Difference between revisions of "runtime error"
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{{runtime error}} | {{runtime error}} | ||
| + | A run-time error is an irreparable error condition that arises during the [[runtime|run-time]], i.e. the execution of a [[Executable program|program]]. | ||
| − | + | == behavior == | |
| + | The [[FPC]] inserts code to detect a vast number of error situations. | ||
| + | If such a situation is encountered, the standard [[RTL|run-time library]] will initiate the termination of the program. | ||
| + | A run-time error number, and the address the error occurred at is being printed. | ||
| + | This is the safest and cheapest error treatment. | ||
| − | == | + | == comparative remarks == |
| + | === compile-time errors === | ||
| + | In contrast to [[Compile time|compile-time]] errors, which the compiler detects during compilation, run-time errors depend on the state of the program, thus can not be foreseen in advance. | ||
| + | If a compile-time error is encountered, no executable program is generated. | ||
| − | + | === exceptions === | |
| − | + | Run-time errors are the classical imperative approach in order to avoid inconsistent program states, which may eventually cause faulty program behavior. | |
| − | + | If FPC's {{Doc|package=RTL|unit=sysutils|text=<syntaxhighlight lang="pascal" enclose="none">sysUtils</syntaxhighlight> unit}} is included, all run-time errors become [[Exceptions|exceptions]] (cf. {{Doc|package=RTL|unit=system|identifier=runtimeerrors|text=<syntaxhighlight lang="pascal" enclose="none">system.runTimeErrors</syntaxhighlight>}} for details). | |
| − | + | Unlike run-time errors those can be caught by <syntaxhighlight lang="delphi" enclose="none">try … except on … do … end</syntaxhighlight> blocks, provided a mode allowing exceptions – such as [[Mode ObjFPC|<syntaxhighlight lang="pascal" enclose="none">{$mode ObjFPC}</syntaxhighlight>]] or [[Mode Delphi|<syntaxhighlight lang="pascal" enclose="none">{$mode Delphi}</syntaxhighlight>]] – is being used. | |
| − | * [https://www.freepascal.org/docs-html/ | + | A run-time error causes the program to terminate, while an exception may give the opportunity to “fix” the problem. |
| − | * [https://www.freepascal.org/docs-html/current/user/userse58.html | + | This standard behavior of {{Doc|package=RTL|unit=system|identifier=runerror|text=<syntaxhighlight lang="pascal" enclose="none">system.runError</syntaxhighlight>}} can be altered by assigning a non-[[Nil|<syntaxhighlight lang="pascal" enclose="none">nil</syntaxhighlight>]] value to {{Doc|package=RTL|unit=system|identifier=errorproc|text=<syntaxhighlight lang="pascal" enclose="none">system.errorProc</syntaxhighlight>}}. |
| + | |||
| + | == see also == | ||
| + | * [https://www.freepascal.org/docs-html/user/userap4.html Appendix D in the Free Pascal User's Guide: “Run-time errors”] | ||
| + | * [[RunError|procedure <syntaxhighlight lang="pascal" enclose="none">runError</syntaxhighlight>]] | ||
| + | * [https://www.freepascal.org/docs-html/current/user/userse58.html “Line numbers in run-time error backtraces”] in the Free Pascal User's Guide | ||
| + | * {{Doc|package=RTL|unit=system|identifier=returnnilifgrowheapfails|text=<syntaxhighlight lang="pascal" enclose="none">system.returnNilIfGrowHeapFails</syntaxhighlight>}} | ||
Revision as of 17:23, 11 March 2019
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English (en) │
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A run-time error is an irreparable error condition that arises during the run-time, i.e. the execution of a program.
behavior
The FPC inserts code to detect a vast number of error situations. If such a situation is encountered, the standard run-time library will initiate the termination of the program. A run-time error number, and the address the error occurred at is being printed. This is the safest and cheapest error treatment.
comparative remarks
compile-time errors
In contrast to compile-time errors, which the compiler detects during compilation, run-time errors depend on the state of the program, thus can not be foreseen in advance. If a compile-time error is encountered, no executable program is generated.
exceptions
Run-time errors are the classical imperative approach in order to avoid inconsistent program states, which may eventually cause faulty program behavior.
If FPC's sysUtils unit is included, all run-time errors become exceptions (cf. system.runTimeErrors for details).
Unlike run-time errors those can be caught by try … except on … do … end blocks, provided a mode allowing exceptions – such as {$mode ObjFPC} or {$mode Delphi} – is being used.
A run-time error causes the program to terminate, while an exception may give the opportunity to “fix” the problem.
This standard behavior of system.runError can be altered by assigning a non-nil value to system.errorProc.
