feat(stdlib): numeric string conversions

include/stdlib.h

@@ -105,6 +105,102 @@ __attribute__((pure)) size_t
 malloc_usable_size(void *ptr);
 #endif /* VLIBC_LEVEL_GE(2) */
 
+/* numeric conversions (todo 11) */
+
+/*
+ * String-to-number conversions (C23 7.24.1). All are ISO C core / POSIX
+ * base and present in every profile.
+ *
+ * The ato* wrappers carry no error reporting: their behavior is undefined
+ * if the converted value cannot be represented (C23 7.24.1.1-2), so they
+ * read their input and nothing else — hence pure.
+ *
+ * The strto* functions report range errors through errno and store the
+ * scan position through endptr; both are real side effects, so they carry
+ * no intent attribute. errno behavior follows C23 7.24.1.4-5: ERANGE when
+ * the subject sequence is outside the representable range (the clamped
+ * maximum/minimum is returned); EINVAL when base is not 0 and not in
+ * [2, 36] (endptr left at nptr, 0 returned); endptr points at nptr when
+ * no subject sequence is present.
+ */
+
+/*
+ * Convert the initial decimal digits of nptr to int, discarding leading
+ * whitespace and an optional sign. Equivalent to (int)strtol(nptr, 0, 10).
+ * pure: reads memory, no side effects.
+ */
+__attribute__((pure)) int
+atoi(const char *nptr);
+
+/*
+ * As atoi, converted to long: strtol(nptr, 0, 10).
+ * pure: reads memory, no side effects.
+ */
+__attribute__((pure)) long
+atol(const char *nptr);
+
+/*
+ * As atoi, converted to long long: strtoll(nptr, 0, 10).
+ * pure: reads memory, no side effects.
+ */
+__attribute__((pure)) long long
+atoll(const char *nptr);
+
+/*
+ * As atoi, converted to double: strtod(nptr, 0).
+ * pure: reads memory, no side effects.
+ */
+__attribute__((pure)) double
+atof(const char *nptr);
+
+/*
+ * Convert the initial portion of nptr to long, stopping at the first
+ * character that is not part of the subject sequence and storing its
+ * position in *endptr (if endptr is not NULL). See the family comment for
+ * base, errno, and endptr semantics.
+ */
+long
+strtol(const char *restrict nptr, char **restrict endptr, int base);
+
+/*
+ * As strtol, converted to unsigned long. A subject sequence with a minus
+ * sign yields the negated value computed in the return type (modulo
+ * ULONG_MAX + 1) without a range error (C23 7.24.1.4p8).
+ */
+unsigned long
+strtoul(const char *restrict nptr, char **restrict endptr, int base);
+
+/*
+ * As strtol, converted to long long.
+ */
+long long
+strtoll(const char *restrict nptr, char **restrict endptr, int base);
+
+/*
+ * As strtol, converted to unsigned long long. Negative subject sequences
+ * wrap modulo ULLONG_MAX + 1 as for strtoul.
+ */
+unsigned long long
+strtoull(const char *restrict nptr, char **restrict endptr, int base);
+
+/*
+ * Convert the initial portion of nptr to float, double, or long double
+ * (C23 7.24.1.3): optional whitespace, optional sign, then either an
+ * "inf"/"infinity" or "nan"/"nan(n-char-sequence)" subject (case-
+ * insensitive), a hexadecimal floating subject ("0x1.8p1"), or a decimal
+ * floating subject with optional exponent. Overflow returns ±HUGE_VAL*
+ * with errno ERANGE; results too small to represent return a subnormal or
+ * zero value with errno ERANGE. no-conversion stores nptr in *endptr.
+ */
+double
+strtod(const char *restrict nptr, char **restrict endptr);
+
+float
+strtof(const char *restrict nptr, char **restrict endptr);
+
+long double
+strtold(const char *restrict nptr, char **restrict endptr);
+
 #ifdef __cplusplus
 }
 #endif