From ad5da0c9246337e23b22afa1ee8f5f8c2be4a048 Mon Sep 17 00:00:00 2001
From: Peter Nelson <peter1138@openttd.org>
Date: Thu, 12 Sep 2024 07:06:15 +0100
Subject: [PATCH] Codechange: Use `__VA_OPT__(,)` instead of `, ##` (#12921)

`__VA_OPT__` is a C++20 standard, `##` is, apparently, a GNU extension.

MSVC needs /Zc:preprocessor adding for whatever reason.
---
 cmake/CompileFlags.cmake | 3 +++
 src/debug.h              | 4 ++--
 src/error_func.h         | 4 ++--
 src/newgrf.h             | 2 +-
 src/strgen/strgen.h      | 6 +++---
 5 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/cmake/CompileFlags.cmake b/cmake/CompileFlags.cmake
index 8da4be8bab..073c01c2fd 100644
--- a/cmake/CompileFlags.cmake
+++ b/cmake/CompileFlags.cmake
@@ -8,6 +8,9 @@ macro(compile_flags)
         # C++11 standard". We need C++11 for the way we use threads.
         add_compile_options(/Zc:rvalueCast)
 
+        # Needed for __VA_OPT__() in macros.
+        add_compile_options(/Zc:preprocessor)
+
         if(NOT CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
             add_compile_options(
                 /MP # Enable multi-threaded compilation.
diff --git a/src/debug.h b/src/debug.h
index c5afb9180a..d9ac37207e 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -34,7 +34,7 @@
  * @param level The maximum debug level this message should be shown at. When the debug level for this category is set lower, then the message will not be shown.
  * @param format_string The formatting string of the message.
  */
-#define Debug(category, level, format_string, ...) do { if ((level) == 0 || _debug_ ## category ## _level >= (level)) DebugPrint(#category, level, fmt::format(FMT_STRING(format_string), ## __VA_ARGS__)); } while (false)
+#define Debug(category, level, format_string, ...) do { if ((level) == 0 || _debug_ ## category ## _level >= (level)) DebugPrint(#category, level, fmt::format(FMT_STRING(format_string) __VA_OPT__(,) __VA_ARGS__)); } while (false)
 void DebugPrint(const char *category, int level, const std::string &message);
 
 extern int _debug_driver_level;
@@ -93,7 +93,7 @@ struct TicToc {
 };
 
 void ShowInfoI(const std::string &str);
-#define ShowInfo(format_string, ...) ShowInfoI(fmt::format(FMT_STRING(format_string), ## __VA_ARGS__))
+#define ShowInfo(format_string, ...) ShowInfoI(fmt::format(FMT_STRING(format_string) __VA_OPT__(,) __VA_ARGS__))
 
 std::string GetLogPrefix(bool force = false);
 
diff --git a/src/error_func.h b/src/error_func.h
index afbe763abe..0f5c9c1d66 100644
--- a/src/error_func.h
+++ b/src/error_func.h
@@ -14,7 +14,7 @@
 
 [[noreturn]] void UserErrorI(const std::string &str);
 [[noreturn]] void FatalErrorI(const std::string &str);
-#define UserError(format_string, ...) UserErrorI(fmt::format(FMT_STRING(format_string), ## __VA_ARGS__))
-#define FatalError(format_string, ...) FatalErrorI(fmt::format(FMT_STRING(format_string), ## __VA_ARGS__))
+#define UserError(format_string, ...) UserErrorI(fmt::format(FMT_STRING(format_string) __VA_OPT__(,) __VA_ARGS__))
+#define FatalError(format_string, ...) FatalErrorI(fmt::format(FMT_STRING(format_string) __VA_OPT__(,) __VA_ARGS__))
 
 #endif /* ERROR_FUNC_H */
diff --git a/src/newgrf.h b/src/newgrf.h
index e49c22ee5c..b08376dc57 100644
--- a/src/newgrf.h
+++ b/src/newgrf.h
@@ -202,7 +202,7 @@ void ResetNewGRFData();
 void ResetPersistentNewGRFData();
 
 void GrfMsgI(int severity, const std::string &msg);
-#define GrfMsg(severity, format_string, ...) do { if ((severity) == 0 || _debug_grf_level >= (severity)) GrfMsgI(severity, fmt::format(FMT_STRING(format_string), ## __VA_ARGS__)); } while (false)
+#define GrfMsg(severity, format_string, ...) do { if ((severity) == 0 || _debug_grf_level >= (severity)) GrfMsgI(severity, fmt::format(FMT_STRING(format_string) __VA_OPT__(,) __VA_ARGS__)); } while (false)
 
 bool GetGlobalVariable(uint8_t param, uint32_t *value, const GRFFile *grffile);
 
diff --git a/src/strgen/strgen.h b/src/strgen/strgen.h
index 99594b2019..3cd83c05cb 100644
--- a/src/strgen/strgen.h
+++ b/src/strgen/strgen.h
@@ -150,9 +150,9 @@ ParsedCommandStruct ExtractCommandString(const char *s, bool warnings);
 void StrgenWarningI(const std::string &msg);
 void StrgenErrorI(const std::string &msg);
 [[noreturn]] void StrgenFatalI(const std::string &msg);
-#define StrgenWarning(format_string, ...) StrgenWarningI(fmt::format(FMT_STRING(format_string), ## __VA_ARGS__))
-#define StrgenError(format_string, ...) StrgenErrorI(fmt::format(FMT_STRING(format_string), ## __VA_ARGS__))
-#define StrgenFatal(format_string, ...) StrgenFatalI(fmt::format(FMT_STRING(format_string), ## __VA_ARGS__))
+#define StrgenWarning(format_string, ...) StrgenWarningI(fmt::format(FMT_STRING(format_string) __VA_OPT__(,) __VA_ARGS__))
+#define StrgenError(format_string, ...) StrgenErrorI(fmt::format(FMT_STRING(format_string) __VA_OPT__(,) __VA_ARGS__))
+#define StrgenFatal(format_string, ...) StrgenFatalI(fmt::format(FMT_STRING(format_string) __VA_OPT__(,) __VA_ARGS__))
 char *ParseWord(char **buf);
 
 extern const char *_file;