.br
The field \fIem_defdnam\fR contains the label.
.IP "EM_ERROR none" \nau
-an error in the input.
+an error in the input that makes the rest of the data in the structure
+meaningless.
.br
\fIEM_error\fR
contains an error message.
It has size \fIem_size\fR bytes on the target machine.
.PD
.PP
+When an error occurs, \fIEM_error\fR is set to indicate the reason.
+\fIEM_error\fR also is the only means of detecting whether an error
+occurred. The EM_ERROR described above is only set when the error
+is serious enough.
+.PP
The routine \fIEM_mkcalls\fR "translates" the EM instruction indicated
by \fIinstr\fR
into calls of the procedural interface defined in \fIem_code\fR(3L).