AT (action-time)
Determines when an implementation processes an error condition.
action-time is COMPILATION or EXECUTION.
If action-time is COMPILATION and the directive appears in the specification part of a program unit, the error action occurs during compilation. If the directive appears in the executable part of the program unit that is not reachable at runtime, the error action may or may not occur.
If action-time is EXECUTION, the error action occurs when a thread encounters the directive. An ERROR direction that specifies AT (EXECUTION) is considered an executable directive.
If an AT clause is not specified in the ERROR directive, it is as if AT (COMPILATION) was specified.
MESSAGE (scalar-default-char-expression)
Specifies a message string to be included in the implementation defined message issued when the error action occurs.
If action-time is COMPILATION, scalar-default-char-expression must be a constant.
SEVERITY (level)
Indicates the severity level of the error.
level is WARNING or FATAL.
If level is WARNING, a message containing scalar-default-char-expression is displayed and processing (compilation of execution) continues.
If level is FATAL, a message containing scalar-default-char-expression is displayed and program termination is initiated.
If a SEVERITY clause is not specified in the ERROR directive, it is as if SEVERITY (FATAL) was specified.