diff --git a/libc/bionic/debug_format.cpp b/libc/bionic/debug_format.cpp
new file mode 100644
index 0000000..e8d6a45
--- /dev/null
+++ b/libc/bionic/debug_format.cpp
@@ -0,0 +1,634 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+// Temporarily disable _FORTIFY_SOURCE to get this code to
+// compile under GCC 4.7
+#undef _FORTIFY_SOURCE
+
+#include "debug_format.h"
+
+#include <assert.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+
+/* define UNIT_TESTS to build this file as a single executable that runs
+ * the formatter's unit tests
+ */
+#define xxUNIT_TESTS
+
+/*** Generic output sink
+ ***/
+
+struct Out {
+  void *opaque;
+  void (*send)(void *opaque, const char *data, int len);
+};
+
+static void out_send(Out *o, const char *data, size_t len) {
+    o->send(o->opaque, data, (int)len);
+}
+
+static void
+out_send_repeat(Out *o, char ch, int count)
+{
+    char pad[8];
+    const int padSize = (int)sizeof(pad);
+
+    memset(pad, ch, sizeof(pad));
+    while (count > 0) {
+        int avail = count;
+        if (avail > padSize) {
+            avail = padSize;
+        }
+        o->send(o->opaque, pad, avail);
+        count -= avail;
+    }
+}
+
+/* forward declaration */
+static void out_vformat(Out* o, const char* format, va_list args);
+
+/*** Bounded buffer output
+ ***/
+
+struct BufOut {
+  Out out[1];
+  char *buffer;
+  char *pos;
+  char *end;
+  int total;
+};
+
+static void buf_out_send(void *opaque, const char *data, int len) {
+    BufOut *bo = reinterpret_cast<BufOut*>(opaque);
+
+    if (len < 0) {
+        len = strlen(data);
+    }
+
+    bo->total += len;
+
+    while (len > 0) {
+        int avail = bo->end - bo->pos;
+        if (avail == 0)
+            break;
+        if (avail > len)
+            avail = len;
+        memcpy(bo->pos, data, avail);
+        bo->pos += avail;
+        bo->pos[0] = '\0';
+        len -= avail;
+    }
+}
+
+static Out*
+buf_out_init(BufOut *bo, char *buffer, size_t size)
+{
+    if (size == 0)
+        return NULL;
+
+    bo->out->opaque = bo;
+    bo->out->send   = buf_out_send;
+    bo->buffer      = buffer;
+    bo->end         = buffer + size - 1;
+    bo->pos         = bo->buffer;
+    bo->pos[0]      = '\0';
+    bo->total       = 0;
+
+    return bo->out;
+}
+
+static int
+buf_out_length(BufOut *bo)
+{
+    return bo->total;
+}
+
+static int
+vformat_buffer(char *buff, size_t buffsize, const char *format, va_list args)
+{
+    BufOut bo;
+    Out *out;
+
+    out = buf_out_init(&bo, buff, buffsize);
+    if (out == NULL)
+        return 0;
+
+    out_vformat(out, format, args);
+
+    return buf_out_length(&bo);
+}
+
+int __libc_format_buffer(char* buffer, size_t buffer_size, const char* format, ...) {
+  va_list args;
+  va_start(args, format);
+  int result = vformat_buffer(buffer, buffer_size, format, args);
+  va_end(args);
+  return result;
+}
+
+
+/*** File descriptor output
+ ***/
+
+struct FdOut {
+  Out out[1];
+  int fd;
+  int total;
+};
+
+static void
+fd_out_send(void *opaque, const char *data, int len)
+{
+    FdOut *fdo = reinterpret_cast<FdOut*>(opaque);
+
+    if (len < 0)
+        len = strlen(data);
+
+    while (len > 0) {
+        int ret = write(fdo->fd, data, len);
+        if (ret < 0) {
+            if (errno == EINTR)
+                continue;
+            break;
+        }
+        data += ret;
+        len -= ret;
+        fdo->total += ret;
+    }
+}
+
+static Out*
+fd_out_init(FdOut *fdo, int  fd)
+{
+    fdo->out->opaque = fdo;
+    fdo->out->send = fd_out_send;
+    fdo->fd = fd;
+    fdo->total = 0;
+
+    return fdo->out;
+}
+
+static int
+fd_out_length(FdOut *fdo)
+{
+    return fdo->total;
+}
+
+
+int __libc_format_fd(int fd, const char* format, ...) {
+  FdOut fdo;
+  Out* out = fd_out_init(&fdo, fd);
+  if (out == NULL) {
+    return 0;
+  }
+
+  va_list args;
+  va_start(args, format);
+  out_vformat(out, format, args);
+  va_end(args);
+
+  return fd_out_length(&fdo);
+}
+
+/*** Log output
+ ***/
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/uio.h>
+
+int __libc_format_log_va_list(int priority, const char* tag, const char* fmt, va_list args) {
+  char buf[1024];
+  int result = vformat_buffer(buf, sizeof buf, fmt, args);
+
+  static int log_fd = -1;
+  if (log_fd == -1) {
+    log_fd = open("/dev/log/main", O_WRONLY);
+    if (log_fd == -1) {
+      return result;
+    }
+  }
+
+  struct iovec vec[3];
+  vec[0].iov_base = (unsigned char *) &priority;
+  vec[0].iov_len = 1;
+  vec[1].iov_base = (void *) tag;
+  vec[1].iov_len = strlen(tag) + 1;
+  vec[2].iov_base = (void *) buf;
+  vec[2].iov_len = strlen(buf) + 1;
+
+  TEMP_FAILURE_RETRY(writev(log_fd, vec, 3));
+
+  return result;
+}
+
+int __libc_format_log(int priority, const char* tag, const char* format, ...) {
+  va_list args;
+  va_start(args, format);
+  int result = __libc_format_log_va_list(priority, tag, format, args);
+  va_end(args);
+  return result;
+}
+
+/*** formatted output implementation
+ ***/
+
+/* Parse a decimal string from 'format + *ppos',
+ * return the value, and writes the new position past
+ * the decimal string in '*ppos' on exit.
+ *
+ * NOTE: Does *not* handle a sign prefix.
+ */
+static unsigned
+parse_decimal(const char *format, int *ppos)
+{
+    const char* p = format + *ppos;
+    unsigned result = 0;
+
+    for (;;) {
+        int ch = *p;
+        unsigned d = (unsigned)(ch - '0');
+
+        if (d >= 10U)
+            break;
+
+        result = result*10 + d;
+        p++;
+    }
+    *ppos = p - format;
+    return result;
+}
+
+// Writes number 'value' in base 'base' into buffer 'buf' of size 'buf_size' bytes.
+// Assumes that buf_size > 0.
+static void format_number(char* buf, size_t buf_size, uint64_t value, int base, bool caps) {
+  char* p = buf;
+  char* end = buf + buf_size - 1;
+
+  // Generate digit string in reverse order.
+  while (value) {
+    unsigned d = value % base;
+    value /= base;
+    if (p != end) {
+      char ch;
+      if (d < 10) {
+        ch = '0' + d;
+      } else {
+        ch = (caps ? 'A' : 'a') + (d - 10);
+      }
+      *p++ = ch;
+    }
+  }
+
+  // Special case for 0.
+  if (p == buf) {
+    if (p != end) {
+      *p++ = '0';
+    }
+  }
+  *p = '\0';
+
+  // Reverse digit string in-place.
+  size_t length = p - buf;
+  for (size_t i = 0, j = length - 1; i < j; ++i, --j) {
+    char ch = buf[i];
+    buf[i] = buf[j];
+    buf[j] = ch;
+  }
+}
+
+/* Write an integer (octal or decimal) into a buffer, assumes buffsize > 2 */
+static void
+format_integer(char *buffer, size_t buffsize, uint64_t value, int base, int isSigned)
+{
+    // TODO: this is incorrect for MIN_INT.
+    if (isSigned && (int64_t)value < 0) {
+        buffer[0] = '-';
+        buffer += 1;
+        buffsize -= 1;
+        value = (uint64_t)(-(int64_t)value);
+    }
+
+    format_number(buffer, buffsize, value, base, false);
+}
+
+// Assumes buf_size > 2.
+static void format_hex(char* buf, size_t buf_size, uint64_t value, bool caps) {
+  format_number(buf, buf_size, value, 16, caps);
+}
+
+
+/* Perform formatted output to an output target 'o' */
+static void
+out_vformat(Out *o, const char *format, va_list args)
+{
+    int nn = 0;
+
+    for (;;) {
+        int mm;
+        int padZero = 0;
+        int padLeft = 0;
+        char sign = '\0';
+        int width = -1;
+        int prec  = -1;
+        size_t bytelen = sizeof(int);
+        const char*  str;
+        int slen;
+        char buffer[32];  /* temporary buffer used to format numbers */
+
+        char  c;
+
+        /* first, find all characters that are not 0 or '%' */
+        /* then send them to the output directly */
+        mm = nn;
+        do {
+            c = format[mm];
+            if (c == '\0' || c == '%')
+                break;
+            mm++;
+        } while (1);
+
+        if (mm > nn) {
+            out_send(o, format+nn, mm-nn);
+            nn = mm;
+        }
+
+        /* is this it ? then exit */
+        if (c == '\0')
+            break;
+
+        /* nope, we are at a '%' modifier */
+        nn++;  // skip it
+
+        /* parse flags */
+        for (;;) {
+            c = format[nn++];
+            if (c == '\0') {  /* single trailing '%' ? */
+                c = '%';
+                out_send(o, &c, 1);
+                return;
+            }
+            else if (c == '0') {
+                padZero = 1;
+                continue;
+            }
+            else if (c == '-') {
+                padLeft = 1;
+                continue;
+            }
+            else if (c == ' ' || c == '+') {
+                sign = c;
+                continue;
+            }
+            break;
+        }
+
+        /* parse field width */
+        if ((c >= '0' && c <= '9')) {
+            nn --;
+            width = (int)parse_decimal(format, &nn);
+            c = format[nn++];
+        }
+
+        /* parse precision */
+        if (c == '.') {
+            prec = (int)parse_decimal(format, &nn);
+            c = format[nn++];
+        }
+
+        /* length modifier */
+        switch (c) {
+        case 'h':
+            bytelen = sizeof(short);
+            if (format[nn] == 'h') {
+                bytelen = sizeof(char);
+                nn += 1;
+            }
+            c = format[nn++];
+            break;
+        case 'l':
+            bytelen = sizeof(long);
+            if (format[nn] == 'l') {
+                bytelen = sizeof(long long);
+                nn += 1;
+            }
+            c = format[nn++];
+            break;
+        case 'z':
+            bytelen = sizeof(size_t);
+            c = format[nn++];
+            break;
+        case 't':
+            bytelen = sizeof(ptrdiff_t);
+            c = format[nn++];
+            break;
+        default:
+            ;
+        }
+
+        /* conversion specifier */
+        if (c == 's') {
+            /* string */
+            str = va_arg(args, const char*);
+        } else if (c == 'c') {
+            /* character */
+            /* NOTE: char is promoted to int when passed through the stack */
+            buffer[0] = (char) va_arg(args, int);
+            buffer[1] = '\0';
+            str = buffer;
+        } else if (c == 'p') {
+            uint64_t  value = (uintptr_t) va_arg(args, void*);
+            buffer[0] = '0';
+            buffer[1] = 'x';
+            format_hex(buffer + 2, sizeof buffer-2, value, false);
+            str = buffer;
+        } else {
+            /* integers - first read value from stack */
+            uint64_t value;
+            int isSigned = (c == 'd' || c == 'i' || c == 'o');
+
+            /* NOTE: int8_t and int16_t are promoted to int when passed
+             *       through the stack
+             */
+            switch (bytelen) {
+            case 1: value = (uint8_t)  va_arg(args, int); break;
+            case 2: value = (uint16_t) va_arg(args, int); break;
+            case 4: value = va_arg(args, uint32_t); break;
+            case 8: value = va_arg(args, uint64_t); break;
+            default: return;  /* should not happen */
+            }
+
+            /* sign extension, if needed */
+            if (isSigned) {
+                int shift = 64 - 8*bytelen;
+                value = (uint64_t)(((int64_t)(value << shift)) >> shift);
+            }
+
+            /* format the number properly into our buffer */
+            switch (c) {
+            case 'i': case 'd':
+                format_integer(buffer, sizeof buffer, value, 10, isSigned);
+                break;
+            case 'o':
+                format_integer(buffer, sizeof buffer, value, 8, isSigned);
+                break;
+            case 'x': case 'X':
+                format_hex(buffer, sizeof buffer, value, (c == 'X'));
+                break;
+            default:
+                buffer[0] = '\0';
+            }
+            /* then point to it */
+            str = buffer;
+        }
+
+        /* if we are here, 'str' points to the content that must be
+         * outputted. handle padding and alignment now */
+
+        slen = strlen(str);
+
+        if (sign != '\0' || prec != -1) {
+            __assert(__FILE__, __LINE__, "sign/precision unsupported");
+        }
+
+        if (slen < width && !padLeft) {
+            char padChar = padZero ? '0' : ' ';
+            out_send_repeat(o, padChar, width - slen);
+        }
+
+        out_send(o, str, slen);
+
+        if (slen < width && padLeft) {
+            char padChar = padZero ? '0' : ' ';
+            out_send_repeat(o, padChar, width - slen);
+        }
+    }
+}
+
+
+#ifdef UNIT_TESTS
+
+#include <stdio.h>
+
+static int   gFails = 0;
+
+#define  MARGIN  40
+
+#define  UTEST_CHECK(condition,message) \
+    printf("Checking %-*s: ", MARGIN, message); fflush(stdout); \
+    if (!(condition)) { \
+        printf("KO\n"); \
+        gFails += 1; \
+    } else { \
+        printf("ok\n"); \
+    }
+
+static void
+utest_BufOut(void)
+{
+    char buffer[16];
+    BufOut bo[1];
+    Out* out;
+    int ret;
+
+    buffer[0] = '1';
+    out = buf_out_init(bo, buffer, sizeof buffer);
+    UTEST_CHECK(buffer[0] == '\0', "buf_out_init clears initial byte");
+    out_send(out, "abc", 3);
+    UTEST_CHECK(!memcmp(buffer, "abc", 4), "out_send() works with BufOut");
+    out_send_repeat(out, 'X', 4);
+    UTEST_CHECK(!memcmp(buffer, "abcXXXX", 8), "out_send_repeat() works with BufOut");
+    buffer[sizeof buffer-1] = 'x';
+    out_send_repeat(out, 'Y', 2*sizeof(buffer));
+    UTEST_CHECK(buffer[sizeof buffer-1] == '\0', "overflows always zero-terminates");
+
+    out = buf_out_init(bo, buffer, sizeof buffer);
+    out_send_repeat(out, 'X', 2*sizeof(buffer));
+    ret = buf_out_length(bo);
+    UTEST_CHECK(ret == 2*sizeof(buffer), "correct size returned on overflow");
+}
+
+static void
+utest_expect(const char*  result, const char*  format, ...)
+{
+    va_list args;
+    BufOut bo[1];
+    char buffer[256];
+    Out* out = buf_out_init(bo, buffer, sizeof buffer);
+
+    printf("Checking %-*s: ", MARGIN, format); fflush(stdout);
+    va_start(args, format);
+    out_vformat(out, format, args);
+    va_end(args);
+
+    if (strcmp(result, buffer)) {
+        printf("KO. got '%s' expecting '%s'\n", buffer, result);
+        gFails += 1;
+    } else {
+        printf("ok. got '%s'\n", result);
+    }
+}
+
+int  main(void)
+{
+    utest_BufOut();
+    utest_expect("", "");
+    utest_expect("a", "a");
+    utest_expect("01234", "01234", "");
+    utest_expect("01234", "%s", "01234");
+    utest_expect("aabbcc", "aa%scc", "bb");
+    utest_expect("a", "%c", 'a');
+    utest_expect("1234", "%d", 1234);
+    utest_expect("-8123", "%d", -8123);
+    utest_expect("16", "%hd", 0x7fff0010);
+    utest_expect("16", "%hhd", 0x7fffff10);
+    utest_expect("68719476736", "%lld", 0x1000000000LL);
+    utest_expect("70000", "%ld", 70000);
+    utest_expect("0xb0001234", "%p", (void*)0xb0001234);
+    utest_expect("12ab", "%x", 0x12ab);
+    utest_expect("12AB", "%X", 0x12ab);
+    utest_expect("00123456", "%08x", 0x123456);
+    utest_expect("01234", "0%d", 1234);
+    utest_expect(" 1234", "%5d", 1234);
+    utest_expect("01234", "%05d", 1234);
+    utest_expect("    1234", "%8d", 1234);
+    utest_expect("1234    ", "%-8d", 1234);
+    utest_expect("abcdef     ", "%-11s", "abcdef");
+    utest_expect("something:1234", "%s:%d", "something", 1234);
+    utest_expect("005:5:05", "%03d:%d:%02d", 5, 5, 5);
+    utest_expect("5,0x0", "%d,%p", 5, NULL);
+    utest_expect("68719476736,6,7,8", "%lld,%d,%d,%d", 0x1000000000LL, 6, 7, 8);
+    return gFails != 0;
+}
+
+#endif /* UNIT_TESTS */