backend: Add abstract syntax tree groundwork

Signed-off-by: Ian Moffett <ian@mirocom.org>

backend/ast.c

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2026, Mirocom Laboratories
+ * Provided under the BSD-3 clause
+ *
+ * Abstract:
+ *      This file implements abstract syntaxt tree creation
+ *      logic.
+ * Author:
+ *      Ian M. Moffett <ian@mirocom.org>
+ */
+
+#include <stddef.h>
+#include <errno.h>
+#include <stdlib.h>
+#include "backend/ast.h"
+
+int
+ast_node_alloc(struct quip_state *state, ast_type_t type, struct ast_node **res)
+{
+    struct ast_node *node;
+
+    if (res == NULL) {
+        errno = -EINVAL;
+        return -1;
+    }
+
+    node = ptrbox_malloc(&state->ptrbox, (sizeof(*node)));
+    if (node == NULL) {
+        errno = -ENOMEM;
+        return -1;
+    }
+
+    node->left = NULL;
+    node->right = NULL;
+    node->data = NULL;
+    *res = node;
+    return 0;
+}

include/backend/ast.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2026, Mirocom Laboratories
+ * Provided under the BSD-3 clause
+ *
+ * Abstract:
+ *      This file provides abstract syntax tree related
+ *      definitions.
+ * Author:
+ *      Ian M. Moffett <ian@mirocom.org>
+ */
+
+#ifndef BACKEND_AST_H
+#define BACKEND_AST_H 1
+
+#include <stdint.h>
+#include <stddef.h>
+#include "common/state.h"
+
+/*
+ * Represents an abstract syntax tree
+ *
+ * @AST_TYPE_NONE:  This node has node associated type
+ */
+typedef enum {
+    AST_TYPE_NONE,
+    AST_TYPE_CC,
+} ast_type_t;
+
+/*
+ * Represents an element within the source
+ *
+ * @left:  Left node
+ * @right: Right node
+ */
+struct ast_node {
+    struct ast_node *left;
+    struct ast_node *right;
+    union {
+        const char *s;
+        void *data;
+    };
+};
+
+/*
+ * Allocate an AST node of a specific type
+ *
+ * @state: Quip state machine
+ * @type: AST node type
+ * @res:  AST node result is written here
+ *
+ * Returns zero on success
+ *
+ */
+int ast_node_alloc(struct quip_state *state, ast_type_t type, struct ast_node **res);
+
+#endif  /* !BACKEND_AST_H */