fix warnings and add to modulemap

Author: michaelrj-google

libcxx/include/module.modulemap

@@ -1075,18 +1075,19 @@ module std_private_bit_invert_if      [system] { header "__bit/invert_if.h" }
 module std_private_bit_popcount       [system] { header "__bit/popcount.h" }
 module std_private_bit_rotate         [system] { header "__bit/rotate.h" }
 
-module std_private_charconv_chars_format            [system] { header "__charconv/chars_format.h" }
-module std_private_charconv_from_chars_integral     [system] { header "__charconv/from_chars_integral.h" }
-module std_private_charconv_from_chars_result       [system] { header "__charconv/from_chars_result.h" }
-module std_private_charconv_tables                  [system] { header "__charconv/tables.h" }
-module std_private_charconv_to_chars                [system] { header "__charconv/to_chars.h" }
-module std_private_charconv_to_chars_base_10        [system] { header "__charconv/to_chars_base_10.h" }
-module std_private_charconv_to_chars_floating_point [system] { header "__charconv/to_chars_floating_point.h" }
-module std_private_charconv_to_chars_integral       [system] {
+module std_private_charconv_chars_format              [system] { header "__charconv/chars_format.h" }
+module std_private_charconv_from_chars_integral       [system] { header "__charconv/from_chars_integral.h" }
+module std_private_charconv_from_chars_result         [system] { header "__charconv/from_chars_result.h" }
+module std_private_charconv_tables                    [system] { header "__charconv/tables.h" }
+module std_private_charconv_to_chars                  [system] { header "__charconv/to_chars.h" }
+module std_private_charconv_to_chars_base_10          [system] { header "__charconv/to_chars_base_10.h" }
+module std_private_charconv_to_chars_floating_point   [system] { header "__charconv/to_chars_floating_point.h" }
+module std_private_charconv_from_chars_floating_point [system] { header "__charconv/from_chars_floating_point.h" }
+module std_private_charconv_to_chars_integral         [system] {
   header "__charconv/to_chars_integral.h"
   export std_private_charconv_traits
 }
-module std_private_charconv_to_chars_result         [system] {
+module std_private_charconv_to_chars_result           [system] {
   header "__charconv/to_chars_result.h"
   export *
 }

libcxx/src/include/from_chars_floating_point.h

@@ -51,7 +51,7 @@ from_chars_result from_chars_floating_point(const char* __first, const char* __l
 
   // The loop fills the mantissa with as many digits as it can hold
   const _Uint_type bitstype_max_div_by_base = numeric_limits<_Uint_type>::max() / BASE;
-  while (index < length) {
+  while (index < static_cast<size_t>(length)) {
     if (LIBC_NAMESPACE::internal::isdigit(src[index])) {
       uint32_t digit = src[index] - '0';
       seen_digit     = true;
@@ -86,12 +86,12 @@ from_chars_result from_chars_floating_point(const char* __first, const char* __l
   if (!seen_digit)
     return {src + index, {}};
 
-  if (index < length && LIBC_NAMESPACE::internal::tolower(src[index]) == EXPONENT_MARKER) {
+  if (index < static_cast<size_t>(length) && LIBC_NAMESPACE::internal::tolower(src[index]) == EXPONENT_MARKER) {
     bool has_sign = false;
-    if (index + 1 < length && (src[index + 1] == '+' || src[index + 1] == '-')) {
+    if (index + 1 < static_cast<size_t>(length) && (src[index + 1] == '+' || src[index + 1] == '-')) {
       has_sign = true;
     }
-    if (index + 1 + static_cast<size_t>(has_sign) < length &&
+    if (index + 1 + static_cast<size_t>(has_sign) < static_cast<size_t>(length) &&
         LIBC_NAMESPACE::internal::isdigit(src[index + 1 + static_cast<size_t>(has_sign)])) {
       ++index;
       auto result = LIBC_NAMESPACE::internal::strtointeger<int32_t>(src + index, 10);