diff --git a/CMakeLists.txt b/CMakeLists.txt
index 71c6693..7333e3e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -140,6 +140,7 @@ set(SOURCES
   src/stdio/puts.c
   src/stdio/remove.c
   src/stdio/rewind.c
+  src/stdio/scanf/scan.c
   src/stdio/setbuf.c
   src/stdio/setvbuf.c
   src/stdio/snprintf.c
diff --git a/include/fxlibc/printf.h b/include/fxlibc/printf.h
index bac624e..a6b6c67 100644
--- a/include/fxlibc/printf.h
+++ b/include/fxlibc/printf.h
@@ -75,7 +75,6 @@ extern int __printf(
 	va_list *__args);
 
 
-
 /* Format extension API. */
 
 struct __printf_format {
@@ -84,12 +83,8 @@ struct __printf_format {
 	/* How much significant characters of data, meaning varies. */
 	int16_t precision;
 
-	/*
-	** Size specifier for integers (%o, %x, %i, %d, %u), is equal to the
-	** sizeof() of the targeted type. Also used for %lc.
-	*/
+	/* Size of targeted integer type (%o, %x, %i, %d, %u), in bytes */
 	uint8_t size;
-
 	/* (#) Alternative form: base prefixes, decimal point. */
 	uint8_t alternative :1;
 	/* ( ) Add a blank sign before nonnegative numbers. */
@@ -111,15 +106,14 @@ struct __printf_format {
 
 /*
 ** Type of format functions.
-** -> __spec is the specifier letter (eg. "d" in "%d")
-** -> __opts are the length, precision, sign, alignment, etc. options
+** -> __out specifies the output and is used when generating text
+** -> __fmt contains the format options and specifier letter
 ** -> __args is a pointer to the variable list of arguments to read from
 */
 typedef void __printf_formatter_t(
 	struct __printf_output *__out,
-	struct __printf_format *__opts,
-	va_list *__args
-);
+	struct __printf_format *__fmt,
+	va_list *__args);
 
 /*
 ** Register a new format.
@@ -127,10 +121,10 @@ typedef void __printf_formatter_t(
 ** The formatter designated by the specified lowercase or uppercase letter
 ** (eg 'p' or 'P') is registered. This functions allows overriding default
 ** formatters, but this is very much discouraged. Letters with special meaning
-** in the standard cannot be changed. A formatted can be removed of disabled by
+** in the standard cannot be changed. A formatter can be removed of disabled by
 ** registering NULL.
 **
-** Here are used characters in the C standard:
+** Here are the characters used/reserved in the C standard:
 **
 ** a: Hexadecimal floating-point      A: Hexadecimal floating-point
 ** b: _                               B: _
@@ -138,7 +132,7 @@ typedef void __printf_formatter_t(
 ** d: Decimal integer                 D: _
 ** e: Exponent floating-point         E: Exponent floating-point
 ** f: Floating-point                  F: Floating-point
-** g: General floating-point          G: General: floating-point
+** g: General floating-point          G: General floating-point
 ** h: short or char size              H: _
 ** i: Integer                         I: Locale-aware digits
 ** j: intmax_t size                   J: _
diff --git a/src/stdio/scanf/scan.c b/src/stdio/scanf/scan.c
new file mode 100644
index 0000000..1bc93ee
--- /dev/null
+++ b/src/stdio/scanf/scan.c
@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include "../stdio_p.h"
+#include "../../stdlib/stdlib_p.h"
+
+void __scanf_start(struct __scanf_input *__in)
+{
+
+    if(__in->fp)
+        __in->buffer = fgetc(__in->fp);
+    else {
+        __in->buffer = *__in->str;
+        __in->str += (__in->buffer != 0);
+    }
+}
+
+int __scanf_fetch(struct __scanf_input *__in)
+{
+	if(__in->fp)
+		return fgetc(__in->fp);
+
+	int c = *__in->str;
+	if(c == 0)
+		return EOF;
+	__in->str++;
+	return c;
+}
+
+void __scanf_end(struct __scanf_input *__in)
+{
+	if(__in->buffer == EOF)
+		return;
+
+	if(__in->fp)
+		ungetc(__in->buffer, __in->fp);
+	else
+		__in->str--;
+}
diff --git a/src/stdio/stdio_p.h b/src/stdio/stdio_p.h
new file mode 100644
index 0000000..150fc22
--- /dev/null
+++ b/src/stdio/stdio_p.h
@@ -0,0 +1,45 @@
+#ifndef __STDIO_P_H__
+# define __STDIO_P_H__
+
+#include <stdio.h>
+
+/*
+** General utilities for scanf(); we expose them here as we use subfunctions of
+** strto*() from <stdlib.h> to implement numerical specifiers.
+*/
+
+/*
+** Input for scanf; exactly one of str and fp must be non-NULL. We include a
+** single-character buffer for convenience for scanning functions to test the
+** next character, which can be flushed back by ungetc().
+*/
+struct __scanf_input {
+	char const * __restrict__ str;
+	FILE *fp;
+	int buffer;
+};
+
+/* Initialize the input by feeding the buffer byte. */
+void __scanf_start(struct __scanf_input *__in);
+
+/* Fetch the next byte from the input and return it (don't call directly). */
+int __scanf_fetch(struct __scanf_input *__in);
+
+/* Read the next byte while maintaining the buffer. */
+static inline int __scanf_in(struct __scanf_input *__in)
+{
+	int c = __in->buffer;
+	__in->buffer = __scanf_fetch(__in);
+	return c;
+}
+
+/* Peek the next byte without advancing. */
+static inline int __scanf_peek(struct __scanf_input *__in)
+{
+	return __in->buffer;
+}
+
+/* Close the input by unsending the buffer once finished. */
+void __scanf_end(struct __scanf_input *__in);
+
+#endif /* __STDIO_P_H__ */
diff --git a/src/stdlib/stdlib_p.h b/src/stdlib/stdlib_p.h
index 5831031..c368086 100644
--- a/src/stdlib/stdlib_p.h
+++ b/src/stdlib/stdlib_p.h
@@ -3,6 +3,7 @@
 
 #include <stdlib.h>
 #include <stdbool.h>
+#include "../stdio/stdio_p.h"
 
 /*
 ** Parse an integer from a string. This is the base function for strtol,
@@ -23,8 +24,7 @@
 ** expensive.
 */
 int __strto_int(
-	char const * restrict __ptr,
-	char ** restrict __endptr,
+	struct __scanf_input *__input,
 	int __base,
 	long *__outl,
 	long long *__outll,
@@ -39,10 +39,9 @@ int __strto_int(
 ** and outl is set.
 */
 int __strto_fp(
-   char const * restrict __ptr,
-   char ** restrict __endptr,
-   double *__out,
-   float *__outf,
-   long double *__outl);
+	struct __scanf_input *__input,
+	double *__out,
+	float *__outf,
+	long double *__outl);
 
 #endif /*__STDLIB_P_H__*/
diff --git a/src/stdlib/strto_fp.c b/src/stdlib/strto_fp.c
index d9b6cef..14e089e 100644
--- a/src/stdlib/strto_fp.c
+++ b/src/stdlib/strto_fp.c
@@ -1,3 +1,4 @@
+#include "stdlib_p.h"
 #include <stdlib.h>
 #include <stdbool.h>
 
@@ -37,12 +38,11 @@
 ** -> In hexadecimal notation, we read as many bits as the mantissa of a long
 **    double, then later multiply by a power of 2. There are no approximations.
 */
-static void parse_digits(char const * restrict *ptr0, bool *valid,
+static bool parse_digits(struct __scanf_input *input,
 	SIGNIFICAND_TYPE *digits, long *exponent, bool hexadecimal)
 {
-	char const *ptr = *ptr0;
 	bool dot_found = false;
-	int digits_found = 0;
+	int digits_found=0, c=0;
 
 	*digits = 0;
 	*exponent = 0;
@@ -53,13 +53,14 @@ static void parse_digits(char const * restrict *ptr0, bool *valid,
 	int dot_character = '.';
 	int exp_character = (hexadecimal ? 'p' : 'e');
 
-	for(int i = 0; isdigit(*ptr) || (hexadecimal && isxdigit(*ptr))
-		|| *ptr == dot_character; i++, ptr++) {
+	for(int i = 0; true; i++) {
+		c = __scanf_peek(input);
+		if(!(isdigit(c) ||
+		    (hexadecimal && isxdigit(c)) ||
+		    (c == dot_character && !dot_found))) break;
+		__scanf_in(input);
 
-		/* Allow only one dot in the string, stop at the second one */
-		if(*ptr == dot_character && dot_found) break;
-
-		if(*ptr == dot_character) {
+		if(c == dot_character) {
 			dot_found = true;
 			continue;
 		}
@@ -67,12 +68,12 @@ static void parse_digits(char const * restrict *ptr0, bool *valid,
 		/* Count digits only until SIGNIFICAND_DIGITS */
 		if(digits_found < max_digits) {
 			if(hexadecimal) {
-				int v = *ptr - '0';
-				if(!isdigit(*ptr)) v = tolower(*ptr)-'a'+10;
+				int v = c - '0';
+				if(!isdigit(c)) v = tolower(c) - 'a' + 10;
 				*digits = (*digits << 4) + v;
 			}
 			else {
-				*digits = (*digits * 10) + (*ptr - '0');
+				*digits = (*digits * 10) + (c - '0');
 			}
 		}
 		else (*exponent)++;
@@ -80,7 +81,7 @@ static void parse_digits(char const * restrict *ptr0, bool *valid,
 		if(dot_found) (*exponent)--;
 
 		/* But also round at the first discarded one */
-		if(digits_found == max_digits && *ptr >= '5')
+		if(digits_found == max_digits && c >= '5')
 			(*digits)++;
 
 		digits_found++;
@@ -88,46 +89,54 @@ static void parse_digits(char const * restrict *ptr0, bool *valid,
 
 	/* Require at least one digit to be present; if not, the whole string
 	   is considered invalid */
-	if(!digits_found) {
-		*valid = false;
-		return;
-	}
+	if(!digits_found)
+		return false;
 
 	/* In hexadecimal, each character is worth 4 bits of exponent */
 	if(hexadecimal) (*exponent) *= 4;
 
 	/* Parse exponent */
-	if(tolower(*ptr) == exp_character) {
-		char *end;
-		long e = strtol(ptr + 1, &end, 10);
+	if(tolower(__scanf_peek(input)) == exp_character) {
+		/* Hack: Restore the str pointer if this fails (which we
+		   cannot determine with a single lookahead) so that *endptr is
+		   set correctly */
+		struct __scanf_input backup = *input;
 
-		/* If an integer cannot be parsed, ignore the 'e...' part */
-		if(end != ptr + 1) {
-			ptr = end;
+		__scanf_in(input);
+		long e = 0;
+		if(__strto_int(input, 10, &e, NULL, false) == 0)
 			*exponent += e;
-		}
+		else
+			*input = backup;
 	}
 
-	*ptr0 = ptr;
-	*valid = true;
+	return true;
 }
 
-int __strto_fp(char const * restrict ptr, char ** restrict endptr, double *out,
-	float *outf, long double *outl)
+static bool expect(struct __scanf_input *input, char const *sequence)
 {
-	/* Save the value of ptr in endptr, in case format is invalid */
-	if(endptr) *endptr = (char *)ptr;
+	for(int i = 0; sequence[i]; i++) {
+		int c = __scanf_in(input);
+		if(tolower(c) != tolower(sequence[i]))
+			return false;
+	}
+	return true;
+}
 
+int __strto_fp(struct __scanf_input *input, double *out, float *outf,
+	long double *outl)
+{
 	/* Skip initial whitespace */
-	while(isspace(*ptr)) ptr++;
+	while(isspace(__scanf_peek(input))) __scanf_in(input);
 
 	/* Read optional sign */
 	bool negative = false;
-	if(*ptr == '-') negative = true;
-	if(*ptr == '-' || *ptr == '+') ptr++;
+	int sign = __scanf_peek(input);
+	if(sign == '-') negative = true;
+	if(sign == '-' || sign == '+') __scanf_in(input);
 
 	int errno_value = 0;
-	bool valid = true;
+	bool valid = false;
 
 	/* Result variable */
 	if(out)  *out = 0.0;
@@ -135,47 +144,64 @@ int __strto_fp(char const * restrict ptr, char ** restrict endptr, double *out,
 	if(outl) *outl = 0.0l;
 
 	/* NaN possibly with an argument */
-	if(!strncasecmp(ptr, "nan", 3)) {
-		char const *arg = "";
-		ptr += 3;
-		if(ptr[0] == '(') {
-			arg = ptr + 1;
-			do ptr++;
-			while(ptr[-1] != ')');
+	if(tolower(__scanf_peek(input)) == 'n') {
+		if(!expect(input, "nan"))
+			return EINVAL;
+
+		/* Get the argument for up to 32 bytes */
+		char arg[32];
+		int i = 0;
+
+		if(__scanf_peek(input) == '(') {
+			while(i < 31) {
+				int c = __scanf_in(input);
+				if(c == ')') break;
+				arg[i++] = c;
+			}
+			arg[i] = 0;
 		}
 
 		if(out)  *out  = __builtin_nan(arg);
 		if(outf) *outf = __builtin_nanf(arg);
 		if(outl) *outl = __builtin_nanl(arg);
+		valid = true;
 	}
-	/* Infinity */
-	else if(!strncasecmp(ptr, "infinity", 8)) {
+	else if(tolower(__scanf_peek(input)) == 'i') {
+		if(!expect(input, "inf"))
+			return EINVAL;
+		if(tolower(__scanf_peek(input)) == 'i' &&
+		   !expect(input, "inity"))
+			return EINVAL;
 		if(out)  *out  = __builtin_inf();
 		if(outf) *outf = __builtin_inff();
 		if(outl) *outl = __builtin_infl();
-		ptr += 8;
-	}
-	else if(!strncasecmp(ptr, "inf", 3)) {
-		if(out)  *out  = __builtin_inf();
-		if(outf) *outf = __builtin_inff();
-		if(outl) *outl = __builtin_infl();
-		ptr += 3;
+		valid = true;
 	}
 	else {
 		SIGNIFICAND_TYPE digits = 0;
 		long e = 0;
 
-		if(ptr[0] == '0' && tolower(ptr[1]) == 'x') {
-			ptr += 2;
-			parse_digits(&ptr, &valid, &digits, &e, true);
+		/* Check for the 0x prefix. Skipping a 0 if we start with 0 but
+		   not 0x isn't a problem. */
+		bool hexa = false;
+		if(__scanf_peek(input) == '0') {
+			__scanf_in(input);
+			if(tolower(__scanf_peek(input)) == 'x') {
+				__scanf_in(input);
+				hexa = true;
+			}
+			/* Count the 0 as a digit */
+			else valid = true;
+		}
 
+		if(hexa) {
+			valid |= parse_digits(input, &digits, &e, true);
 			if(out)  *out  = (double)digits * exp2(e);
 			if(outf) *outf = (float)digits * exp2f(e);
 			if(outl) *outl = (long double)digits * exp2l(e);
 		}
 		else {
-			parse_digits(&ptr, &valid, &digits, &e, false);
-
+			valid |= parse_digits(input, &digits, &e, false);
 			if(out)  *out  = (double)digits * pow(10, e);
 			if(outf) *outf = (float)digits * powf(10, e);
 			if(outl) *outl = (long double)digits * powl(10, e);
@@ -200,8 +226,5 @@ int __strto_fp(char const * restrict ptr, char ** restrict endptr, double *out,
 		if(outl) *outl = -(*outl);
 	}
 
-	/* Save the result pointer */
-	if(endptr && valid) *endptr = (char *)ptr;
-
-	return errno_value;
+	return valid ? errno_value : EINVAL;
 }
diff --git a/src/stdlib/strto_int.c b/src/stdlib/strto_int.c
index 8b6d298..6bbb20d 100644
--- a/src/stdlib/strto_int.c
+++ b/src/stdlib/strto_int.c
@@ -4,19 +4,17 @@
 #include <errno.h>
 #include <limits.h>
 
-int __strto_int(char const * restrict ptr, char ** restrict endptr, int base,
-	long *outl, long long *outll, bool use_unsigned)
+int __strto_int(struct __scanf_input *input, int base, long *outl,
+	long long *outll, bool use_unsigned)
 {
-	/* Save the value of ptr in endptr now in case the format is invalid */
-	if(endptr) *endptr = (char *)ptr;
-
 	/* Skip initial whitespace */
-	while(isspace(*ptr)) ptr++;
+	while(isspace(__scanf_peek(input))) __scanf_in(input);
 
 	/* Accept a sign character */
 	bool negative = false;
-	if(*ptr == '-') negative = true;
-	if(*ptr == '-' || *ptr == '+') ptr++;
+	int sign = __scanf_peek(input);
+	if(sign == '-') negative = true;
+	if(sign == '-' || sign == '+') __scanf_in(input);
 
 	/* Use unsigned variables as only these have defined overflow */
 	unsigned long xl = 0;
@@ -26,29 +24,34 @@ int __strto_int(char const * restrict ptr, char ** restrict endptr, int base,
 	bool valid = false;
 
 	/* Read prefixes and determine base */
-	if((base == 0 || base == 16) && ptr[0]=='0' && tolower(ptr[1])=='x') {
-		ptr += 2;
-		base = 16;
+	if(__scanf_peek(input) == '0') {
+		__scanf_in(input);
+		if((base == 0 || base == 16) &&
+		   tolower(__scanf_peek(input)) == 'x') {
+			__scanf_in(input);
+			base = 16;
+		}
+		/* If we don't consume the x then count the 0 as a digit */
+		else valid = true;
+		if(base == 0)
+			base = 8;
 	}
-	else if(base == 0 && ptr[0] == '0') {
-		ptr++;
-		base = 8;
-	}
-	else if(base == 0) {
+	if(base == 0)
 		base = 10;
-	}
 
 	/* Read digits */
 	while(1) {
 		int v = -1;
-		if(isdigit(*ptr)) v = *ptr - '0';
-		if(islower(*ptr)) v = *ptr - 'a' + 10;
+		int c = __scanf_peek(input);
+		if(isdigit(c)) v = c - '0';
+		if(islower(c)) v = c - 'a' + 10;
 		if(v == -1 || v >= base) break;
 
 		/* The value is valid as long as there is at least one digit */
 		valid = true;
 
 		/* (x = base*x + v) but with overflow checks */
+		/* TODO: strto_int: We might fail to represent [L]LONG_MIN */
 		if(outl) {
 			if(__builtin_umull_overflow(xl, base, &xl))
 				errno_value = ERANGE;
@@ -62,7 +65,7 @@ int __strto_int(char const * restrict ptr, char ** restrict endptr, int base,
 				errno_value = ERANGE;
 		}
 
-		ptr++;
+		__scanf_in(input);
 	}
 
 	/* Handle sign and range */
@@ -101,6 +104,6 @@ int __strto_int(char const * restrict ptr, char ** restrict endptr, int base,
 
 	if(outl) *outl = xl;
 	if(outll) *outll = xll;
-	if(endptr && valid) *endptr = (char *)ptr;
-	return errno_value;
+
+	return valid ? errno_value : EINVAL;
 }
diff --git a/src/stdlib/strtod.c b/src/stdlib/strtod.c
index 80716fd..130233b 100644
--- a/src/stdlib/strtod.c
+++ b/src/stdlib/strtod.c
@@ -4,7 +4,17 @@
 double strtod(char const * restrict ptr, char ** restrict endptr)
 {
 	double d = 0;
-	int err = __strto_fp(ptr, endptr, &d, NULL, NULL);
-	if(err != 0) errno = err;
+	if(endptr)
+		*endptr = (char *)ptr;
+
+	struct __scanf_input in = { .str = ptr, .fp = NULL };
+	__scanf_start(&in);
+	int err = __strto_fp(&in, &d, NULL, NULL);
+	__scanf_end(&in);
+
+	if(err != 0)
+		errno = err;
+	if(err != EINVAL && endptr)
+		*endptr = (char *)in.str;
 	return d;
 }
diff --git a/src/stdlib/strtof.c b/src/stdlib/strtof.c
index 271aed0..38240ea 100644
--- a/src/stdlib/strtof.c
+++ b/src/stdlib/strtof.c
@@ -4,7 +4,17 @@
 float strtof(char const * restrict ptr, char ** restrict endptr)
 {
 	float f = 0;
-	int err = __strto_fp(ptr, endptr, NULL, &f, NULL);
-	if(err != 0) errno = err;
+	if(endptr)
+		*endptr = (char *)ptr;
+
+	struct __scanf_input in = { .str = ptr, .fp = NULL };
+	__scanf_start(&in);
+	int err = __strto_fp(&in, NULL, &f, NULL);
+	__scanf_end(&in);
+
+	if(err != 0)
+		errno = err;
+	if(err != EINVAL && endptr)
+		*endptr = (char *)in.str;
 	return f;
 }
diff --git a/src/stdlib/strtol.c b/src/stdlib/strtol.c
index b7da918..c0609b3 100644
--- a/src/stdlib/strtol.c
+++ b/src/stdlib/strtol.c
@@ -4,7 +4,17 @@
 long int strtol(char const * restrict ptr, char ** restrict endptr, int base)
 {
 	long n = 0;
-	int err = __strto_int(ptr, endptr, base, &n, NULL, false);
-	if(err != 0) errno = err;
+	if(endptr)
+		*endptr = (char *)ptr;
+
+	struct __scanf_input in = { .str = ptr, .fp = NULL };
+	__scanf_start(&in);
+	int err = __strto_int(&in, base, &n, NULL, false);
+	__scanf_end(&in);
+
+	if(err != 0)
+		errno = err;
+	if(err != EINVAL && endptr)
+		*endptr = (char *)in.str;
 	return n;
 }
diff --git a/src/stdlib/strtold.c b/src/stdlib/strtold.c
index fcb8474..bf6421b 100644
--- a/src/stdlib/strtold.c
+++ b/src/stdlib/strtold.c
@@ -4,7 +4,17 @@
 long double strtold(char const * restrict ptr, char ** restrict endptr)
 {
 	long double ld = 0;
-	int err = __strto_fp(ptr, endptr, NULL, NULL, &ld);
-	if(err != 0) errno = err;
+	if(endptr)
+		*endptr = (char *)ptr;
+
+	struct __scanf_input in = { .str = ptr, .fp = NULL };
+	__scanf_start(&in);
+	int err = __strto_fp(&in, NULL, NULL, &ld);
+	__scanf_end(&in);
+
+	if(err != 0)
+		errno = err;
+	if(err != EINVAL && endptr)
+		*endptr = (char *)in.str;
 	return ld;
 }
diff --git a/src/stdlib/strtoll.c b/src/stdlib/strtoll.c
index ad1c972..2defd3d 100644
--- a/src/stdlib/strtoll.c
+++ b/src/stdlib/strtoll.c
@@ -5,7 +5,17 @@ long long int strtoll(char const * restrict ptr, char ** restrict endptr,
 	int base)
 {
 	long long n = 0;
-	int err = __strto_int(ptr, endptr, base, NULL, &n, false);
-	if(err != 0) errno = err;
+	if(endptr)
+		*endptr = (char *)ptr;
+
+	struct __scanf_input in = { .str = ptr, .fp = NULL };
+	__scanf_start(&in);
+	int err = __strto_int(&in, base, NULL, &n, false);
+	__scanf_end(&in);
+
+	if(err != 0)
+		errno = err;
+	if(err != EINVAL && endptr)
+		*endptr = (char *)in.str;
 	return n;
 }
diff --git a/src/stdlib/strtoul.c b/src/stdlib/strtoul.c
index 2a6294b..a92c265 100644
--- a/src/stdlib/strtoul.c
+++ b/src/stdlib/strtoul.c
@@ -5,7 +5,17 @@ unsigned long int strtoul(char const * restrict ptr, char ** restrict endptr,
 	int base)
 {
 	unsigned long n = 0;
-	int err = __strto_int(ptr, endptr, base, (long *)&n, NULL, true);
-	if(err != 0) errno = err;
+	if(endptr)
+		*endptr = (char *)ptr;
+
+	struct __scanf_input in = { .str = ptr, .fp = NULL };
+	__scanf_start(&in);
+	int err = __strto_int(&in, base, (long *)&n, NULL, true);
+	__scanf_end(&in);
+
+	if(err != 0)
+		errno = err;
+	if(err != EINVAL && endptr)
+		*endptr = (char *)in.str;
 	return n;
 }
diff --git a/src/stdlib/strtoull.c b/src/stdlib/strtoull.c
index d643947..aad4bd3 100644
--- a/src/stdlib/strtoull.c
+++ b/src/stdlib/strtoull.c
@@ -5,7 +5,17 @@ unsigned long long int strtoull(char const * restrict ptr,
 	char ** restrict endptr, int base)
 {
 	unsigned long long n = 0;
-	int err = __strto_int(ptr, endptr, base, NULL, (long long *)&n, true);
-	if(err != 0) errno = err;
+	if(endptr)
+		*endptr = (char *)ptr;
+
+	struct __scanf_input in = { .str = ptr, .fp = NULL };
+	__scanf_start(&in);
+	int err = __strto_int(&in, base, NULL, (long long *)&n, true);
+	__scanf_end(&in);
+
+	if(err != 0)
+		errno = err;
+	if(err != EINVAL && endptr)
+		*endptr = (char *)in.str;
 	return n;
 }