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Topic: Dangling pointer


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In the News (Wed 15 Feb 12)

  
  Firm finds danger in dangling pointers | The Register
Known as a dangling, or wild, pointer, the flaw was caused by an IIS service process that attempted to use memory that was already freed by the program.
The discovery means that developers and security researchers need to start considering dangling pointers as security problems as serious as buffer overflows, said Danny Allan, director of security research for Watchfire.
A dangling pointer is a software bug that occurs when a programmer creates an object in memory, uses the object, frees up the memory for reuse and then mistakenly tries to access the object again.
www.theregister.co.uk /2007/07/26/dangling_pointer_threat   (607 words)

  
 Dangling pointer - Wikipedia, the free encyclopedia
Dangling pointers in programming are pointers whose objects have since been deleted or deallocated, without modifying the value of the pointer.
The pointer still points to the location in memory where the object or data was, even though the object or data has since been deleted and the memory may now be used for other purposes.
A dangling pointer (also known as a wild pointer) is a pointer, which does not point to a valid memory location.
en.wikipedia.org /wiki/Dangling_pointer   (690 words)

  
 C programming language - Encyclopedia.WorldSearch   (Site not responding. Last check: 2007-10-12)
Pointers are used widely in C; the C string type is simply a pointer to an array of characters, and dynamic memory allocation, described below, is performed using pointers.
Arrays are accessed using pointers and pointer arithmetic; the array name is treated in most contexts as a pointer to the beginning of the array.
Although most pointers point to safe places, they can be moved to unsafe places using pointer arithmetic, the memory they point to may be deallocated and reused (dangling pointers), they may be uninitialized (wild pointers), or they may be directly assigned any value using a cast or through another corrupt pointer.
encyclopedia.worldsearch.com /c_programming_language.htm   (3802 words)

  
 Debugging C Programs
Pointer bugs arise from uninitialized pointers, dangling pointers and incorrect use of arguments to functions.
A dangling pointer refers to an area of memory which is no longer being used for its original purpose.
Since pointer bugs destroy code, even the smallest change in your program, or even a change in the order in which functions are linked together, may cause the symptoms of pointer bugs to change or disappear.
personalpages.tds.net /~edream/sl_debug.html   (1517 words)

  
 Dangling pointers
A dangling pointer is a pointer to storage that is no longer allocated.
Dangling pointers are nasty bugs because they seldom crash the program until long after they have been created, which makes them hard to find.
Programs that create dangling pointers often appear to work on small inputs, but are likely to fail on large or complex inputs.
www.ccs.neu.edu /home/will/com1205/dangling.html   (617 words)

  
 [No title]
a pointer to an object outside the heap (e.g., a pointer to a block allocated by malloc, or to a C variable).
In particular, this means that one can store pointers to malloced blocks outside the ML heap into fields of blocks living in the ML heap.
The garbage collector distinguishes case 1 from cases 2 and 3 by the fact that integers have the least significant bit set, and pointers are at least 2-byte aligned.
pauillac.inria.fr /~doligez/caml-guts/Fahndrich99.txt   (329 words)

  
 Xerox Mesa Programming - Mesa Course: 4. Pointers   (Site not responding. Last check: 2007-10-12)
A dangling pointer is usually caused by deallocating storage while a pointer to it remains.
Pointers in Mesa are declared as references to types so that the Compiler can type-check their usage.
Dereferencing a dangling pointer that used to point to a value allocated in a local procedure is undefined.
www.apearson.f2s.com /mesacourse4.html   (2292 words)

  
 Lahey Forum - Dangling pointers
A dangling pointer occurs when the thing that a pointer is pointing at becomes undefined.
Dangling pointers can be extremely difficult to detect, and in fact, the Fortran standard explicitly states that those implementing the Fortran standard have no obligation to detect a pointer in a dangling condition.
One thing that might cause a dangling pointer is to point to an allocated variable, and then to deallocate the allocatable variable without nullifying or reassigning the pointer.
www.laheyforum.com /showthread.php?t=10299   (314 words)

  
 wksht4
Pointer arithmetic automatically adjusts for the size of the data type that a pointer points to.
Note that when a pointer is passed as an argument to a function, the function does not know how much memory the pointer is pointing to (if any).
The third version should use a second pointer which is initialized to the start of the string, and this pointer should be incremented.
www.cs.rpi.edu /~lallip/cs2/wksht4   (1791 words)

  
 CPS 2342 Chapter 15
Pointer types are structured data types because pointers contain addresses rather than data.
In C++, it is legal to attach an index (in brackets) to a pointer expression.
Dereferencing a dangling pointer is a logic error that may not be detectable by the computer system.
www.kean.edu /~wmagolo/T2342/cps2342chapt15.htm   (899 words)

  
 Your Heading Goes Here
Dangling pointers are the pointer variables pointing a memory chunk freed previously by same / some other function.
Access such a memory produces most undesirable effects since the freed memory might have allocated to some other program running in memory else it might still be free, in such case the results are unpredictable leading to more confusion in code as to which part of code is creating the problem.
More over there are n number of ways to create dangling pointers but the ground rule remains the same, to keep track of de-allocation of memory.
www.geocities.com /vaibhav2410/mm.htm   (906 words)

  
 A More Seamless Checking Wrapper for Raw C++ Pointers   (Site not responding. Last check: 2007-10-12)
The "original" checked pointers component for C++ [Pike00] did a very good job of detecting many precondition violations for raw C++ pointers, including dereferencing a NULL or dangling pointer and deleting a dangling pointer.
Checked pointers are implemented by two separate components: Pointer, a template which is directly used by the client programmer, and Pointer_Map, a class which underlies Pointer, and is the workhorse for detecting pointer violations (e.g., deletion of dangling pointers).
If you take the view that raw pointers in C++ are a service providing component, then it follows that there should be a checked version of raw C++ pointers, and that this checked version should be used during the development phase of any client that relies on raw C++ pointers.
people.cs.vt.edu /~edwards/RESOLVE2002/proceedings/Hollingsworth1.html   (2770 words)

  
 [No title]   (Site not responding. Last check: 2007-10-12)
A) a dangling pointer B) an inaccessible object C) both a and b are possible D) neither a nor b is possible 30.
A) a dangling pointer B) an inaccessible object C) both a and b are possible D) neither a nor b is possible 31.
A) a dangling pointer B) a memory leak C) a null pointer D) termination of the program E) duplicate copies of not only the class objects but also the pointed-to data 36.
www.scs.unr.edu /~vogt/cit131/Week12/ch15exam.doc   (828 words)

  
 C15 Extra Notes
It is a pointer constant because the value of str itself cannot be changed by assignment.
A pointer variable is a variable whose value is the address of a location in memory.
The object or array currently pointed to by the pointer is deallocated, and the pointer is considered unassigned.
www.kean.edu /~wmagolo/T2342b/c15xtranotes.htm   (1229 words)

  
 C programming language Details, Meaning C programming language Article and Explanation Guide
C's pointers are one primary source of danger; because they are unchecked, a pointer can be made to point to any object of any type, including code, and then written to, causing unpredictable effects.
Although most pointers point to safe places, they can be moved to unsafe places using pointer arithmetic, the memory they point to may be deallocated and reused (dangling pointers), or they may be uninitialized (wild pointers).
Unlike dangling pointers, a hardware exception will arise on many modern architectures when a null pointer is dereferenced.
www.e-paranoids.com /c/c_/c_programming_language.html   (4958 words)

  
 Checkmate: Cornering C++ Dynamic Memory Errors With Checked Pointers
The result is that the representation for a checked pointer contains two data members: a C++ pointer to the memory it points to, and a timestamp of when that address was allocated.
In the case of null pointers, the value of the timestamp is meaningless.
Although the checked pointers are slow relative to the unchecked pointers, they serve their purpose well in code development.
www.cse.ohio-state.edu /~bucci/rsrg/checkmate   (1661 words)

  
 Seek 'Dangling' related info here.   (Site not responding. Last check: 2007-10-12)
A Dangling Modifier occurs when the modifier and the word it modifies are not clearly visible in one sentence.
Dangling participles occur where the first part of the sentence and the clause that follows just don’t belong together, and therefore don’t make sense.
A dangling modifier is problematic because it can potentially apply to either the subject or the object of the sentence it is attached to.
netinfoseek.com /?q=dangling   (967 words)

  
 [No title]   (Site not responding. Last check: 2007-10-12)
Show, by example, that use of pointer arithmetic can allow a function in C++ to access variables that it should not be able to access according to the binding rules of C++.
The use of pointer q in main is called a dangling pointer.
Include the static link, dynamic link (or frame pointer), and local variables (with their current values) and the return address in each activation record.
condor.depaul.edu /~glancast/447class/hw/practice03.html   (553 words)

  
 The Memory Management Glossary: D
A dangling pointer is a surviving reference to an object that no longer exists at that address
Dangling pointers can occur under automatic memory management, because of a garbage collection bug -- such as premature collection, or moving without updating all references -- but this is much rarer because GC code is usually a single common core of reused code.
An interior pointer is a pointer to memory
www.memorymanagement.org /glossary/d.html   (1391 words)

  
 "Pure Virtual Function Called": An Explanation
That's a pointer to an object that's been deleted, or memory that's been freed, or both.
If other code was executed between the deletion of the object and the use of dangling pointer, the memory allocation system might have created a new object out of some or all of the memory used by the old object.
With smart pointers, ownership belongs to the set of smart pointers that point to the object.
www.artima.com /cppsource/pure_virtual.html   (2789 words)

  
 Dangling - dangling pointer   (Site not responding. Last check: 2007-10-12)
The mission of The Dangling Modifier is to provide an international forum for ongoing conversation among peer tutors in writing.
Outdoors-Magazine.com, Dangling Knife Sheath, Here is a simple modification to a knife sheath, to let the sheath ride low on your leg rather than high.
A present participle is a verb ending in -ing, and is called dangling when One way to tell whether the participle is dangling is to put the phrase with
www.infomany.com /ifmn/dangling.htm   (223 words)

  
 Dyamic Arrays - Concepts
Delete must be passed a valid pointer, and not one that has already been deleted.
There is no simple function that you can call to test if a pointer is a dangling one.
One way to avoid such problems is to set all dangling pointers to NULL after a delete call.
www.site.uottawa.ca /~basu/notes/darrays.html   (669 words)

  
 MAINDEBUG User's Guide, Chapter 6   (Site not responding. Last check: 2007-10-12)
that will later be used becomes dangling before a certain point in the program, set a breakpoint there, and enable rigging only when the breakpoint is reached.
This is because the debugger remembers the old value of p in order to see when p changes, but the debugger's saved value changes to the rigging pattern at the same time p's value does, when the dynamic object both point to is disposed.
When it comes time to determine whether the watch breakpoint has been reached, the debugger compares the two bit patterns, and they are the same, so the debugger thinks that p has not changed.
www.xidak.com /mainsail/documentation_set_1630_html/docset-MDEBU-6.html   (1300 words)

  
 dangling pointer - BlueRider.com
In C and some other languages, a pointer that doesn't actually point at anything valid.
Usually this happens because it formerly pointed to something that has moved or disappeared, e.g.
Used as jargon in a generalisation of its technical meaning; for example, a local phone number for a person who has since moved is a dangling pointer.
dangling_pointer.bluerider.com /wordsearch/dangling_pointer   (66 words)

  
 Jargon 4.2, node: dangling pointer   (Site not responding. Last check: 2007-10-12)
[common] A reference that doesn't actually lead anywhere (in C and some other languages, a pointer that doesn't actually point at anything valid).
Usually this happens because it formerly pointed to something that has moved or disappeared.
Used as jargon in a generalization of its techspeak meaning; for example, a local phone number for a person who has since moved to the other coast is a dangling pointer.
www.science.uva.nl /~mes/jargon/d/danglingpointer.html   (68 words)

  
 SatView: Pointer Perfect, part 4
A dangling pointer is a pointer that once was pointing to the right object, but was referenced after the object it pointed at was freed.
A nasty way to create dangling pointers is to forget that the compiler implicitly creates a copy constructor and assignment operator for your class when you don’t declare them.
Because shallow was passed by value to foo() a shallow copy was constructed for it and the resulting (shallow) param inherited the pointer which it correctly freed upon leaving the function.
www.aspfree.com /c/a/C-Sharp/SatView-Pointer-Perfect-part-4/2   (900 words)

  
 Dangling Pointer
A pointer that was pointing to the right object, but the memory pointed by this pointer was then returned to the MemoryAllocationEngine?
The memory is therefore reassigned to other parts of the program, which change it at will, so the pointer seems to dangle: The data pointed to by this dangling pointer is meaningless, and dereferencing it will normally cause UndefinedBehavior.
Elimination of manual memory allocation is necessary to eliminate dangling pointers; but not sufficient.
c2.com /cgi/wiki?DanglingPointer   (209 words)

  
 dangling pointer
[common] A reference that doesn't actually lead anywhere (in C and some other languages, a pointer that doesn't actually point at anything valid).
Usually this happens because it formerly pointed to something that has moved or disappeared.
Used as jargon in a generalization of its techspeak meaning; for example, a local phone number for a person who has since moved to the other coast is a dangling pointer.
www.softlab.ece.ntua.gr /~sivann/jargon/html/entry/dangling-pointer.html   (68 words)

  
 [No title]   (Site not responding. Last check: 2007-10-12)
Solution: does not permit pointer arithmetic on *-pointer or @-pointer and provides ?-pointer which permit pointer arthmetic.
Cyclone's region analysis keeps track of what region are live at any point in the program, and does not allow the use of any pointer into a non-live region.
The printf function itself accesses the tagged arguments through a fat pointer and uses switch to make sure the arguments have the right type.
www.cse.unsw.edu.au /~nhp/component/Cyclone_Summary.html   (312 words)

  
 Insure++ Reference - READ_DANGLING   (Site not responding. Last check: 2007-10-12)
This problem occurs when an attempt is made to dereference a pointer that points to a block of memory that has been freed.
This code attempts to use a piece of dynamically allocated memory after it has already been freed.
Also check that the pointer you are using should really be pointing to a block allocated at the indicated place.
nimbus.temple.edu /insure/ref/err_redd.htm   (167 words)

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