0;
+        return 0.0;
+    }
+    while (fabs(v) >= 1.0) {
+        v *= 0.5;
+        e++;
+    }
+    while (fabs(v) > 0.0 && fabs(v) < 0.5) {
+        v *= 2.0;
+        e--;
+    }
+    *expn = e;
+    return v;
+}
+
+static double _b_atan_series(double x) {
+    double x2 = x * x;
+    double term = x;
+    double sum = x;
+    int n;
+    for (n = 3; n <= 23; n += 2) {
+        term *= -x2;
+        sum += term / (double)n;
+    }
+    return sum;
+}
+
+static double _b_atan_precise(double x) {
+    if (x < 0.0) {
+        return -_b_atan_precise(-x);
+    }
+    if (x > 1.0) {
+        return (M_PI / 2.0) - _b_atan_precise(1.0 / x);
+    }
+    if (x > 0.5) {
+        double y = (x - 1.0) / (x + 1.0);
+        return (M_PI / 4.0) + _b_atan_series(y);
+    }
+    return _b_atan_series(x);
+}
+
+__attribute__((weak)) double atan2(double y, double x) {
+    if (x > 0.0) {
+        return _b_atan_precise(y / x);
+    }
+    if (x < 0.0) {
+        if (y >= 0.0) return _b_atan_precise(y / x) + M_PI;
+        return _b_atan_precise(y / x) - M_PI;
+    }
+    if (y > 0.0) return M_PI / 2.0;
+    if (y < 0.0) return -M_PI / 2.0;
+    return 0.0;
+}
+
+__attribute__((weak)) double asin(double x) {
+    if (x > 1.0 || x < -1.0) {
+        errno = EDOM;
+        return 0.0;
+    }
+    return atan2(x, sqrt(1.0 - x * x));
+}
+
+__attribute__((weak)) double acos(double x) {
+    if (x > 1.0 || x < -1.0) {
+        errno = EDOM;
+        return 0.0;
+    }
+    return M_PI / 2.0 - asin(x);
+}