EXP30-PL. Do not use deprecated or obsolete functions or modules

Do not use deprecated or obsolescent functions when more secure equivalent functions are available.

Here is a list of deprecated functions along with their recommended alternatives if available:

The following modules are also deprecated:

Noncompliant Code Example (die())

This noncompliant code example tries to open a file and invokes the obsolete die() method if it fails.

my $file;
open(FILE, "<", $file) or die "error opening $file: stopped";
# work with FILE

The die() method is considered deprecated because it prints the file name and line number in which it was invoked. This information might be sensitive.

Compliant Solution (croak())

This compliant solution uses the croak() function instead of die().

use Carp;

my $file;
open(FILE, "<", $file) or croak "error opening $file: stopped";
# work with FILE

Unlike die(), croak() provides the file name and line number of the function that invoked the function that invoked croak(). This solution is more useful for application code that invokes library code; in this case, croak() and carp() also will reveal the file name and line number of the application code rather than the library code.

Exceptions

EXP30:EX0: The -t function should not be used for determining if input is interactive, but it is perfectly valid to determine if output is interactive. So it may be used on *STDOUT or *STDERR.

EXP30:EX1: There are several instances when die() and warn() are preferred over carp() and croak():

• Inside a signal handler because the behavior of croak() and carp() functions when invoked inside a signal handler are not documented.

• Outside a subroutine, that is, when used in a small Perl script. In this case, all four functions have no stack trace to indicate their calling location.

• If the string given to die() or warn() ends with a newline, then these functions do not provide any file name or line number information. Consequently, they may be invoked if given a string literal that clearly ends with a newline (and the developer clearly does not wish to reveal file name or line number information).

Risk Assessment

Using deprecated or obsolete classes or methods in program code can lead to erroneous behavior.

Automated Detection

Related Guidelines

Bibliography