| Description |
The $OverFlowChecks compiler directive determines whether Delphi should add code to check for integer and enum operation value overflows.
This is set Off by default, meaning that a bad integer or enum operation will pass unnoticed, revealing itself in a difficult to debug part of the code.
It is recommended to switch on $OverFlowChecks in order to detect overflows before they cause problems. This will result in the raising of an exception, allowing code testing to correctlt identify the point of failure.
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| Notes |
$OverFlowChecks is equivalent to $Q.
It can and should only be set once in your code.
The default value is $OverFlowChecks Off.
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| Related commands |
| $Q |
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Determines whether Delphi checks integer and enum bounds |
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| Example code : Trapping overflow values |
var
myNumber : Byte;
begin
// Set overflow checking on
{$OverFlowChecks On}
// A byte can hold numbers up to 255
myNumber := 255;
ShowMessage('myNumber = '+IntToStr(myNumber));
// But incrementing beyond 255 will throw an exception
Inc(myNumber);
ShowMessage('myNumber = '+IntToStr(myNumber));
end;
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| Show full unit code |
myNumber = 255
Delphi throws the EIntOverflow exception
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| Example code : Ignoring overflow values |
var
myNumber : Byte;
begin
// Set overflow checking off
{$OverFlowChecks Off}
// A byte can hold numbers up to 255
myNumber := 255;
ShowMessage('myNumber = '+IntToStr(myNumber));
// But incrementing beyond 255 will wrap around to 0
Inc(myNumber);
ShowMessage('myNumber = '+IntToStr(myNumber));
end;
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| Show full unit code |
myNumber = 255
nyNumber = 0
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