From 6cf69df2ccd9af86a6ae1618a10d7136b30b5c49 Mon Sep 17 00:00:00 2001
From: Andre Ribeiro <33375224+Andree37@users.noreply.github.com>
Date: Wed, 31 May 2023 01:00:47 +0100
Subject: [PATCH] New example to generate AST from scratch (#507)

* feat: new example generate ast from scratch

* fix: max cols and function naming

* fix: import path
---
 examples/construct_ast_from_scratch.py | 53 ++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 examples/construct_ast_from_scratch.py

diff --git a/examples/construct_ast_from_scratch.py b/examples/construct_ast_from_scratch.py
new file mode 100644
index 00000000..6c3e12fd
--- /dev/null
+++ b/examples/construct_ast_from_scratch.py
@@ -0,0 +1,53 @@
+# -----------------------------------------------------------------
+# pycparser: construct_ast_from_scratch.py
+#
+# Tiny example of writing an AST from scratch to C code.
+#
+# Andre Ribeiro [https://github.com/Andree37]
+# License: BSD
+# -----------------------------------------------------------------
+import sys
+
+# This is not required if you've installed pycparser into
+# your site-packages/ with setup.py
+sys.path.extend(['.', '..'])
+
+from pycparser import c_ast, c_generator
+
+
+# target C code:
+# int main() {
+#     return 0;
+# }
+
+
+def empty_main_function_ast():
+    constant_zero = c_ast.Constant(type='int', value='0')
+    return_node = c_ast.Return(expr=constant_zero)
+    compound_node = c_ast.Compound(block_items=[return_node])
+    type_decl_node = c_ast.TypeDecl(declname='main', quals=[],
+                                    type=c_ast.IdentifierType(names=['int']),
+                                    align=[])
+    func_decl_node = c_ast.FuncDecl(args=c_ast.ParamList([]),
+                                    type=type_decl_node)
+    func_def_node = c_ast.Decl(name='main', quals=[], storage=[], funcspec=[],
+                               type=func_decl_node, init=None,
+                               bitsize=None, align=[])
+    main_func_node = c_ast.FuncDef(decl=func_def_node, param_decls=None,
+                                   body=compound_node)
+
+    return main_func_node
+
+
+def generate_c_code(my_ast):
+    generator = c_generator.CGenerator()
+    return generator.visit(my_ast)
+
+
+if __name__ == '__main__':
+    main_function_ast = empty_main_function_ast()
+    print("|----------------------------------------|")
+    main_function_ast.show(offset=2)
+    print("|----------------------------------------|")
+    main_c_code = generate_c_code(main_function_ast)
+    print("C code: \n%s" % main_c_code)