From: "nobu (Nobuyoshi Nakada) via ruby-core" <ruby-core@...>
Date: 2024-02-16T06:55:49+00:00
Subject: [ruby-core:116792] [Ruby master Bug#20270] Options with `--parser=prism`

Issue #20270 has been updated by nobu (Nobuyoshi Nakada).

Description updated

JFYI: It just so happens that the second issue is not a segmentation fault.

In `pm_parse_string` call just after the warning:
```
(lldb) rp source
bits: [    U]
(struct RFile) $1 = {
  basic = (flags = 11, klass = 4301593320)
  fptr = 0x0000000128628c10
}
(lldb) p *(struct RString*)source
(struct RString) {
  basic = (flags = 11, klass = 4301593320)
  len = 4972514320
  as = {
    heap = {
      ptr = 0x0000000000000000
      aux = (capa = 0, shared = 0)
    }
    embed = (ary = "")
  }
}
```

`source` is actually a `RFile`, but is interpreted as a huge embedded `RString` that starts with a NUL char.
Its `as.embed` is beyond the boundary since VWA, it is unpredictable what can be there.


----------------------------------------
Bug #20270: Options with `--parser=prism`
https://bugs.ruby-lang.org/issues/20270#change-106815

* Author: nobu (Nobuyoshi Nakada)
* Status: Open
* Priority: Normal
* Backport: 3.0: DONTNEED, 3.1: DONTNEED, 3.2: DONTNEED, 3.3: REQUIRED
----------------------------------------
### `--dump` option
Currently `parsetree` and `prism_parsetree` bits are separated, but it seems meaningless as far as `--parser` option selects only one parser.

Why doesn't simply `--dump=parsetree` dump AST by parse.y, or PRISM AST if `--parser=prism` is given?

Actually, `ruby --dump=parsetree --parser=prism` just segfaults, because these bits and `--parser` option are separately handled.

### streaming code from stdin
```sh-session
$ echo end | ruby --parser=prism -
ruby: warning: The compiler based on the Prism parser is currently experimental and compatibility with the compiler based on parse.y is not yet complete. Please report any issues you find on the `ruby/prism` issue tracker.
-: warning: Prism support for streaming code from stdin is not currently supported
```

Nothing reported is fine, since it is not currently supported.

I was a bit curious that it looks like trying something after the warning.

```C
            if (strcmp(opt->script, "-") == 0) {
                int xflag = opt->xflag;
                VALUE rb_source = open_load_file(opt->script_name, &xflag);
                opt->xflag = xflag != 0;

                rb_warn("Prism support for streaming code from stdin is not currently supported");
                error = pm_parse_string(&result, rb_source, opt->script_name);
            }
```

Note that `open_load_file` returns `rb_stdin` when `-` is given.
This object is a `RFile`, not a `RString`, and `RSTRING_PTR(rb_source)` accesses after the object boundary.
It should just bail out, not try obviously wrong thing.

### Fix

https://github.com/nobu/ruby/tree/options-refactor
https://github.com/ruby/ruby/pull/9991




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