Segfault - Revision history

Umbire the Phantom: de-SLEX

2022-10-05T01:53:40Z

de-SLEX

Aximili: /* Core dump */ add man page link

2020-03-20T04:40:23Z

‎Core dump: add man page link

Aximili: Add cateogy, make todo use relevant template, add wikipedia link

2020-03-05T02:11:02Z

Add cateogy, make todo use relevant template, add wikipedia link

Ais523: expand

2015-11-12T01:55:42Z

expand

Bluescreenofdeath: Maybe someone can improve this, since it's mainly based on my own observations...

2015-11-09T07:57:26Z

Maybe someone can improve this, since it's mainly based on my own observations...

New page

NetHack '''segfaults''' in certain rare situations where a function expects the game to be in a state that it is not, e.g. assuming that an object exists which has already been removed from memory. Depending on the operating system used, the behavior can be slightly different; on Windows, Nethack closes and often displays a message saying "NETHACK.EXE has stopped working"; on a public server the player will be sent back to the launch screen with no message at all; and usually the player's progress on the current dungeon level will be lost. The game in question needs to be [[recover|recovered]] so the player can go on playing.

Less serious errors can cause a [[panic]], which basically also means the game is in a state it shouldn't be in, but with the difference that the programmers thought about the possibility of it happening. Segfaults, on the other hand, are situations where the code doesn't lead to a panic in the case of a faulty game state.

[[Category:Bugs]]

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 {{wikipedia|segmentation fault}}
-NetHack '''segfaults''' in certain rare situations where a function expects the game to be in a state that it is not. This always indicates a bug in the code (with the exception of the game features in [[Slash'EM Extended]] that are intentionally designed to corrupt memory). The most common reason is the nonexistence of something that a function assumes will exist.
+''[[NetHack]]'' '''segfaults''' in certain rare situations where a function expects the game to be in a state that it is not; this always indicates a bug in the code. The most common reason is the nonexistence of something that a function assumes will exist.
 == Behaviour ==

← Older revision		Revision as of 04:40, 20 March 2020
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	==Core dump==		==Core dump==
		+	{{man\|ulimit}}

	If you are working on developing a NetHack [[variant]] (or NetHack itself!) on Linux or Mac OS X, you can configure your terminal so that a segfault leads to a useful "core dump" file that can be opened in a debugger to allow you to know what went wrong. The command to use depends on the operating system and shell you are using. For Linux with <tt>bash</tt>, you can use this command before running the program:		If you are working on developing a NetHack [[variant]] (or NetHack itself!) on Linux or Mac OS X, you can configure your terminal so that a segfault leads to a useful "core dump" file that can be opened in a debugger to allow you to know what went wrong. The command to use depends on the operating system and shell you are using. For Linux with <tt>bash</tt>, you can use this command before running the program:

@@ Line 1: / Line 1: @@
-NetHack '''segfaults''' in certain rare situations where a function expects the game to be in a state that it is not. This always indicates a bug in the code (with the exception of the game features in [[Slash'EM Extended]] that are intentionally designed to corrupt memory). The most common reason is the nonexistence of something that a function assumes will exist (either a NULL pointer) Depending on the operating system used, the behavior can be slightly different; on Windows, Nethack closes and often displays a message saying "NETHACK.EXE has stopped working"; on Linux, you normally get a "Segmentation fault" error message printed at whatever location the cursor happens to be onscreen (followed by a prompt); and most public servers will handle the segmentation fault internally and just send you back to the launch screen (eu.un.nethack.nu additionally sends a message to its IRC channel when this happens).
+{{wikipedia|segmentation fault}}
-A segfault will leave files on disk exactly as-is, without any attempt to save the game. In most cases (i.e. any codebase that is not derived from [[NitroHack]], with the INSURANCE compile-time configuration option set and the in-game [[options#checkpoint|checkpoint]] option set), the game will be left in a state where it needs [[recover]]y, and after recovery, will return the game to the state at which it was in when the player entered their current dungeon level, or saved (whichever is more recent). In [[DynaHack]] and [[NetHack 4]] (and theoretically in [[NitroHack]], although the mechanism normally fails in practice), the game will normally be able to recover from a segfault automatically (returning to the start of the turn in DynaHack, or the exact point of the segfault in NetHack 4), although if the bug that caused it has not been fixed in the meantime, the game will normally segfault in the exact same way again.
+NetHack '''segfaults''' in certain rare situations where a function expects the game to be in a state that it is not. This always indicates a bug in the code (with the exception of the game features in [[Slash'EM Extended]] that are intentionally designed to corrupt memory). The most common reason is the nonexistence of something that a function assumes will exist.
 In the case where the game can detect an impossible state before it happens, you get a [[panic]] instead. This has clearer messages than a segfault, and often recovers in a different way, because the game has a chance to handle it. (For example, sometimes you will get an "emergency save" file created.)
 If you are working on developing a NetHack [[variant]] (or NetHack itself!) on Linux or Mac OS X, you can configure your terminal so that a segfault leads to a useful "core dump" file that can be opened in a debugger to allow you to know what went wrong. The command to use depends on the operating system and shell you are using. For Linux with <tt>bash</tt>, you can use this command before running the program:
@@ Line 9: / Line 17: @@
   ulimit -Sc unlimited
-:''TODO: commands for other shells and operating systems''
+{{todo|commands for other shells and operating systems}}
 Note that many operating systems will only save one core dump (per program, or per working directory) at a time, so you will need to delete the old one before you can get new ones.
 [[Category:Bugs]]