Add support for C23 attribute syntax

Currently, all attributes are ignored.

References: https://todo.sr.ht/~mcf/cproc/68

1 files changed, 90 insertions, 0 deletions

diff --git a/attr.c b/attr.c
new file mode 100644
index 0000000..75ec5ef
--- /dev/null
+++ b/attr.c
@@ -0,0 +1,90 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+#include "util.h"
+#include "cc.h"
+
+enum attrprefix {
+	PREFIXNONE = 1,  /* standard attribute */
+	PREFIXGNU,
+};
+
+static char *
+strip(char *name)
+{
+	size_t len;
+
+	len = strlen(name);
+	if (len >= 4 && name[0] == '_' && name[1] == '_' && name[len - 2] == '_' && name[len - 1] == '_') {
+		name[len - 2] = '\0';
+		name += 2;
+	}
+	return name;
+}
+
+static bool
+parseattr(struct attr *a, enum attrkind allowed, enum attrprefix prefix)
+{
+	char *name, *prefixname = "";
+	enum attrkind kind;
+	int paren;
+
+	if (tok.kind != TIDENT)
+		return false;
+	name = strip(tok.lit);
+	next();
+	if (!prefix) {
+		if (consume(TCOLONCOLON)) {
+			if (strcmp(name, "gnu") == 0)
+				prefix = PREFIXGNU;
+			else
+				prefix = 0;
+			name = strip(expect(TIDENT, "after attribute prefix"));
+		} else {
+			prefix = PREFIXNONE;
+		}
+	}
+	kind = 0;
+	switch (prefix) {
+	case PREFIXGNU:
+		prefixname = "GNU ";
+		break;
+	}
+	if (kind) {
+		if (!(kind & allowed))
+			error(&tok.loc, "%sattribute '%s' is not supported here", prefixname, name);
+		if (a)
+			a->kind |= kind;
+	} else if (consume(TLPAREN)) {
+		/* skip arguments */
+		for (paren = 1; paren > 0; next()) {
+			switch (tok.kind) {
+			case TLPAREN: ++paren; break;
+			case TRPAREN: --paren; break;
+			}
+		}
+	}
+	return true;
+}
+
+static bool
+attrspec(struct attr *a, enum attrkind allowed)
+{
+	if (tok.kind != TLBRACK || !peek(TLBRACK))
+		return false;
+	while (parseattr(a, allowed, 0) || consume(TCOMMA))
+		;
+	expect(TRBRACK, "to end attribute specifier");
+	expect(TRBRACK, "to end attribute specifier");
+	return true;
+}
+
+bool
+attr(struct attr *a, enum attrkind allowed)
+{
+	if (!attrspec(a, allowed))
+		return false;
+	while (attrspec(a, allowed))
+		;
+	return true;
+}