No Use of "others" in Exception Handlers (RPP05)

Level \(\rightarrow\) Required

Category

Safety:: \(\checkmark\)
Cyber:: \(\checkmark\)

Goal

Maintainability:: \(\checkmark\)
Reliability:: \(\checkmark\)
Portability:: \(\checkmark\)
Performance:
Security:

Remediation \(\rightarrow\) Low

Verification Method \(\rightarrow\) GNATcheck rule: OTHERS_In_Exception_Handlers (builtin rule)

Reference

N/A

Description

Much like the situation with others in case statements and case expressions, the use of others in exception handlers makes it possible to omit an intended specific handler for an exception, especially a new exception added to an existing set of handlers. As a result, a subprogram could return normally without having applied any recovery for the specific exception occurrence, which is likely a coding error.

Applicable Vulnerability within ISO TR 24772-2

N/A

Applicable Common Weakness Enumeration

CWE-396 - Declaration of Catch for Generic Exception

Noncompliant Code Example

procedure Noncompliant (X : in out Integer) is
begin
   X := X * X;
exception
   when others =>
      X := -1;
end Noncompliant;

Compliant Code Example

procedure Compliant (X : in out Integer) is
begin
   X := X * X;
exception
   when Constraint_Error =>
      X := -1;
end Compliant;

Notes

ISO TR 24772-2: 6.50.2 slightly contradicts this when applying exception handlers around calls to library routines:

Put appropriate exception handlers in all routines that call library routines, including the catch-all exception handler when others =>

Put appropriate exception handlers in all routines that are called by library routines, including the catch-all exception handler when others =>

ISO TR 24772-2 also recommends "All tasks should contain an exception handler at the outer level to prevent silent termination due to unhandled exceptions."