decl: Support variadic functions with no other parameters

8 files changed, 63 insertions, 18 deletions

diff --git a/decl.c b/decl.c
index 96428ba..a9ee504 100644
--- a/decl.c
+++ b/decl.c
@@ -604,20 +604,21 @@ declaratortypes(struct scope *s, struct list *result, char **name, struct scope
 			t->u.func.nparam = 0;
 			paramend = &t->u.func.params;
 			s = mkscope(s);
-			while (tok.kind != TRPAREN) {
+			do {
+				if (consume(TELLIPSIS)) {
+					t->u.func.isvararg = true;
+					break;
+				}
+				if (tok.kind == TRPAREN)
+					break;
 				d = parameter(s);
 				if (d->name)
 					scopeputdecl(s, d);
 				*paramend = d;
 				paramend = &d->next;
 				++t->u.func.nparam;
-				if (!consume(TCOMMA))
-					break;
-				if (consume(TELLIPSIS)) {
-					t->u.func.isvararg = true;
-					break;
-				}
-			}
+			} while (consume(TCOMMA));
+			expect(TRPAREN, "to close function declarator");
 			if (funcscope && ptr->prev == prev) {
 				/* we may need to re-open the scope later if this is a function definition */
 				*funcscope = s;
@@ -629,7 +630,6 @@ declaratortypes(struct scope *s, struct list *result, char **name, struct scope
 				t->u.func.params = NULL;
 				t->u.func.nparam = 0;
 			}
-			expect(TRPAREN, "to close function declarator");
 			listinsert(ptr->prev, &t->link);
 			allowattr = true;
 			break;
diff --git a/doc/c23.md b/doc/c23.md
index 1c555b4..a8a50e3 100644
--- a/doc/c23.md
+++ b/doc/c23.md
@@ -50,6 +50,12 @@ with `typeof` to specify that same type.
 C23 also introduces `typeof_unqual`, which behaves the same as
 `typeof` except that the specified type is unqualified.
 
+## [N2975]: Relax requirements for variadic parameter lists
+
+C23 allows variadic functions with no named parameters. The second
+argument to the va_arg macro is now optional and is only used for
+backwards compatibility.
+
 ## [N3029]: Improved Normal Enumerations
 
 C23 allows enumerators outside the range of `int`. When an enum
@@ -79,5 +85,6 @@ used inside the enum.
 [N2549]: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2549.pdf
 [N2900]: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2900.htm
 [N2927]: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2927.htm
+[N2975]: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2975.pdf
 [N3029]: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3029.htm
 [N3030]: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3030.htm
diff --git a/expr.c b/expr.c
index 22fd242..fb6c144 100644
--- a/expr.c
+++ b/expr.c
@@ -773,7 +773,7 @@ designator(struct scope *s, struct type *t, unsigned long long *offset)
 static struct expr *
 builtinfunc(struct scope *s, enum builtinkind kind)
 {
-	struct expr *e, *param;
+	struct expr *e;
 	struct type *t;
 	struct member *m;
 	char *name;
@@ -868,12 +868,8 @@ builtinfunc(struct scope *s, enum builtinkind kind)
 			error(&tok.loc, "va_start argument must have type va_list");
 		if (typeadjvalist == targ->typevalist)
 			e->base = mkunaryexpr(TBAND, e->base);
-		expect(TCOMMA, "after va_list");
-		param = assignexpr(s);
-		if (param->kind != EXPRIDENT)
-			error(&tok.loc, "expected parameter identifier");
-		delexpr(param);
-		/* XXX: check that this was actually a parameter name? */
+		if (consume(TCOMMA))
+			delexpr(assignexpr(s));
 		break;
 	default:
 		fatal("internal error; unknown builtin");
diff --git a/qbe.c b/qbe.c
index 13643dc..e98e6fe 100644
--- a/qbe.c
+++ b/qbe.c
@@ -1219,8 +1219,11 @@ emitfunc(struct func *f, bool global)
 		putchar(' ');
 		emitvalue(v);
 	}
-	if (f->type->u.func.isvararg)
-		fputs(", ...", stdout);
+	if (f->type->u.func.isvararg) {
+		if (f->type->u.func.params)
+			fputs(", ", stdout);
+		fputs("...", stdout);
+	}
 	puts(") {");
 	for (b = f->start; b; b = b->next) {
 		emitvalue(&b->label);
diff --git a/test/varargs+aarch64.qbe b/test/varargs+aarch64.qbe
index 5b6e830..c444c85 100644
--- a/test/varargs+aarch64.qbe
+++ b/test/varargs+aarch64.qbe
@@ -45,3 +45,13 @@ function $f3(w %.1, ...) {
 @while_join.9
 	ret
 }
+export
+function $f4(...) {
+@start.10
+	%.1 =l alloc8 32
+@body.11
+	vastart %.1
+	%.2 =d vaarg %.1
+	%.3 =w vaarg %.1
+	ret
+}
diff --git a/test/varargs+riscv64.qbe b/test/varargs+riscv64.qbe
index 48638bb..1b0851e 100644
--- a/test/varargs+riscv64.qbe
+++ b/test/varargs+riscv64.qbe
@@ -49,3 +49,14 @@ function $f3(w %.1, ...) {
 	%.10 =l loadl %.3
 	ret
 }
+export
+function $f4(...) {
+@start.10
+	%.1 =l alloc8 8
+@body.11
+	vastart %.1
+	%.2 =d vaarg %.1
+	%.3 =w vaarg %.1
+	%.4 =l loadl %.1
+	ret
+}
diff --git a/test/varargs+x86_64-sysv.c b/test/varargs+x86_64-sysv.c
index 71bf1d3..dfa1b98 100644
--- a/test/varargs+x86_64-sysv.c
+++ b/test/varargs+x86_64-sysv.c
@@ -24,3 +24,11 @@ void f3(int n, ...) {
 	}
 	__builtin_va_end(ap);
 }
+
+void f4(...) {
+	__builtin_va_list ap;
+	__builtin_va_start(ap);
+	__builtin_va_arg(ap, double);
+	__builtin_va_arg(ap, int);
+	__builtin_va_end(ap);
+}
diff --git a/test/varargs+x86_64-sysv.qbe b/test/varargs+x86_64-sysv.qbe
index 46904b6..4fa8e7b 100644
--- a/test/varargs+x86_64-sysv.qbe
+++ b/test/varargs+x86_64-sysv.qbe
@@ -47,3 +47,13 @@ function $f3(w %.1, ...) {
 @while_join.9
 	ret
 }
+export
+function $f4(...) {
+@start.10
+	%.1 =l alloc8 24
+@body.11
+	vastart %.1
+	%.2 =d vaarg %.1
+	%.3 =w vaarg %.1
+	ret
+}