lld/docs/error_handling_script.md

# Error Handling Script

LLD provides the ability to hook into some error handling routines through a
user-provided script specified with `--error-handling-script=<path to the script>`
when certain errors are encountered. This document specifies the requirements of
such a script.

## Generic Requirements

The script is expected to be available in the `PATH` or to be provided using a
full path. It must be executable. It is executed in the same environment as the
parent process.

## Arguments

LLD calls the error handling script using the following arguments:

```
error-handling-script <tag> <tag-specific-arguments...>
```

The following tags are supported:

- `missing-lib`: indicates that LLD failed to find a library. The library name
  is specified as the second argument, e.g. `error-handling-script missing-lib
  mylib`
- `undefined-symbol`: indicates that given symbol is marked as undefined. The
  unmangled symbol name is specified as the second argument, e.g.
  `error-handling-script undefined-symbol mysymbol`

## Return Value

Upon success, the script is expected to return 0. A non-zero value is
interpreted as an error and reported to the user. In both cases, LLD still
reports the original error.