auto import from //depot/cupcake/@135843
diff --git a/libc/stdlib/strtoimax.c b/libc/stdlib/strtoimax.c
new file mode 100644
index 0000000..a742eb9
--- /dev/null
+++ b/libc/stdlib/strtoimax.c
@@ -0,0 +1,171 @@
+/* $OpenBSD: strtoimax.c,v 1.1 2006/01/13 17:58:09 millert Exp $ */
+
+/*-
+ * Copyright (c) 1992 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ * 3. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
+ */
+
+#include <ctype.h>
+#include <errno.h>
+#include <inttypes.h>
+
+/*
+ * Convert a string to an intmax_t
+ *
+ * Ignores `locale' stuff. Assumes that the upper and lower case
+ * alphabets and digits are each contiguous.
+ */
+intmax_t
+strtoimax(const char *nptr, char **endptr, int base)
+{
+ const char *s;
+ intmax_t acc, cutoff;
+ int c;
+ int neg, any, cutlim;
+
+ /*
+ * Skip white space and pick up leading +/- sign if any.
+ * If base is 0, allow 0x for hex and 0 for octal, else
+ * assume decimal; if base is already 16, allow 0x.
+ */
+ s = nptr;
+ do {
+ c = (unsigned char) *s++;
+ } while (isspace(c));
+ if (c == '-') {
+ neg = 1;
+ c = *s++;
+ } else {
+ neg = 0;
+ if (c == '+')
+ c = *s++;
+ }
+ if ((base == 0 || base == 16) &&
+ c == '0' && (*s == 'x' || *s == 'X')) {
+ c = s[1];
+ s += 2;
+ base = 16;
+ }
+ if (base == 0)
+ base = c == '0' ? 8 : 10;
+
+ /*
+ * Compute the cutoff value between legal numbers and illegal
+ * numbers. That is the largest legal value, divided by the
+ * base. An input number that is greater than this value, if
+ * followed by a legal input character, is too big. One that
+ * is equal to this value may be valid or not; the limit
+ * between valid and invalid numbers is then based on the last
+ * digit. For instance, if the range for intmax_t is
+ * [-9223372036854775808..9223372036854775807] and the input base
+ * is 10, cutoff will be set to 922337203685477580 and cutlim to
+ * either 7 (neg==0) or 8 (neg==1), meaning that if we have
+ * accumulated a value > 922337203685477580, or equal but the
+ * next digit is > 7 (or 8), the number is too big, and we will
+ * return a range error.
+ *
+ * Set any if any `digits' consumed; make it negative to indicate
+ * overflow.
+ */
+
+ /* BIONIC: avoid division and module for common cases */
+#define CASE_BASE(x) \
+ case x: \
+ if (neg) { \
+ cutlim = INTMAX_MIN % x; \
+ cutoff = INTMAX_MIN / x; \
+ } else { \
+ cutlim = INTMAX_MAX % x; \
+ cutoff = INTMAX_MAX / x; \
+ }; \
+ break
+
+ switch (base) {
+ case 4:
+ if (neg) {
+ cutlim = (int)(INTMAX_MIN % 4);
+ cutoff = INTMAX_MIN / 4;
+ } else {
+ cutlim = (int)(INTMAX_MAX % 4);
+ cutoff = INTMAX_MAX / 4;
+ }
+ break;
+
+ CASE_BASE(8);
+ CASE_BASE(10);
+ CASE_BASE(16);
+ default:
+ cutoff = neg ? INTMAX_MIN : INTMAX_MAX;
+ cutlim = cutoff % base;
+ cutoff /= base;
+ }
+#undef CASE_BASE
+
+ if (neg) {
+ if (cutlim > 0) {
+ cutlim -= base;
+ cutoff += 1;
+ }
+ cutlim = -cutlim;
+ }
+ for (acc = 0, any = 0;; c = (unsigned char) *s++) {
+ if (isdigit(c))
+ c -= '0';
+ else if (isalpha(c))
+ c -= isupper(c) ? 'A' - 10 : 'a' - 10;
+ else
+ break;
+ if (c >= base)
+ break;
+ if (any < 0)
+ continue;
+ if (neg) {
+ if (acc < cutoff || (acc == cutoff && c > cutlim)) {
+ any = -1;
+ acc = INTMAX_MIN;
+ errno = ERANGE;
+ } else {
+ any = 1;
+ acc *= base;
+ acc -= c;
+ }
+ } else {
+ if (acc > cutoff || (acc == cutoff && c > cutlim)) {
+ any = -1;
+ acc = INTMAX_MAX;
+ errno = ERANGE;
+ } else {
+ any = 1;
+ acc *= base;
+ acc += c;
+ }
+ }
+ }
+ if (endptr != 0)
+ *endptr = (char *) (any ? s - 1 : nptr);
+ return (acc);
+}