Improve helpers.h

Use C11 standard _Noreturn instead of attributes (except, of course, MSVC)
Remove unused helpers
Avoid trapping in release builds, in favor of just unreachability
Improve shim when __builtin_* are not available

include/asm/warning.h

@@ -55,7 +55,7 @@ void warning(enum WarningID id, const char *fmt, ...);
  * It is also used when the assembler goes into an invalid state (for example,
  * when it fails to allocate memory).
  */
-noreturn_ void fatalerror(const char *fmt, ...);
+_Noreturn void fatalerror(const char *fmt, ...);
 
 /*
  * Used for errors that make it impossible to assemble correctly, but don't

include/extern/err.h

@@ -34,10 +34,10 @@ void vwarn(const char *fmt, va_list ap) format_(printf, 1, 0);
 void warnx(const char *fmt, ...) format_(printf, 1, 2);
 void vwarnx(const char *fmt, va_list ap) format_(printf, 1, 0);
 
-noreturn_ void err(int status, const char *fmt, ...) format_(printf, 2, 3);
+_Noreturn void err(int status, const char *fmt, ...) format_(printf, 2, 3);
-noreturn_ void verr(int status, const char *fmt, va_list ap) format_(printf, 2, 0);
+_Noreturn void verr(int status, const char *fmt, va_list ap) format_(printf, 2, 0);
-noreturn_ void errx(int status, const char *fmt, ...) format_(printf, 2, 3);
+_Noreturn void errx(int status, const char *fmt, ...) format_(printf, 2, 3);
-noreturn_ void verrx(int status, const char *fmt, va_list ap) format_(printf, 2, 0);
+_Noreturn void verrx(int status, const char *fmt, va_list ap) format_(printf, 2, 0);
 
 #endif /* ERR_IN_LIBC */
 

include/helpers.h

@@ -9,21 +9,30 @@
 #ifndef HELPERS_H
 #define HELPERS_H
 
-#ifdef __GNUC__
+// Of course, MSVC does not support C11, so no _Noreturn there...
-	/* GCC or compatible */
+#ifdef _MSC_VER
-	#define format_(archetype, str_index, first_arg) \
+	#define _Noreturn __declspec(noreturn)
-		__attribute__ ((format (archetype, str_index, first_arg)))
-	#define noreturn_	__attribute__ ((noreturn))
-	#define trap_		__builtin_trap()
-#else
-	/* Unsupported, but no need to throw a fit */
-	#define format_(archetype, str_index, first_arg)
-	#define noreturn_
-	#define unused_
-	#define trap_
 #endif
 
-/* Macros for stringification */
+// Ideally, we'd use `__has_attribute` and `__has_builtin`, but these were only introduced in GCC 9
+#ifdef __GNUC__ // GCC or compatible
+	#define format_(archetype, str_index, first_arg) \
+		__attribute__ ((format (archetype, str_index, first_arg)))
+	// In release builds, define "unreachable" as such, but trap in debug builds
+	#ifdef NDEBUG
+		#define unreachable_	__builtin_unreachable
+	#else
+		#define unreachable_	__builtin_trap
+	#endif
+#else
+	// Unsupported, but no need to throw a fit
+	#define format_(archetype, str_index, first_arg)
+	// This seems to generate similar code to __builtin_unreachable, despite different semantics
+	// Note that executing this is undefined behavior (declared _Noreturn, but does return)
+	static inline _Noreturn unreachable_(void) {}
+#endif
+
+// Macros for stringification
 #define STR(x) #x
 #define EXPAND_AND_STR(x) STR(x)
 

include/link/main.h

@@ -66,7 +66,7 @@ void warning(struct FileStackNode const *where, uint32_t lineNo,
 void error(struct FileStackNode const *where, uint32_t lineNo,
 	   char const *fmt, ...) format_(printf, 3, 4);
 
-noreturn_ void fatal(struct FileStackNode const *where, uint32_t lineNo,
+_Noreturn void fatal(struct FileStackNode const *where, uint32_t lineNo,
 		     char const *fmt, ...) format_(printf, 3, 4);
 
 /**

src/asm/warning.c

@@ -222,7 +222,7 @@ void error(const char *fmt, ...)
 	nbErrors++;
 }
 
-noreturn_ void fatalerror(const char *fmt, ...)
+_Noreturn void fatalerror(const char *fmt, ...)
 {
 	va_list args;
 
@@ -250,7 +250,7 @@ void warning(enum WarningID id, char const *fmt, ...)
 		return;
 
 	case WARNING_DEFAULT:
-		trap_;
+		unreachable_();
 		/* Not reached */
 
 	case WARNING_ENABLED:

src/extern/err.c

@@ -34,7 +34,7 @@ void rgbds_vwarnx(const char *fmt, va_list ap)
 	putc('\n', stderr);
 }
 
-noreturn_ void rgbds_verr(int status, const char *fmt, va_list ap)
+_Noreturn void rgbds_verr(int status, const char *fmt, va_list ap)
 {
 	fprintf(stderr, "error: ");
 	if (fmt) {
@@ -46,7 +46,7 @@ noreturn_ void rgbds_verr(int status, const char *fmt, va_list ap)
 	exit(status);
 }
 
-noreturn_ void rgbds_verrx(int status, const char *fmt, va_list ap)
+_Noreturn void rgbds_verrx(int status, const char *fmt, va_list ap)
 {
 	fprintf(stderr, "error");
 	if (fmt) {
@@ -75,7 +75,7 @@ void rgbds_warnx(const char *fmt, ...)
 	va_end(ap);
 }
 
-noreturn_ void rgbds_err(int status, const char *fmt, ...)
+_Noreturn void rgbds_err(int status, const char *fmt, ...)
 {
 	va_list ap;
 
@@ -84,7 +84,7 @@ noreturn_ void rgbds_err(int status, const char *fmt, ...)
 	va_end(ap);
 }
 
-noreturn_ void rgbds_errx(int status, const char *fmt, ...)
+_Noreturn void rgbds_errx(int status, const char *fmt, ...)
 {
 	va_list ap;
 

src/link/assign.c

@@ -439,7 +439,7 @@ void assign_AssignSections(void)
 			return;
 	}
 
-	trap_;
+	unreachable_();
 }
 
 void assign_Cleanup(void)

src/link/main.c

@@ -99,7 +99,7 @@ void error(struct FileStackNode const *where, uint32_t lineNo, char const *fmt,
 		nbErrors++;
 }
 
-noreturn_ void fatal(struct FileStackNode const *where, uint32_t lineNo, char const *fmt, ...)
+_Noreturn void fatal(struct FileStackNode const *where, uint32_t lineNo, char const *fmt, ...)
 {
 	va_list ap;
 

src/link/script.c

@@ -318,7 +318,7 @@ static void processCommand(enum LinkerScriptCommand command, uint16_t arg,
 {
 	switch (command) {
 	case COMMAND_INVALID:
-		trap_;
+		unreachable_();
 
 	case COMMAND_ORG:
 		break;
@@ -391,12 +391,12 @@ struct SectionPlacement *script_NextSection(void)
 
 		switch (parserState) {
 		case PARSER_FIRSTTIME:
-			trap_;
+			unreachable_();
 
 		case PARSER_LINESTART:
 			switch (token->type) {
 			case TOKEN_INVALID:
-				trap_;
+				unreachable_();
 
 			case TOKEN_EOF:
 				if (!popFile())

src/link/section.c

@@ -108,7 +108,7 @@ static void mergeSections(struct Section *target, struct Section *other, enum Se
 		break;
 
 	case SECTION_NORMAL:
-		trap_;
+		unreachable_();
 	}
 
 	other->nextu = target->nextu;