Use some more C++20 features (#1231)

src/fix/main.cpp

@@ -1197,7 +1197,7 @@ static bool processFilename(char const *name)
 
 		if (fstat(input, &stat) == -1) {
 			report("FATAL: Failed to stat \"%s\": %s\n", name, strerror(errno));
-		} else if (!S_ISREG(stat.st_mode)) { // FIXME: Do we want to support other types?
+		} else if (!S_ISREG(stat.st_mode)) { // TODO: Do we want to support other types?
 			report("FATAL: \"%s\" is not a regular file, and thus cannot be modified in-place\n",
 				name);
 		} else if (stat.st_size < 0x150) {

src/gfx/pal_spec.cpp

@@ -4,6 +4,7 @@
 
 #include <algorithm>
 #include <cassert>
+#include <charconv>
 #include <cinttypes>
 #include <climits>
 #include <cstdint>
@@ -218,21 +219,18 @@ static void readLine(std::filebuf &file, std::string &buffer) {
 	}
 }
 
-// FIXME: Normally we'd use `std::from_chars`, but that's not available with GCC 7
 /*
  * Parses the initial part of a string_view, advancing the "read index" as it does
  */
 template<typename U> // Should be uint*_t
 static std::optional<U> parseDec(std::string const &str, std::string::size_type &n) {
-	std::string::size_type start = n;
+	uintmax_t value = 0;
-
+	auto result = std::from_chars(str.data(), str.data() + str.size(), value);
-	uintmax_t value = 0; // Use a larger type to handle overflow more easily
+	if ((bool)result.ec) {
-	for (auto end = std::min(str.length(), str.find_first_not_of("0123456789"sv, n)); n < end;
+		return std::nullopt;
-	     ++n) {
-		value = std::min(value * 10 + (str[n] - '0'), (uintmax_t)std::numeric_limits<U>::max);
 	}
-
+	n += result.ptr - str.data();
-	return n > start ? std::optional<U>{value} : std::nullopt;
+	return std::optional<U>{value};
 }
 
 static std::optional<Rgba> parseColor(std::string const &str, std::string::size_type &n,
@@ -334,8 +332,7 @@ static void parseGPLFile(std::filebuf &file) {
 
 	std::string line;
 	readLine(file, line);
-	// FIXME: C++20 will allow `!line.starts_with` instead of `line.rfind` with 0
+	if (!line.starts_with("GIMP Palette")) {
-	if (line.rfind("GIMP Palette", 0)) {
 		error("Palette file does not appear to be a GPL palette file");
 		return;
 	}
@@ -350,8 +347,7 @@ static void parseGPLFile(std::filebuf &file) {
 			break;
 		}
 
-		// FIXME: C++20 will allow `line.starts_with` instead of `!line.rfind` with 0
+		if (line.starts_with("#") || line.starts_with("Name:") || line.starts_with("Column:")) {
-		if (!line.rfind("#", 0) || !line.rfind("Name:", 0) || !line.rfind("Column:", 0)) {
 			continue;
 		}
 

src/link/main.cpp

@@ -402,7 +402,7 @@ int main(int argc, char *argv[])
 			parseScrambleSpec(musl_optarg);
 			break;
 		case 's':
-			// FIXME: nobody knows what this does, figure it out
+			// TODO: implement "smart linking" with `-s`
 			(void)musl_optarg;
 			warning(NULL, 0, "Nobody has any idea what `-s` does");
 			break;

src/link/output.cpp

@@ -330,8 +330,8 @@ static int compareSymbols(void const *a, void const *b)
 
 	char const *sym1_name = sym1->sym->name;
 	char const *sym2_name = sym2->sym->name;
-	bool sym1_local = !!strchr(sym1_name, '.');
+	bool sym1_local = strchr(sym1_name, '.');
-	bool sym2_local = !!strchr(sym2_name, '.');
+	bool sym2_local = strchr(sym2_name, '.');
 
 	if (sym1_local != sym2_local) {
 		size_t sym1_len = strlen(sym1_name);