From 591853a8ddd01258a5dbf9484a3fd2114e5e87e7 Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Sun, 24 Mar 2024 00:06:47 -0700
Subject: attr: Add support for GNU syntax

References: https://todo.sr.ht/~mcf/cproc/68
---
 attr.c | 26 ++++++++++++++++++++++++++
 cc.h   |  1 +
 decl.c |  7 ++++++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/attr.c b/attr.c
index 75ec5ef..8b06d46 100644
--- a/attr.c
+++ b/attr.c
@@ -88,3 +88,29 @@ attr(struct attr *a, enum attrkind allowed)
 		;
 	return true;
 }
+
+static bool
+gnuattrspec(struct attr *a, enum attrkind allowed)
+{
+	if (!consume(T__ATTRIBUTE__))
+		return false;
+	while (parseattr(a, allowed, PREFIXGNU) || consume(TCOMMA))
+		;
+	expect(TLPAREN, "after '__attribute__' to begin attribute specifier");
+	expect(TLPAREN, "after '__attribute__' to begin attribute specifier");
+	while (parseattr(a, allowed, PREFIXGNU) || consume(TCOMMA))
+		;
+	expect(TRPAREN, "to end attribute specifier");
+	expect(TRPAREN, "to end attribute specifier");
+	return true;
+}
+
+bool
+gnuattr(struct attr *a, enum attrkind allowed)
+{
+	if (!gnuattrspec(a, allowed))
+		return false;
+	while (gnuattrspec(a, allowed))
+		;
+	return true;
+}
diff --git a/cc.h b/cc.h
index 2bf61c3..e07273f 100644
--- a/cc.h
+++ b/cc.h
@@ -481,6 +481,7 @@ struct attr {
 };
 
 _Bool attr(struct attr *, enum attrkind);
+_Bool gnuattr(struct attr *, enum attrkind);
 
 /* decl */
 
diff --git a/decl.c b/decl.c
index 6e0ee37..98ac497 100644
--- a/decl.c
+++ b/decl.c
@@ -171,6 +171,7 @@ tagspec(struct scope *s)
 	}
 	next();
 	attr(NULL, 0);
+	gnuattr(NULL, 0);
 	tag = NULL;
 	t = NULL;
 	et = NULL;
@@ -452,6 +453,10 @@ declspecs(struct scope *s, enum storageclass *sc, enum funcspec *fs, int *align)
 			expect(TRPAREN, "to close 'alignas' specifier");
 			break;
 
+		case T__ATTRIBUTE__:
+			gnuattr(NULL, 0);
+			break;
+
 		default:
 			goto done;
 		}
@@ -660,7 +665,7 @@ declaratortypes(struct scope *s, struct list *result, char **name, bool allowabs
 			if (!allowattr)
 				error(&tok.loc, "attribute not allowed after parenthesized declarator");
 			/* attribute applies to identifier if ptr->prev == result, otherwise type ptr->prev */
-			attr(NULL, 0);
+			gnuattr(NULL, 0);
 		attr:
 			break;
 		default:
-- 
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