Migrate to using musl libc sprintf family to gain compiled asm.js performance. Keep a copy of handwritten vfprintf and fprintf around to be compatible with the Emscripten filesystem IO library. Also migrate frexp which sprintf depends on to musl libc.

14 files changed, 935 insertions, 40 deletions

diff --git a/src/library.js b/src/library.js
index 543b0ff0..24eef829 100644
--- a/src/library.js
+++ b/src/library.js
@@ -2838,16 +2838,6 @@ LibraryManager.library = {
     var stdout = {{{ makeGetValue(makeGlobalUse('_stdout'), '0', 'void*') }}};
     return _fprintf(stdout, format, varargs);
   },
-  sprintf__deps: ['snprintf'],
-  sprintf: function(s, format, varargs) {
-    // int sprintf(char *restrict s, const char *restrict format, ...);
-    // http://pubs.opengroup.org/onlinepubs/000095399/functions/printf.html
-    return _snprintf(s, undefined, format, varargs);
-  },
-  asprintf__deps: ['sprintf'],
-  asprintf: function(s, format, varargs) {
-    return _sprintf(-s, format, varargs);
-  },
   dprintf__deps: ['_formatString', 'write'],
   dprintf: function(fd, format, varargs) {
     var result = __formatString(format, varargs);
@@ -2875,22 +2865,10 @@ LibraryManager.library = {
   vfprintf: function(s, f, va_arg) {
     return _fprintf(s, f, {{{ makeGetValue('va_arg', 0, '*') }}});
   },
-  vsnprintf__deps: ['snprintf'],
-  vsnprintf: function(s, n, format, va_arg) {
-    return _snprintf(s, n, format, {{{ makeGetValue('va_arg', 0, '*') }}});
-  },
   vprintf__deps: ['printf'],
   vprintf: function(format, va_arg) {
     return _printf(format, {{{ makeGetValue('va_arg', 0, '*') }}});
   },
-  vsprintf__deps: ['sprintf'],
-  vsprintf: function(s, format, va_arg) {
-    return _sprintf(s, format, {{{ makeGetValue('va_arg', 0, '*') }}});
-  },
-  vasprintf__deps: ['asprintf'],
-  vasprintf: function(s, format, va_arg) {
-    return _asprintf(s, format, {{{ makeGetValue('va_arg', 0, '*') }}});
-  },
   vdprintf__deps: ['dprintf'],
   vdprintf: function (fd, format, va_arg) {
     return _dprintf(fd, format, {{{ makeGetValue('va_arg', 0, '*') }}});
@@ -4500,23 +4478,6 @@ LibraryManager.library = {
     {{{ makeSetValue('intpart', 0, 'Math.floor(x)', 'float') }}};
     return x - {{{ makeGetValue('intpart', 0, 'float') }}};
   },
-  frexp: function(x, exp_addr) {
-    var sig = 0, exp_ = 0;
-    if (x !== 0) {
-      var sign = 1;
-      if (x < 0) {
-        x = -x;
-        sign = -1;
-      }
-      var raw_exp = Math.log(x)/Math.log(2);
-      exp_ = Math.ceil(raw_exp);
-      if (exp_ === raw_exp) exp_ += 1;
-      sig = sign*x/Math.pow(2, exp_);
-    }
-    {{{ makeSetValue('exp_addr', 0, 'exp_', 'i32') }}};
-    return sig;
-  },
-  frexpf: 'frexp',
   finite: function(x) {
     return isFinite(x);
   },
diff --git a/system/lib/libc/musl/src/internal/stdio_impl.h b/system/lib/libc/musl/src/internal/stdio_impl.h
index 45110df5..0e10e30d 100644
--- a/system/lib/libc/musl/src/internal/stdio_impl.h
+++ b/system/lib/libc/musl/src/internal/stdio_impl.h
@@ -95,7 +95,8 @@ int __fmodeflags(const char *);
 FILE *__fopen_rb_ca(const char *, FILE *, unsigned char *, size_t);
 int __fclose_ca(FILE *);
 
-// XXX Emscripten
+// XXX Emscripten: musl-specific vfscanf and vfprintf live parallel to JS handwritten vfscanf and vfprintf, so musl ones are prefixed.
 int MUSL_vfscanf(FILE *restrict f, const char *restrict fmt, va_list ap);
+int MUSL_vfprintf(FILE *restrict f, const char *restrict fmt, va_list ap);
 
 #endif
diff --git a/system/lib/libc/musl/src/math/frexp.c b/system/lib/libc/musl/src/math/frexp.c
new file mode 100644
index 00000000..27b6266e
--- /dev/null
+++ b/system/lib/libc/musl/src/math/frexp.c
@@ -0,0 +1,23 @@
+#include <math.h>
+#include <stdint.h>
+
+double frexp(double x, int *e)
+{
+	union { double d; uint64_t i; } y = { x };
+	int ee = y.i>>52 & 0x7ff;
+
+	if (!ee) {
+		if (x) {
+			x = frexp(x*0x1p64, e);
+			*e -= 64;
+		} else *e = 0;
+		return x;
+	} else if (ee == 0x7ff) {
+		return x;
+	}
+
+	*e = ee - 0x3fe;
+	y.i &= 0x800fffffffffffffull;
+	y.i |= 0x3fe0000000000000ull;
+	return y.d;
+}
diff --git a/system/lib/libc/musl/src/math/frexpf.c b/system/lib/libc/musl/src/math/frexpf.c
new file mode 100644
index 00000000..07870975
--- /dev/null
+++ b/system/lib/libc/musl/src/math/frexpf.c
@@ -0,0 +1,23 @@
+#include <math.h>
+#include <stdint.h>
+
+float frexpf(float x, int *e)
+{
+	union { float f; uint32_t i; } y = { x };
+	int ee = y.i>>23 & 0xff;
+
+	if (!ee) {
+		if (x) {
+			x = frexpf(x*0x1p64, e);
+			*e -= 64;
+		} else *e = 0;
+		return x;
+	} else if (ee == 0xff) {
+		return x;
+	}
+
+	*e = ee - 0x7e;
+	y.i &= 0x807ffffful;
+	y.i |= 0x3f000000ul;
+	return y.f;
+}
diff --git a/system/lib/libc/musl/src/math/frexpl.c b/system/lib/libc/musl/src/math/frexpl.c
new file mode 100644
index 00000000..f9d90a6d
--- /dev/null
+++ b/system/lib/libc/musl/src/math/frexpl.c
@@ -0,0 +1,37 @@
+#include <math.h>
+#include <stdint.h>
+#include <float.h>
+
+#if LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
+
+/* This version is for 80-bit little endian long double */
+
+long double frexpl(long double x, int *e)
+{
+	union { long double ld; uint16_t hw[5]; } y = { x };
+	int ee = y.hw[4]&0x7fff;
+
+	if (!ee) {
+		if (x) {
+			x = frexpl(x*0x1p64, e);
+			*e -= 64;
+		} else *e = 0;
+		return x;
+	} else if (ee == 0x7fff) {
+		return x;
+	}
+
+	*e = ee - 0x3ffe;
+	y.hw[4] &= 0x8000;
+	y.hw[4] |= 0x3ffe;
+	return y.ld;
+}
+
+#else
+
+long double frexpl(long double x, int *e)
+{
+	return frexp(x, e);
+}
+
+#endif
diff --git a/system/lib/libc/musl/src/stdio/asprintf.c b/system/lib/libc/musl/src/stdio/asprintf.c
new file mode 100644
index 00000000..4ec83534
--- /dev/null
+++ b/system/lib/libc/musl/src/stdio/asprintf.c
@@ -0,0 +1,13 @@
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdarg.h>
+
+int asprintf(char **s, const char *fmt, ...)
+{
+	int ret;
+	va_list ap;
+	va_start(ap, fmt);
+	ret = vasprintf(s, fmt, ap);
+	va_end(ap);
+	return ret;
+}
diff --git a/system/lib/libc/musl/src/stdio/fwrite.c b/system/lib/libc/musl/src/stdio/fwrite.c
new file mode 100644
index 00000000..bf68b794
--- /dev/null
+++ b/system/lib/libc/musl/src/stdio/fwrite.c
@@ -0,0 +1,41 @@
+#include "stdio_impl.h"
+#include <string.h>
+
+size_t __fwritex(const unsigned char *restrict s, size_t l, FILE *restrict f)
+{
+	size_t i=0;
+
+	if (!f->wend && __towrite(f)) return 0;
+
+	if (l > f->wend - f->wpos) return f->write(f, s, l);
+
+	if (f->lbf >= 0) {
+		/* Match /^(.*\n|)/ */
+		for (i=l; i && s[i-1] != '\n'; i--);
+		if (i) {
+			if (f->write(f, s, i) < i)
+				return i;
+			s += i;
+			l -= i;
+		}
+	}
+
+	memcpy(f->wpos, s, l);
+	f->wpos += l;
+	return l+i;
+}
+
+// XXX Emscripten: Not used, since we are not currently using musl file IO.
+#if 0
+size_t fwrite(const void *restrict src, size_t size, size_t nmemb, FILE *restrict f)
+{
+	size_t k, l = size*nmemb;
+	if (!l) return l;
+	FLOCK(f);
+	k = __fwritex(src, l, f);
+	FUNLOCK(f);
+	return k==l ? nmemb : k/size;
+}
+#endif
+
+weak_alias(fwrite, fwrite_unlocked);
diff --git a/system/lib/libc/musl/src/stdio/sprintf.c b/system/lib/libc/musl/src/stdio/sprintf.c
new file mode 100644
index 00000000..9dff524c
--- /dev/null
+++ b/system/lib/libc/musl/src/stdio/sprintf.c
@@ -0,0 +1,12 @@
+#include <stdio.h>
+#include <stdarg.h>
+
+int sprintf(char *restrict s, const char *restrict fmt, ...)
+{
+	int ret;
+	va_list ap;
+	va_start(ap, fmt);
+	ret = vsprintf(s, fmt, ap);
+	va_end(ap);
+	return ret;
+}
diff --git a/system/lib/libc/musl/src/stdio/vasprintf.c b/system/lib/libc/musl/src/stdio/vasprintf.c
new file mode 100644
index 00000000..68b7246b
--- /dev/null
+++ b/system/lib/libc/musl/src/stdio/vasprintf.c
@@ -0,0 +1,28 @@
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+
+#define GUESS 240U
+
+int vasprintf(char **s, const char *fmt, va_list ap)
+{
+	va_list ap2;
+	char *a;
+	int l=GUESS;
+
+	if (!(a=malloc(GUESS))) return -1;
+
+	va_copy(ap2, ap);
+	l=vsnprintf(a, GUESS, fmt, ap2);
+	va_end(ap2);
+
+	if (l<GUESS) {
+		char *b = realloc(a, l+1U);
+		*s = b ? b : a;
+		return l;
+	}
+	free(a);
+	if (l<0 || !(*s=malloc(l+1U))) return -1;
+	return vsnprintf(*s, l+1U, fmt, ap);
+}
diff --git a/system/lib/libc/musl/src/stdio/vfprintf.c b/system/lib/libc/musl/src/stdio/vfprintf.c
new file mode 100644
index 00000000..750ad1e3
--- /dev/null
+++ b/system/lib/libc/musl/src/stdio/vfprintf.c
@@ -0,0 +1,685 @@
+#include "stdio_impl.h"
+#include <errno.h>
+#include <ctype.h>
+#include <limits.h>
+#include <string.h>
+#include <stdarg.h>
+#include <wchar.h>
+#include <inttypes.h>
+#include <math.h>
+#include <float.h>
+
+/* Some useful macros */
+
+#define MAX(a,b) ((a)>(b) ? (a) : (b))
+#define MIN(a,b) ((a)<(b) ? (a) : (b))
+#define CONCAT2(x,y) x ## y
+#define CONCAT(x,y) CONCAT2(x,y)
+
+/* Convenient bit representation for modifier flags, which all fall
+ * within 31 codepoints of the space character. */
+
+#define ALT_FORM   (1U<<'#'-' ')
+#define ZERO_PAD   (1U<<'0'-' ')
+#define LEFT_ADJ   (1U<<'-'-' ')
+#define PAD_POS    (1U<<' '-' ')
+#define MARK_POS   (1U<<'+'-' ')
+#define GROUPED    (1U<<'\''-' ')
+
+#define FLAGMASK (ALT_FORM|ZERO_PAD|LEFT_ADJ|PAD_POS|MARK_POS|GROUPED)
+
+#if UINT_MAX == ULONG_MAX
+#define LONG_IS_INT
+#endif
+
+#if SIZE_MAX != ULONG_MAX || UINTMAX_MAX != ULLONG_MAX
+#define ODD_TYPES
+#endif
+
+/* State machine to accept length modifiers + conversion specifiers.
+ * Result is 0 on failure, or an argument type to pop on success. */
+
+enum {
+	BARE, LPRE, LLPRE, HPRE, HHPRE, BIGLPRE,
+	ZTPRE, JPRE,
+	STOP,
+	PTR, INT, UINT, ULLONG,
+#ifndef LONG_IS_INT
+	LONG, ULONG,
+#else
+#define LONG INT
+#define ULONG UINT
+#endif
+	SHORT, USHORT, CHAR, UCHAR,
+#ifdef ODD_TYPES
+	LLONG, SIZET, IMAX, UMAX, PDIFF, UIPTR,
+#else
+#define LLONG ULLONG
+#define SIZET ULONG
+#define IMAX LLONG
+#define UMAX ULLONG
+#define PDIFF LONG
+#define UIPTR ULONG
+#endif
+	DBL, LDBL,
+	NOARG,
+	MAXSTATE
+};
+
+#define S(x) [(x)-'A']
+
+static const unsigned char states[]['z'-'A'+1] = {
+	{ /* 0: bare types */
+		S('d') = INT, S('i') = INT,
+		S('o') = UINT, S('u') = UINT, S('x') = UINT, S('X') = UINT,
+		S('e') = DBL, S('f') = DBL, S('g') = DBL, S('a') = DBL,
+		S('E') = DBL, S('F') = DBL, S('G') = DBL, S('A') = DBL,
+		S('c') = CHAR, S('C') = INT,
+		S('s') = PTR, S('S') = PTR, S('p') = UIPTR, S('n') = PTR,
+		S('m') = NOARG,
+		S('l') = LPRE, S('h') = HPRE, S('L') = BIGLPRE,
+		S('z') = ZTPRE, S('j') = JPRE, S('t') = ZTPRE,
+	}, { /* 1: l-prefixed */
+		S('d') = LONG, S('i') = LONG,
+		S('o') = ULONG, S('u') = ULONG, S('x') = ULONG, S('X') = ULONG,
+		S('e') = DBL, S('f') = DBL, S('g') = DBL, S('a') = DBL,
+		S('E') = DBL, S('F') = DBL, S('G') = DBL, S('A') = DBL,
+		S('c') = INT, S('s') = PTR, S('n') = PTR,
+		S('l') = LLPRE,
+	}, { /* 2: ll-prefixed */
+		S('d') = LLONG, S('i') = LLONG,
+		S('o') = ULLONG, S('u') = ULLONG,
+		S('x') = ULLONG, S('X') = ULLONG,
+		S('n') = PTR,
+	}, { /* 3: h-prefixed */
+		S('d') = SHORT, S('i') = SHORT,
+		S('o') = USHORT, S('u') = USHORT,
+		S('x') = USHORT, S('X') = USHORT,
+		S('n') = PTR,
+		S('h') = HHPRE,
+	}, { /* 4: hh-prefixed */
+		S('d') = CHAR, S('i') = CHAR,
+		S('o') = UCHAR, S('u') = UCHAR,
+		S('x') = UCHAR, S('X') = UCHAR,
+		S('n') = PTR,
+	}, { /* 5: L-prefixed */
+		S('e') = LDBL, S('f') = LDBL, S('g') = LDBL, S('a') = LDBL,
+		S('E') = LDBL, S('F') = LDBL, S('G') = LDBL, S('A') = LDBL,
+		S('n') = PTR,
+	}, { /* 6: z- or t-prefixed (assumed to be same size) */
+		S('d') = PDIFF, S('i') = PDIFF,
+		S('o') = SIZET, S('u') = SIZET,
+		S('x') = SIZET, S('X') = SIZET,
+		S('n') = PTR,
+	}, { /* 7: j-prefixed */
+		S('d') = IMAX, S('i') = IMAX,
+		S('o') = UMAX, S('u') = UMAX,
+		S('x') = UMAX, S('X') = UMAX,
+		S('n') = PTR,
+	}
+};
+
+#define OOB(x) ((unsigned)(x)-'A' > 'z'-'A')
+
+union arg
+{
+	uintmax_t i;
+	long double f;
+	void *p;
+};
+
+static void pop_arg(union arg *arg, int type, va_list *ap)
+{
+	/* Give the compiler a hint for optimizing the switch. */
+	if ((unsigned)type > MAXSTATE) return;
+	switch (type) {
+	       case PTR:	arg->p = va_arg(*ap, void *);
+	break; case INT:	arg->i = va_arg(*ap, int);
+	break; case UINT:	arg->i = va_arg(*ap, unsigned int);
+#ifndef LONG_IS_INT
+	break; case LONG:	arg->i = va_arg(*ap, long);
+	break; case ULONG:	arg->i = va_arg(*ap, unsigned long);
+#endif
+	break; case ULLONG:	arg->i = va_arg(*ap, unsigned long long);
+	break; case SHORT:	arg->i = (short)va_arg(*ap, int);
+	break; case USHORT:	arg->i = (unsigned short)va_arg(*ap, int);
+	break; case CHAR:	arg->i = (signed char)va_arg(*ap, int);
+	break; case UCHAR:	arg->i = (unsigned char)va_arg(*ap, int);
+#ifdef ODD_TYPES
+	break; case LLONG:	arg->i = va_arg(*ap, long long);
+	break; case SIZET:	arg->i = va_arg(*ap, size_t);
+	break; case IMAX:	arg->i = va_arg(*ap, intmax_t);
+	break; case UMAX:	arg->i = va_arg(*ap, uintmax_t);
+	break; case PDIFF:	arg->i = va_arg(*ap, ptrdiff_t);
+	break; case UIPTR:	arg->i = (uintptr_t)va_arg(*ap, void *);
+#endif
+	break; case DBL:	arg->f = va_arg(*ap, double);
+	break; case LDBL:	arg->f = va_arg(*ap, long double);
+	}
+}
+
+static void out(FILE *f, const char *s, size_t l)
+{
+	__fwritex((void *)s, l, f);
+}
+
+static void pad(FILE *f, char c, int w, int l, int fl)
+{
+	char pad[256];
+	if (fl & (LEFT_ADJ | ZERO_PAD) || l >= w) return;
+	l = w - l;
+	memset(pad, c, l>sizeof pad ? sizeof pad : l);
+	for (; l >= sizeof pad; l -= sizeof pad)
+		out(f, pad, sizeof pad);
+	out(f, pad, l);
+}
+
+static const char xdigits[16] = {
+	"0123456789ABCDEF"
+};
+
+static char *fmt_x(uintmax_t x, char *s, int lower)
+{
+	for (; x; x>>=4) *--s = xdigits[(x&15)]|lower;
+	return s;
+}
+
+static char *fmt_o(uintmax_t x, char *s)
+{
+	for (; x; x>>=3) *--s = '0' + (x&7);
+	return s;
+}
+
+static char *fmt_u(uintmax_t x, char *s)
+{
+	unsigned long y;
+	for (   ; x>ULONG_MAX; x/=10) *--s = '0' + x%10;
+	for (y=x;           y; y/=10) *--s = '0' + y%10;
+	return s;
+}
+
+/* Do not override this check. The floating point printing code below
+ * depends on the float.h constants being right. If they are wrong, it
+ * may overflow the stack. */
+#if LDBL_MANT_DIG == 53
+typedef char compiler_defines_long_double_incorrectly[9-(int)sizeof(long double)];
+#endif
+
+static int fmt_fp(FILE *f, long double y, int w, int p, int fl, int t)
+{
+	uint32_t big[(LDBL_MAX_EXP+LDBL_MANT_DIG)/9+1];
+	uint32_t *a, *d, *r, *z;
+	int e2=0, e, i, j, l;
+	char buf[9+LDBL_MANT_DIG/4], *s;
+	const char *prefix="-0X+0X 0X-0x+0x 0x";
+	int pl;
+	char ebuf0[3*sizeof(int)], *ebuf=&ebuf0[3*sizeof(int)], *estr;
+
+	pl=1;
+	if (signbit(y)) {
+		y=-y;
+	} else if (fl & MARK_POS) {
+		prefix+=3;
+	} else if (fl & PAD_POS) {
+		prefix+=6;
+	} else prefix++, pl=0;
+
+	if (!isfinite(y)) {
+		char *s = (t&32)?"inf":"INF";
+		if (y!=y) s=(t&32)?"nan":"NAN", pl=0;
+		pad(f, ' ', w, 3+pl, fl&~ZERO_PAD);
+		out(f, prefix, pl);
+		out(f, s, 3);
+		pad(f, ' ', w, 3+pl, fl^LEFT_ADJ);
+		return MAX(w, 3+pl);
+	}
+
+	y = frexpl(y, &e2) * 2;
+	if (y) e2--;
+
+	if ((t|32)=='a') {
+		long double round = 8.0;
+		int re;
+
+		if (t&32) prefix += 9;
+		pl += 2;
+
+		if (p<0 || p>=LDBL_MANT_DIG/4-1) re=0;
+		else re=LDBL_MANT_DIG/4-1-p;
+
+		if (re) {
+			while (re--) round*=16;
+			if (*prefix=='-') {
+				y=-y;
+				y-=round;
+				y+=round;
+				y=-y;
+			} else {
+				y+=round;
+				y-=round;
+			}
+		}
+
+		estr=fmt_u(e2<0 ? -e2 : e2, ebuf);
+		if (estr==ebuf) *--estr='0';
+		*--estr = (e2<0 ? '-' : '+');
+		*--estr = t+('p'-'a');
+
+		s=buf;
+		do {
+			int x=y;
+			*s++=xdigits[x]|(t&32);
+			y=16*(y-x);
+			if (s-buf==1 && (y||p>0||(fl&ALT_FORM))) *s++='.';
+		} while (y);
+
+		if (p && s-buf-2 < p)
+			l = (p+2) + (ebuf-estr);
+		else
+			l = (s-buf) + (ebuf-estr);
+
+		pad(f, ' ', w, pl+l, fl);
+		out(f, prefix, pl);
+		pad(f, '0', w, pl+l, fl^ZERO_PAD);
+		out(f, buf, s-buf);
+		pad(f, '0', l-(ebuf-estr)-(s-buf), 0, 0);
+		out(f, estr, ebuf-estr);
+		pad(f, ' ', w, pl+l, fl^LEFT_ADJ);
+		return MAX(w, pl+l);
+	}
+	if (p<0) p=6;
+
+	if (y) y *= 0x1p28, e2-=28;
+
+	if (e2<0) a=r=z=big;
+	else a=r=z=big+sizeof(big)/sizeof(*big) - LDBL_MANT_DIG - 1;
+
+	do {
+		*z = y;
+		y = 1000000000*(y-*z++);
+	} while (y);
+
+	while (e2>0) {
+		uint32_t carry=0;
+		int sh=MIN(29,e2);
+		for (d=z-1; d>=a; d--) {
+			uint64_t x = ((uint64_t)*d<<sh)+carry;
+			*d = x % 1000000000;
+			carry = x / 1000000000;
+		}
+		if (!z[-1] && z>a) z--;
+		if (carry) *--a = carry;
+		e2-=sh;
+	}
+	while (e2<0) {
+		uint32_t carry=0, *b;
+		int sh=MIN(9,-e2);
+		for (d=a; d<z; d++) {
+			uint32_t rm = *d & (1<<sh)-1;
+			*d = (*d>>sh) + carry;
+			carry = (1000000000>>sh) * rm;
+		}
+		if (!*a) a++;
+		if (carry) *z++ = carry;
+		/* Avoid (slow!) computation past requested precision */
+		b = (t|32)=='f' ? r : a;
+		if (z-b > 2+p/9) z = b+2+p/9;
+		e2+=sh;
+	}
+
+	if (a<z) for (i=10, e=9*(r-a); *a>=i; i*=10, e++);
+	else e=0;
+
+	/* Perform rounding: j is precision after the radix (possibly neg) */
+	j = p - ((t|32)!='f')*e - ((t|32)=='g' && p);
+	if (j < 9*(z-r-1)) {
+		uint32_t x;
+		/* We avoid C's broken division of negative numbers */
+		d = r + 1 + ((j+9*LDBL_MAX_EXP)/9 - LDBL_MAX_EXP);
+		j += 9*LDBL_MAX_EXP;
+		j %= 9;
+		for (i=10, j++; j<9; i*=10, j++);
+		x = *d % i;
+		/* Are there any significant digits past j? */
+		if (x || d+1!=z) {
+			long double round = CONCAT(0x1p,LDBL_MANT_DIG);
+			long double small;
+			if (*d/i & 1) round += 2;
+			if (x<i/2) small=0x0.8p0;
+			else if (x==i/2 && d+1==z) small=0x1.0p0;
+			else small=0x1.8p0;
+			if (pl && *prefix=='-') round*=-1, small*=-1;
+			*d -= x;
+			/* Decide whether to round by probing round+small */
+			if (round+small != round) {
+				*d = *d + i;
+				while (*d > 999999999) {
+					*d--=0;
+					(*d)++;
+				}
+				if (d<a) a=d;
+				for (i=10, e=9*(r-a); *a>=i; i*=10, e++);
+			}
+		}
+		if (z>d+1) z=d+1;
+		for (; !z[-1] && z>a; z--);
+	}
+	
+	if ((t|32)=='g') {
+		if (!p) p++;
+		if (p>e && e>=-4) {
+			t--;
+			p-=e+1;
+		} else {
+			t-=2;
+			p--;
+		}
+		if (!(fl&ALT_FORM)) {
+			/* Count trailing zeros in last place */
+			if (z>a && z[-1]) for (i=10, j=0; z[-1]%i==0; i*=10, j++);
+			else j=9;
+			if ((t|32)=='f')
+				p = MIN(p,MAX(0,9*(z-r-1)-j));
+			else
+				p = MIN(p,MAX(0,9*(z-r-1)+e-j));
+		}
+	}
+	l = 1 + p + (p || (fl&ALT_FORM));
+	if ((t|32)=='f') {
+		if (e>0) l+=e;
+	} else {
+		estr=fmt_u(e<0 ? -e : e, ebuf);
+		while(ebuf-estr<2) *--estr='0';
+		*--estr = (e<0 ? '-' : '+');
+		*--estr = t;
+		l += ebuf-estr;
+	}
+
+	pad(f, ' ', w, pl+l, fl);
+	out(f, prefix, pl);
+	pad(f, '0', w, pl+l, fl^ZERO_PAD);
+
+	if ((t|32)=='f') {
+		if (a>r) a=r;
+		for (d=a; d<=r; d++) {
+			char *s = fmt_u(*d, buf+9);
+			if (d!=a) while (s>buf) *--s='0';
+			else if (s==buf+9) *--s='0';
+			out(f, s, buf+9-s);
+		}
+		if (p || (fl&ALT_FORM)) out(f, ".", 1);
+		for (; d<z && p>0; d++, p-=9) {
+			char *s = fmt_u(*d, buf+9);
+			while (s>buf) *--s='0';
+			out(f, s, MIN(9,p));
+		}
+		pad(f, '0', p+9, 9, 0);
+	} else {
+		if (z<=a) z=a+1;
+		for (d=a; d<z && p>=0; d++) {
+			char *s = fmt_u(*d, buf+9);
+			if (s==buf+9) *--s='0';
+			if (d!=a) while (s>buf) *--s='0';
+			else {
+				out(f, s++, 1);
+				if (p>0||(fl&ALT_FORM)) out(f, ".", 1);
+			}
+			out(f, s, MIN(buf+9-s, p));
+			p -= buf+9-s;
+		}
+		pad(f, '0', p+18, 18, 0);
+		out(f, estr, ebuf-estr);
+	}
+
+	pad(f, ' ', w, pl+l, fl^LEFT_ADJ);
+
+	return MAX(w, pl+l);
+}
+
+static int getint(char **s) {
+	int i;
+	for (i=0; isdigit(**s); (*s)++)
+		i = 10*i + (**s-'0');
+	return i;
+}
+
+static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg, int *nl_type)
+{
+	char *a, *z, *s=(char *)fmt;
+	unsigned l10n=0, fl;
+	int w, p;
+	union arg arg;
+	int argpos;
+	unsigned st, ps;
+	int cnt=0, l=0;
+	int i;
+	char buf[sizeof(uintmax_t)*3+3+LDBL_MANT_DIG/4];
+	const char *prefix;
+	int t, pl;
+	wchar_t wc[2], *ws;
+	char mb[4];
+
+	for (;;) {
+		/* Update output count, end loop when fmt is exhausted */
+		if (cnt >= 0) {
+			if (l > INT_MAX - cnt) {
+				errno = EOVERFLOW;
+				cnt = -1;
+			} else cnt += l;
+		}
+		if (!*s) break;
+
+		/* Handle literal text and %% format specifiers */
+		for (a=s; *s && *s!='%'; s++);
+		for (z=s; s[0]=='%' && s[1]=='%'; z++, s+=2);
+		l = z-a;
+		if (f) out(f, a, l);
+		if (l) continue;
+
+		if (isdigit(s[1]) && s[2]=='$') {
+			l10n=1;
+			argpos = s[1]-'0';
+			s+=3;
+		} else {
+			argpos = -1;
+			s++;
+		}
+
+		/* Read modifier flags */
+		for (fl=0; (unsigned)*s-' '<32 && (FLAGMASK&(1U<<*s-' ')); s++)
+			fl |= 1U<<*s-' ';
+
+		/* Read field width */
+		if (*s=='*') {
+			if (isdigit(s[1]) && s[2]=='$') {
+				l10n=1;
+				nl_type[s[1]-'0'] = INT;
+				w = nl_arg[s[1]-'0'].i;
+				s+=3;
+			} else if (!l10n) {
+				w = f ? va_arg(*ap, int) : 0;
+				s++;
+			} else return -1;
+			if (w<0) fl|=LEFT_ADJ, w=-w;
+		} else if ((w=getint(&s))<0) return -1;
+
+		/* Read precision */
+		if (*s=='.' && s[1]=='*') {
+			if (isdigit(s[2]) && s[3]=='$') {
+				nl_type[s[2]-'0'] = INT;
+				p = nl_arg[s[2]-'0'].i;
+				s+=4;
+			} else if (!l10n) {
+				p = f ? va_arg(*ap, int) : 0;
+				s+=2;
+			} else return -1;
+		} else if (*s=='.') {
+			s++;
+			p = getint(&s);
+		} else p = -1;
+
+		/* Format specifier state machine */
+		st=0;
+		do {
+			if (OOB(*s)) return -1;
+			ps=st;
+			st=states[st]S(*s++);
+		} while (st-1<STOP);
+		if (!st) return -1;
+
+		/* Check validity of argument type (nl/normal) */
+		if (st==NOARG) {
+			if (argpos>=0) return -1;
+			else if (!f) continue;
+		} else {
+			if (argpos>=0) nl_type[argpos]=st, arg=nl_arg[argpos];
+			else if (f) pop_arg(&arg, st, ap);
+			else return 0;
+		}
+
+		if (!f) continue;
+
+		z = buf + sizeof(buf);
+		prefix = "-+   0X0x";
+		pl = 0;
+		t = s[-1];
+
+		/* Transform ls,lc -> S,C */
+		if (ps && (t&15)==3) t&=~32;
+
+		/* - and 0 flags are mutually exclusive */
+		if (fl & LEFT_ADJ) fl &= ~ZERO_PAD;
+
+		switch(t) {
+		case 'n':
+			switch(ps) {
+			case BARE: *(int *)arg.p = cnt; break;
+			case LPRE: *(long *)arg.p = cnt; break;
+			case LLPRE: *(long long *)arg.p = cnt; break;
+			case HPRE: *(unsigned short *)arg.p = cnt; break;
+			case HHPRE: *(unsigned char *)arg.p = cnt; break;
+			case ZTPRE: *(size_t *)arg.p = cnt; break;
+			case JPRE: *(uintmax_t *)arg.p = cnt; break;
+			}
+			continue;
+		case 'p':
+			p = MAX(p, 2*sizeof(void*));
+			t = 'x';
+			fl |= ALT_FORM;
+		case 'x': case 'X':
+			a = fmt_x(arg.i, z, t&32);
+			if (arg.i && (fl & ALT_FORM)) prefix+=(t>>4), pl=2;
+			if (0) {
+		case 'o':
+			a = fmt_o(arg.i, z);
+			if ((fl&ALT_FORM) && arg.i) prefix+=5, pl=1;
+			} if (0) {
+		case 'd': case 'i':
+			pl=1;
+			if (arg.i>INTMAX_MAX) {
+				arg.i=-arg.i;
+			} else if (fl & MARK_POS) {
+				prefix++;
+			} else if (fl & PAD_POS) {
+				prefix+=2;
+			} else pl=0;
+		case 'u':
+			a = fmt_u(arg.i, z);
+			}
+			if (p>=0) fl &= ~ZERO_PAD;
+			if (!arg.i && !p) {
+				a=z;
+				break;
+			}
+			p = MAX(p, z-a + !arg.i);
+			break;
+		case 'c':
+			*(a=z-(p=1))=arg.i;
+			fl &= ~ZERO_PAD;
+			break;
+		case 'm':
+			if (1) a = strerror(errno); else
+		case 's':
+			a = arg.p ? arg.p : "(null)";
+			z = memchr(a, 0, p);
+			if (!z) z=a+p;
+			else p=z-a;
+			fl &= ~ZERO_PAD;
+			break;
+		case 'C':
+			wc[0] = arg.i;
+			wc[1] = 0;
+			arg.p = wc;
+			p = -1;
+		case 'S':
+			ws = arg.p;
+			for (i=l=0; i<0U+p && *ws && (l=wctomb(mb, *ws++))>=0 && l<=0U+p-i; i+=l);
+			if (l<0) return -1;
+			p = i;
+			pad(f, ' ', w, p, fl);
+			ws = arg.p;
+			for (i=0; i<0U+p && *ws && i+(l=wctomb(mb, *ws++))<=p; i+=l)
+				out(f, mb, l);
+			pad(f, ' ', w, p, fl^LEFT_ADJ);
+			l = w>p ? w : p;
+			continue;
+		case 'e': case 'f': case 'g': case 'a':
+		case 'E': case 'F': case 'G': case 'A':
+			l = fmt_fp(f, arg.f, w, p, fl, t);
+			continue;
+		}
+
+		if (p < z-a) p = z-a;
+		if (w < pl+p) w = pl+p;
+
+		pad(f, ' ', w, pl+p, fl);
+		out(f, prefix, pl);
+		pad(f, '0', w, pl+p, fl^ZERO_PAD);
+		pad(f, '0', p, z-a, 0);
+		out(f, a, z-a);
+		pad(f, ' ', w, pl+p, fl^LEFT_ADJ);
+
+		l = w;
+	}
+
+	if (f) return cnt;
+	if (!l10n) return 0;
+
+	for (i=1; i<=NL_ARGMAX && nl_type[i]; i++)
+		pop_arg(nl_arg+i, nl_type[i], ap);
+	for (; i<=NL_ARGMAX && !nl_type[i]; i++);
+	if (i<=NL_ARGMAX) return -1;
+	return 1;
+}
+
+//int vfprintf(FILE *restrict f, const char *restrict fmt, va_list ap)
+int MUSL_vfprintf(FILE *restrict f, const char *restrict fmt, va_list ap) /// XXX Emscripten: Only use musl-specific vfprintf when called from within sprintf.
+{
+	va_list ap2;
+	int nl_type[NL_ARGMAX+1] = {0};
+	union arg nl_arg[NL_ARGMAX+1];
+	unsigned char internal_buf[80], *saved_buf = 0;
+	int ret;
+
+	va_copy(ap2, ap);
+	if (printf_core(0, fmt, &ap2, nl_arg, nl_type) < 0) return -1;
+
+	FLOCK(f);
+	if (!f->buf_size) {
+		saved_buf = f->buf;
+		f->wpos = f->wbase = f->buf = internal_buf;
+		f->buf_size = sizeof internal_buf;
+		f->wend = internal_buf + sizeof internal_buf;
+	}
+	ret = printf_core(f, fmt, &ap2, nl_arg, nl_type);
+	if (saved_buf) {
+		f->write(f, 0, 0);
+		if (!f->wpos) ret = -1;
+		f->buf = saved_buf;
+		f->buf_size = 0;
+		f->wpos = f->wbase = f->wend = 0;
+	}
+	FUNLOCK(f);
+	va_end(ap2);
+	return ret;
+}
diff --git a/system/lib/libc/musl/src/stdio/vsnprintf.c b/system/lib/libc/musl/src/stdio/vsnprintf.c
new file mode 100644
index 00000000..9dcc84af
--- /dev/null
+++ b/system/lib/libc/musl/src/stdio/vsnprintf.c
@@ -0,0 +1,45 @@
+#include "stdio_impl.h"
+#include <limits.h>
+#include <string.h>
+#include <errno.h>
+#include <stdint.h>
+
+static size_t sn_write(FILE *f, const unsigned char *s, size_t l)
+{
+	size_t k = f->wend - f->wpos;
+	if (k > l) k = l;
+	memcpy(f->wpos, s, k);
+	f->wpos += k;
+	/* pretend to succeed, but discard extra data */
+	return l;
+}
+
+// XXX Emscripten Call to musl-specific vfprintf for better asm.js performance, instead of the handwritten js function.
+#define vfprintf MUSL_vfprintf
+
+int vsnprintf(char *restrict s, size_t n, const char *restrict fmt, va_list ap)
+{
+	int r;
+	char b;
+	FILE f = { .lbf = EOF, .write = sn_write, .lock = -1 };
+
+	if (n-1 > INT_MAX-1) {
+		if (n) {
+			errno = EOVERFLOW;
+			return -1;
+		}
+		s = &b;
+		n = 1;
+	}
+
+	/* Ensure pointers don't wrap if "infinite" n is passed in */
+	if (n > (char *)0+SIZE_MAX-s-1) n = (char *)0+SIZE_MAX-s-1;
+	f.buf_size = n;
+	f.buf = f.wpos = (void *)s;
+	f.wbase = f.wend = (void *)(s+n);
+	r = vfprintf(&f, fmt, ap);
+
+	/* Null-terminate, overwriting last char if dest buffer is full */
+	if (n) f.wpos[-(f.wpos == f.wend)] = 0;
+	return r;
+}
diff --git a/system/lib/libc/musl/src/stdio/vsprintf.c b/system/lib/libc/musl/src/stdio/vsprintf.c
new file mode 100644
index 00000000..c57349d4
--- /dev/null
+++ b/system/lib/libc/musl/src/stdio/vsprintf.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+#include <limits.h>
+
+int vsprintf(char *restrict s, const char *restrict fmt, va_list ap)
+{
+	return vsnprintf(s, INT_MAX, fmt, ap);
+}
diff --git a/system/lib/libcextra.symbols b/system/lib/libcextra.symbols
index 45bbd3b9..32fb23e1 100644
--- a/system/lib/libcextra.symbols
+++ b/system/lib/libcextra.symbols
@@ -21,6 +21,7 @@
          T __wcscoll_l
          T __wcsxfrm_l
          W __wctype_l
+         T asprintf
          T atoll
          T bcmp
          T bcopy
@@ -33,6 +34,9 @@
          T fcvt
          T fputwc
          W fputwc_unlocked
+         T frexp
+         T frexpf
+         T frexpl
          T fwprintf
          T gcvt
          T getopt
@@ -163,6 +167,7 @@
          T strverscmp
          T strxfrm
          W strxfrm_l
+         T sprintf
          T swprintf
          T tgamma
          T tgammaf
@@ -177,11 +182,15 @@
          T towlower_l
          T towupper
          T towupper_l
+         T vasprintf
          T verr
          T verrx
          T MUSL_vfscanf
          T vsscanf
+         T MUSL_vfprintf
          T vfwprintf
+         T vsnprintf
+         T vsprintf
          T vswprintf
          T vwarn
          T vwarnx
diff --git a/tools/system_libs.py b/tools/system_libs.py
index 7e2b1f02..d6b44efb 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -199,6 +199,9 @@ def calculate(temp_files, in_temp, stdout, stderr):
         '__cosdf.c',
         '__sin.c',
         '__sindf.c',
+        'frexp.c',
+        'frexpf.c',
+        'frexpl.c',
         'ilogb.c',
         'ilogbf.c',
         'ilogbl.c',
@@ -250,6 +253,7 @@ def calculate(temp_files, in_temp, stdout, stderr):
        ]],
        ['stdio', [
         '__string_read.c',
+        'asprintf.c',
         'fwprintf.c',
         'swprintf.c',
         'vfwprintf.c',
@@ -258,8 +262,14 @@ def calculate(temp_files, in_temp, stdout, stderr):
         'wprintf.c',
         'fputwc.c',
         'fputws.c',
+        'fwrite.c',
+        'sprintf.c',
         'sscanf.c',
+        'vasprintf.c',
+        'vfprintf.c',
         'vfscanf.c',
+        'vsnprintf.c',
+        'vsprintf.c',
         'vsscanf.c',
        ]],
        ['stdlib', [