From d5ce5329ea3ac8255d1cc1fa30c260bc0d534b77 Mon Sep 17 00:00:00 2001
From: ISSOtm <me@eldred.fr>
Date: Sun, 26 Apr 2026 14:46:11 +0200
Subject: [PATCH] Fix compilation with GCC 9

---
 Makefile             | 3 ++-
 include/util.hpp     | 4 ++--
 src/asm/fixpoint.cpp | 4 ++--
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index 8f7f1ad9..81078c29 100644
--- a/Makefile
+++ b/Makefile
@@ -31,7 +31,8 @@ WARNFLAGS := -Wall -pedantic -Wno-unknown-warning-option -Wno-gnu-zero-variadic-
 # Overridable CXXFLAGS
 CXXFLAGS     ?= -O3 -flto -DNDEBUG
 # Non-overridable CXXFLAGS
-REALCXXFLAGS := ${CXXFLAGS} ${WARNFLAGS} -std=c++20 -I include -fno-exceptions -fno-rtti
+# GCC 9 doesn't support `-std=c++20`, and all later GCCs treat it as equivalent to `-std=c++2a`.
+REALCXXFLAGS := ${CXXFLAGS} ${WARNFLAGS} -std=c++2a -I include -fno-exceptions -fno-rtti
 # Overridable LDFLAGS
 LDFLAGS      ?=
 # Non-overridable LDFLAGS
diff --git a/include/util.hpp b/include/util.hpp
index 3d8b208a..7d025448 100644
--- a/include/util.hpp
+++ b/include/util.hpp
@@ -50,14 +50,14 @@ char const *printChar(int c);
 
 struct Uppercase {
 	// FNV-1a hash of an uppercased string
-	constexpr size_t operator()(std::string const &str) const {
+	size_t operator()(std::string const &str) const {
 		return std::accumulate(RANGE(str), size_t(0x811C9DC5), [](size_t hash, char c) {
 			return (hash ^ toUpper(c)) * 16777619;
 		});
 	}
 
 	// Compare two strings without case-sensitivity (by converting to uppercase)
-	constexpr bool operator()(std::string const &str1, std::string const &str2) const {
+	bool operator()(std::string const &str1, std::string const &str2) const {
 		return std::equal(RANGE(str1), RANGE(str2), [](char c1, char c2) {
 			return toUpper(c1) == toUpper(c2);
 		});
diff --git a/src/asm/fixpoint.cpp b/src/asm/fixpoint.cpp
index d8097bac..c492eba3 100644
--- a/src/asm/fixpoint.cpp
+++ b/src/asm/fixpoint.cpp
@@ -5,10 +5,10 @@
 #include "asm/fixpoint.hpp"
 
 #include <math.h>
-#include <numbers>
 #include <stdint.h>
 
-static constexpr double tau = std::numbers::pi * 2;
+// Ideally we'd use `std::numbers::pi`, but GCC 9 doesn't support it.
+static constexpr double tau = 3.141592653589793238462643383279502884L * 2;
 
 static double fix2double(int32_t i, int32_t q) {
 	return i / pow(2.0, q);