| Issue |
71554
|
| Summary |
[Flang] Feature request/Discussion: Preprocessor/Prescanner callbacks
|
| Labels |
flang
|
| Assignees |
|
| Reporter |
tarcisiofischer
|
Hello!
I am working on a project called [Codevis](https://invent.kde.org/sdk/codevis), which is able to read C and C++ source code and extract a database representation from it, which is used (among other things) to be visualized in a graph-like structure in a Qt-based application. I am currently running some experiments to read Fortran code on Codevis, and I am using flang to do that.
I am already able to access the Fortran AST and walk around it and extract what we call the "logical representation" of the code. As for a first try, been quite easy, and I must say I really like how things are done in flang :)
The other representation on Codevis, which is the "physical representation" is not related to the data structures, but in relation to the files and inclusions. Basically, for each file, I need to get all `INCLUDE` and persist that file `a.f` depends on `b.f` given that include.
I have been able to hack the code to make it work, by adding a callback inside the Fortran preprocessor. More specifically, around here:
https://github.com/llvm/llvm-project/blob/75d6795e420274346b14aca8b6bd49bfe6030eeb/flang/lib/Parser/prescan.cpp#L896
My current hack is something like this:
```
const SourceFile *included{
allSources_.Open(path, error, std::move(prependPath))};
if (!included) {
Say(provenance, "INCLUDE: %s"_err_en_US, error.str());
} else if (included->bytes() > 0) {
ProvenanceRange includeLineRange{
provenance, static_cast<std::size_t>(p - nextLine_)};
ProvenanceRange fileRange{
allSources_.AddIncludedFile(*included, includeLineRange)};
Prescanner{*this}.set_encoding(included->encoding()).Prescan(fileRange);
if (onFortranInclude) {
(*onFortranInclude)(included->path());
}
}
```
Which is, of course, not ideal, but it works for a first experiment.
I would like to start a conversation in the direction of making ways of intercepting the preprocessor and the prescanner in such a way that I'd have access to those things without having to hack it.
Question 1: Would this be something that LLVM/Flang community would be interested in?
Question 2: Would you be open to start a conversation regarding how to proper design the solution, perhaps having clang's `PPCallback`s as an example to be followed?
If you need further information please let me know.
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