[cfe-dev] Is ASTPrinter supposed to emit valid C++ code?

[Roman Popov via cfe-dev]

Thanks for response!
No, I don't really need to mutate the AST.
I just had a wrong impression that AST printer is supposed to emit valid
code, since it was doing it nicely in most cases. I can certainly grab
everything I need to modify from original code.

-Roman



понедельник, 2 октября 2017 г. пользователь Richard Smith написал:

> On 29 September 2017 at 13:01, Roman Popov via cfe-dev <
> cfe-dev at lists.llvm.org
> <javascript:_e(%7B%7D,'cvml','cfe-dev at lists.llvm.org');>> wrote:
>
>> Hello,
>>
>> Is it possible to emit a valid C++ from AST?
>>
>> I've tried ASTPrinter in Clang-5.0, but it seems to emit some internal
>> Clang representations. For example for template specialization I got:
>>
>> template <typename T> struct test<T, int> : sc_core::sc_module {
>>     typedef test<type-parameter-0-0, int> this_t;
>> ...
>>
>>
>> This "type-parameter-0-0"  seem to be some Clang specifics.
>>
>
> We generally try to preserve type sugar, and printing "type-parameter-0-0"
> here is undesirable. If you could figure out how we're losing the type
> sugar and fix it, we would probably take the fix. However, while we make a
> best-effort attempt to produce valid code from the AST printer, there is in
> general no guarantee that the output is valid C++; it is intended for
> consumption primarily by humans, not by a compiler.
>
> Usually, people asking about the AST printer are trying to perform some
> kind of refactoring by mutating the AST and pretty-printing the output. We
> do not recommend this approach. Instead, we recommend that you treat the
> AST as an immutable representation of the original code, decide on what
> transformations you want to perform, and then produce a set of edits to the
> original source code that have the desired effect. Clang's Tooling library
> provides support utilities for doing this.
>
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