Mega Code Archive
$r - determines whether delphi checks array bounds
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1 {$R FileName}
2 {$R-}
3 {$R+}
Description
The $R compiler directive has two forms. Firstly, it defines a resource file to be compiled. Secondy, it determines whether Delphi should add code for array bounds checking.
Version 1
Defines a resource file. refer to $Resource for further information.
Versions 2 and 3 This is set off (-) by default, meaning that a bad array access will pass unnoticed, revealing itself in a difficult to debug part of the code.
It is recommended to switch on $R in order to detect array bound problems. This will result in the raising of an exception, allowing code testing to correctlt identify the point of failure.
Notes
$R FileName is equivalent to $Resource FileName.
$R- is equivalent to $RangeChecks Off.
$R+ is equivalent to $RangeChecks On.
It can and should only be set once in your code.
The default value is $R-.
Related commands
$RangeChecks Determines whether Delphi checks array bounds
$Resource Defines a resource file to be included in the application linking
Array A data type holding indexable collections of data
Example code : Trapping array bound problems
var
myArray : array[1..5] of string;
i : Integer;
begin
// Set range checking on
{$R+}
// Start array assignment from 0 - normally OK, but our
// array starts at 1.
for i := 0 to 5 do
begin
myArray[i] := 'Element '+IntToStr(i);
ShowMessage('myArray['+IntToStr(i)+'] = '+myArray[i]);
end;
end;
Show full unit code
Delphi throws the ERangeError exception
Example code : Ignoring array bounds problems
var
myArray : array[1..5] of string;
i : Integer;
begin
// Set range checking off
{$R-}
// Start array assignment from 0 - normally OK, but our
// array starts at 1.
for i := 0 to 5 do
begin
myArray[i] := 'Element '+IntToStr(i);
ShowMessage('myArray['+IntToStr(i)+'] = '+myArray[i]);
end;
end;
Show full unit code
myArray[0] = Element 0
myArray[1] = Element 1
myArray[2] = Element 2
myArray[3] = Element 3
myArray[4] = Element 4
myArray[5] = Element 5
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