[clang] [llvm] [mlir] [ErrorHandling] Add reportFatalInternalError + reportFatalUsageError (NFC) (PR #138251)

[Nikita Popov via cfe-commits]

================
@@ -59,22 +59,41 @@ namespace llvm {
     ~ScopedFatalErrorHandler() { remove_fatal_error_handler(); }
   };
 
-/// Reports a serious error, calling any installed error handler. These
-/// functions are intended to be used for error conditions which are outside
-/// the control of the compiler (I/O errors, invalid user input, etc.)
-///
-/// If no error handler is installed the default is to print the message to
-/// standard error, followed by a newline.
-/// After the error handler is called this function will call abort(), it
-/// does not return.
-/// NOTE: The std::string variant was removed to avoid a <string> dependency.
+/// @deprecated Use reportFatalInternalError() or reportFatalUsageError()
+/// instead.
 [[noreturn]] void report_fatal_error(const char *reason,
                                      bool gen_crash_diag = true);
 [[noreturn]] void report_fatal_error(StringRef reason,
                                      bool gen_crash_diag = true);
 [[noreturn]] void report_fatal_error(const Twine &reason,
                                      bool gen_crash_diag = true);
 
+/// Report a fatal error that likely indicates a bug in LLVM. It serves a
+/// similar purpose as an assertion, but is always enabled, regardless of the
+/// value of NDEBUG.
+///
+/// This will call installed error handlers (or print the message by default)
+/// and then abort. This will produce a crash trace and *will* ask users to
+/// report an LLVM bug.
+[[noreturn]] void reportFatalInternalError(const char *reason);
+[[noreturn]] void reportFatalInternalError(StringRef reason);
+[[noreturn]] void reportFatalInternalError(const Twine &reason);
+
+/// Report a fatal error that does not indicate a bug in LLVM, in contexts
+/// where a more sophisticated error reporting mechanism (such as Error/Expected
+/// or DiagnosticInfo) is not supported.
+///
+/// Examples where this function should be used include invalid inputs or
+/// options, but also environment error conditions outside LLVM's control.
+/// It should also be used for known unsupported/unimplemented functionality.
----------------
nikic wrote:

reportFatalUsageError() does not crash the process (it exits gracefully with non-zero exit code).

If you mean "it would be nicer if it returned Error instead", then all of this is below:
```
/// Report a fatal error that does not indicate a bug in LLVM, in contexts
/// where a more sophisticated error reporting mechanism (such as Error/Expected
/// or DiagnosticInfo) is not supported.
```

If you *can* report the error via Error return or similar, you would of course do that, but there are many places that don't support it.

https://github.com/llvm/llvm-project/pull/138251