Remove use of std::from_chars and <charconv>

Replace it with another implementation to avoid compilation issues
on some platforms

src/fios.cpp

@@ -17,12 +17,12 @@
 #include "network/network_content.h"
 #include "screenshot.h"
 #include "string_func.h"
+#include "string_func_extra.h"
 #include "strings_func.h"
 #include "tar_type.h"
 #include <sys/stat.h>
 #include <functional>
 #include "3rdparty/optional/ottd_optional.h"
-#include <charconv>
 
 #ifndef _WIN32
 # include <unistd.h>
@@ -780,7 +780,7 @@ FiosNumberedSaveName::FiosNumberedSaveName(const std::string &prefix) : prefix(p
 		_savegame_sort_order = order;
 
 		std::string_view name = list.begin()->title;
-		std::from_chars(name.data() + this->prefix.size(), name.data() + name.size(), this->number);
+		IntFromChars(name.data() + this->prefix.size(), name.data() + name.size(), this->number);
 	}
 }
 

src/network/network.cpp

@@ -36,7 +36,7 @@
 #include "../gfx_func.h"
 #include "../error.h"
 #include "../core/checksum_func.hpp"
-#include <charconv>
+#include "../string_func_extra.h"
 #include <sstream>
 #include <iomanip>
 
@@ -496,8 +496,8 @@ std::string_view ParseCompanyFromConnectionString(const std::string &connection_
 		ip = ip.substr(0, offset);
 
 		uint8 company_value;
-		auto [_, err] = std::from_chars(company_string.data(), company_string.data() + company_string.size(), company_value);
+		bool success = IntFromChars(company_string.data(), company_string.data() + company_string.size(), company_value);
-		if (err == std::errc()) {
+		if (success) {
 			if (company_value != COMPANY_NEW_COMPANY && company_value != COMPANY_SPECTATOR) {
 				if (company_value > MAX_COMPANIES || company_value == 0) {
 					*company_id = COMPANY_SPECTATOR;
@@ -538,7 +538,7 @@ std::string_view ParseFullConnectionString(const std::string &connection_string,
 	if (port_offset != std::string::npos && (ipv6_close == std::string::npos || ipv6_close < port_offset)) {
 		std::string_view port_string = ip.substr(port_offset + 1);
 		ip = ip.substr(0, port_offset);
-		std::from_chars(port_string.data(), port_string.data() + port_string.size(), port);
+		IntFromChars(port_string.data(), port_string.data() + port_string.size(), port);
 	}
 	return ip;
 }

src/settings.cpp

@@ -23,7 +23,6 @@
 
 #include "stdafx.h"
 #include <array>
-#include <charconv>
 #include <limits>
 #include "currency.h"
 #include "screenshot.h"
@@ -77,6 +76,7 @@
 #include "gui.h"
 #include "statusbar_gui.h"
 #include "graph_gui.h"
+#include "string_func_extra.h"
 
 #include "void_map.h"
 #include "station_base.h"
@@ -1982,7 +1982,7 @@ static IniFileVersion LoadVersionFromConfig(IniFile &ini)
 	if (version_number == nullptr || !version_number->value.has_value()) return IFV_0;
 
 	uint32 version = 0;
-	std::from_chars(version_number->value->data(), version_number->value->data() + version_number->value->size(), version);
+	IntFromChars(version_number->value->data(), version_number->value->data() + version_number->value->size(), version);
 
 	return static_cast<IniFileVersion>(version);
 }

src/string_func_extra.h

@@ -10,6 +10,7 @@
 
 #include "string_func.h"
 #include <string>
+#include <limits>
 
 static inline void StrMakeValidInPlace(std::string &str, StringValidationSettings settings = SVS_REPLACE_WITH_QUESTION_MARK)
 {
@@ -34,5 +35,45 @@ inline void ProcessLineByLine(char *buf, F line_functor)
 	if (p < p2) line_functor(p);
 }
 
+/*
+ * Cut down version of std::from_chars, base is fixed at 10.
+ * Returns true on success
+ */
+template <typename T>
+inline bool IntFromChars(const char* first, const char* last, T& value)
+{
+	static_assert(std::is_integral<T>::value && !std::is_same<T, bool>::value, "T must be an integer");
+
+	bool negative = false;
+	if (std::is_signed<T>::value) {
+		if (first != last && *first == '-') {
+			first++;
+			negative = true;
+		}
+	}
+
+	T out = 0;
+	const char * const start = first;
+	while (first != last) {
+		const char c = *first;
+		if (c >= '0' && c <= '9') {
+#ifdef WITH_OVERFLOW_BUILTINS
+			if (unlikely(__builtin_mul_overflow(out, 10, &out))) return false;
+			if (unlikely(__builtin_add_overflow(out, c - '0', &out))) return false;
+#else
+			if (unlikely(out > std::numeric_limits<T>::max() / 10)) return false;
+			out *= 10;
+			if (unlikely(out > (std::numeric_limits<T>::max() - (c - '0')))) return false;
+			out += (c - '0');
+#endif
+			first++;
+		} else {
+			break;
+		}
+	}
+	if (start == first) return false;
+	value = negative ? -out : out;
+	return true;
+}
 
 #endif /* STRING_FUNC_EXTRA_H */