VCL Exception Classes

Go Up to Handling Exceptions in VCL Applications

VCL includes a large set of built-in exception classes for automatically handling divide-by-zero errors, file I/O errors, invalid typecasts, and many other exception conditions. All VCL exception classes descend from one root object called System.SysUtils.Exception. Exception provides a consistent interface for applications to handle exceptions. It provides the string for the message that VCL exceptions display by default.

The following table lists a selection of the exception classes defined in VCL:

Selected exception classes :

Exception class	Description
EAbort	Stops a sequence of events without displaying an error message dialog box.
EAccessViolation	Checks for invalid memory access errors.
EBitsError	Prevents invalid attempts to access a Boolean array.
EComponentError	Signals an invalid attempt to register or rename a component.
EConvertError	Indicates string or object conversion errors.
EDatabaseError	Specifies a database access error.
EDBEditError	Catches data incompatible with a specified mask.
EDivByZero	Catches integer divide-by-zero errors.
EExternalException	Signifies an unrecognized exception code.
EInOutError	Represents a file I/O error.
EIntOverflow	Specifies integer calculations whose results are too large for the allocated register.
EInvalidCast	Checks for illegal typecasting.
EInvalidGraphic	Indicates an attempt to work with an unrecognized graphic file format.
EInvalidOperation	Occurs when invalid operations are attempted on a component.
EInvalidPointer	Results from invalid pointer operations.
EMenuError	Involves a problem with menu item.
EOleCtrlError	Detects problems with linking to ActiveX controls.
EOleError	Specifies OLE automation errors.
EPrinterError	Signals a printing error.
EPropertyError	Occurs on unsuccessful attempts to set the value of a property.
ERangeError	Indicates an integer value that is too large for the declared type to which it is assigned.
ERegistryException	Specifies registry errors.
EZeroDivide	Catches floating-point divide-by-zero errors.

There are other times when you will need to create your own exception classes to handle unique situations. You can declare a new exception class by making it a descendant of type Exception and creating as many constructors as you need (or copy the constructors from an existing class in the SysUtils unit).

Topics

• Silent Exceptions
• Integer Exceptions
• Floating-Point Exceptions
  • Floating-Point Exception: Divide by 0, Domain or Overflow
  • Floating-Point Exception: Partial Loss of Precision or Underflow
  • Floating-Point Exception: Stack Fault

See Also

• Default Exception Handling in VCL
• Defining Your Own VCL Exceptions

• Exception Handling in C++Builder