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New example to generate AST from scratch #507

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44 changes: 44 additions & 0 deletions examples/generate_ast.py
@@ -0,0 +1,44 @@
# -----------------------------------------------------------------
# pycparser: generate_ast.py
#
# Tiny example of writing an AST from scratch to C code.
#
# Andre Ribeiro [https://github.com/Andree37]
# License: BSD
# -----------------------------------------------------------------
from __future__ import print_function
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This is unnecessary now -- I also just removed it from other examples for consistency


from pycparser import c_ast, c_generator


# target C code:
# int main() {
# return 0;
# }


def create_your_ast():
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More descriptive name: maybe something like "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=[])
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pycparser code typically tries to wrap at 80 columns
should be easy here with all the keyword params (like you do in func_def_node)

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__':
ast = create_your_ast()
print("|----------------------------------------|")
ast.show(offset=2)
print("|----------------------------------------|")
c_code = generate_c_code(ast)
print("C code: \n%s" % c_code)