begin removal of global error_state variable * gripes.h, gripes.cc (gripe_library_execution_error): Delete. * error.cc (warning_state): Delete unused variable. (reset_error_handler): Don't set warning_state or error_state. (debug_or_throw_exception): New static function. (verror): Don't check error_state. (vmessage): Call debug_or_throw_exception instead of setting error_state. (error_1, error_2): Combine into single function, error_1 that prints error message and ultimately calls debug_or_throw_exception. (verror, verror_with_cfn, verror_with_id_cfn): Call error_1. Don't check or set warning_state. (error): Don't check error_state. (Flasterror, Flasterr): Adapt to not using error_state. (interpreter_try): Don't unwind_protect error_state. * NEWS: Update. * doc/interpreter/external.txi: Explain octave_execution_exception instead of error_state for matrix addition example. * jit-typeinfo.cc (octave_jit_gripe_nan_to_logical_conversion, octave_jit_ginvalid_index, octave_jit_gindex_range, octave_jit_paren_scalar, octave_jit_paren_scalar_subsasgn): Don't catch octave_execution_exception. * cellfun.cc (Fcellfun): Use exceptions instead of error_state. * ls-mat-ascii.cc (save_mat_ascii_data): Likewise. * mex.cc (mexCallMATLAB, mexEvalString): Likewise. * variables.cc (safe_symbol_lookup): Likewise. * svd.cc (Fsvd): Eliminate use of error_state. * __magick_read__.cc (read_file, write_file): Likewise. * variables.cc (generate_struct_completions): Eliminate use of obsolete warning_state variable. * ov-builtin.cc (octave_builtin::do_multi_index_op): Don't catch octave_execution_exception and call gripe_library_execution_error. * ov-class.cc (octave_class::reconstruct_exemplar): Eliminate use of error_state. Catch possible octave_execution_exception in do_multi_index_op. * ov-mex-fcn.cc (octave_mex_function::do_multi_index_op): Eliminate use of error_state. Catch possible octave_execution_exception in call_mex. * ov-fcn-handle.cc (octave_fcn_binder::maybe_binder): Eliminate use of error_state. * ov-oncleanup.cc (octave_oncleanup::~octave_oncleanup): Eliminate use of error_state. Propagate possible octave_execution_exception from do_multi_index_op. * ov.cc (octave_value::assign, do_binary_op, do_unary_op, octave_value::do_non_const_unary_op): Don't catch octave_execution_exception here. * oct-parse.in.yy (octave_base_parser::finish_colon_expression, octave_base_parser::finish_array_list): Eliminate use of warning_state and error_state. (Feval, Fevalin): Use exceptions instead of error_state. * pt-eval.cc, pt-eval.h (tree_evaluator::unwind_protect_exception): New static variable. * (tree_evaluator::visit_statement): Don't catch octave_execution_exception here. (tree_evaluator::visit_try_catch_command, tree_evaluator::do_unwind_protect_cleanup): Eliminate use of error_state. (tree_evaluator::visit_unwind_protect_command): Use unwind_protect_exception to track whether an exception has occurred in the try block.

--- a/libinterp/corefcn/mex.cc
+++ b/libinterp/corefcn/mex.cc
@@ -3105,9 +3105,20 @@
   for (int i = 0; i < nargin; i++)
     args(i) = mxArray::as_octave_value (argin[i]);
 
-  octave_value_list retval = feval (fname, args, nargout);
-
-  if (error_state && mex_context->trap_feval_error == 0)
+  bool execution_error = false;
+
+  octave_value_list retval;
+
+  try
+    {
+      retval = feval (fname, args, nargout);
+    }
+  catch (const octave_execution_exception&)
+    {
+      execution_error = true;
+    }
+
+  if (execution_error && mex_context->trap_feval_error == 0)
     {
       // FIXME: is this the correct way to clean up?  abort() is
       // going to trigger a long jump, so the normal class destructors
@@ -3138,13 +3149,7 @@
   while (num_to_copy < nargout)
     argout[num_to_copy++] = 0;
 
-  if (error_state)
-    {
-      error_state = 0;
-      return 1;
-    }
-  else
-    return 0;
+  return execution_error ? 1 : 0;
 }
 
 void
@@ -3163,14 +3168,19 @@
 
   octave_value_list ret;
 
-  ret = eval_string (s, false, parse_status, 0);
-
-  if (parse_status || error_state)
+  bool execution_error = false;
+
+  try
     {
-      error_state = 0;
-
-      retval = 1;
+      ret = eval_string (s, false, parse_status, 0);
     }
+  catch (const octave_execution_exception&)
+    {
+      execution_error = true;
+    }
+
+  if (parse_status || execution_error)
+    retval = 1;
 
   return retval;
 }