function keys - Page 133

Save or update for FK relationship Sqlalchemy

- by Alex

I've googled, but haven't been able to find the answer to this seemingly simple question. I have two relations, a customer and an order. Each order is associated to a single cusomter, and therefore has a FK relationship to the customer table. The customer relation only stores customer names, and I have set a unique constraint on the customer table barring duplicate names. Let's say I create a new order instance and set a customer for the order. Something like: order_instance.customer = Customer("customer name") When I save the order instance, SqlAlchemy will complain if a customer with this name already exists in the customer table. How do I specify to SqlAlchemy to insert into the customer table if a customer with this name doesn't already exist, or just ignore (or even update) to the customer relation? I don't really want to have to check each time if a customer with some name already exists...

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When to use a foreign key in MySQL

- by Mel

Is there official guidance or a threshold to indicate when it is best practice to use a foreign key in a MySQL database? Suppose you created a table for movies. One way to do it is to integrate the producer and director data into the same table. (movieID, movieName, directorName, producerName). However, suppose most directors and producers have worked on many movies. Would it be best to create two other tables for producers and directors, and use a foreign key in the movie table? When does it become best practice to do this? When many of the directors and producers are appearing several times in the column? Or is it best practice to employ a foreign key approach at the start? While it seems more efficient to use a foreign key, it also raises the complexity of the database. So when does the trade off between complexity and normalization become worth it? I'm not sure if there is a threshold or a certain number of cell repetitions that makes it more sensible to use a foreign key. I'm thinking about a database that will be used by hundreds of users, many concurrently. Many thanks!

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SQL Server 2008: The columns in table do not match an existing primary key or unique constraint

- by 109221793

Hi guys, I need to make some changes to a SQL Server 2008 database. This requires the creation of a new table, and inserting a foreign key in the new table that references the Primary key of an already existing table. So I want to set up a relationship between my new tblTwo, which references the primary key of tblOne. However when I tried to do this (through SQL Server Management Studio) I got the following error: The columns in table 'tblOne' do not match an existing primary key or UNIQUE constraint I'm not really sure what this means, and I was wondering if there was any way around it?

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Foreign key definition in sqlite

- by Hab

Cant add foreign key constraint in sqlite ...........

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how to save related models with non-null foreign key

- by Fortress

I have a model called user which has_one email. I put the foreign key (NOT NULL) inside users table. Now I'm trying to save it in the following way: @email = Email.new(params[:email]) @email.user = User.new(params[:user]) @email.save This raises a db exception, because the foreign key constraint is not met (NULL is inserted into email_id). How can I elegantly solve this or is my data modeling wrong?

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List all foreign key constraints that refer to a particular column in a specific table

- by Sid

I would like to see a list of all the tables and columns that refer (either directly or indirectly) a specific column in the 'main' table via a foreign key constraint that has the ON DELETE=CASCADE setting missing. The tricky part is that there would be an indirect relationships buried across up to 5 levels deep. (example: ... great-grandchild- FK3 = grandchild = FK2 = child = FK1 = main table). We need to dig up the leaf tables-columns, not just the very 1st level. The 'good' part about this is that execution speed isn't of concern, it'll be run on a backup copy of the production db to fix any relational issues for the future. I did SELECT * FROM sys.foreign_keys but that gives me the name of the constraint - not the names of the child-parent tables and the columns in the relationship (the juicy bits). Plus the previous designer used short, non-descriptive/random names for the FK constraints, unlike our practice below The way we're adding constraints into SQL Server: ALTER TABLE [dbo].[UserEmailPrefs] WITH CHECK ADD CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] FOREIGN KEY([UserId]) REFERENCES [dbo].[UserMasterTable] ([UserId]) ON DELETE CASCADE GO ALTER TABLE [dbo].[UserEmailPrefs] CHECK CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] GO The comments in this SO question inpire this question.

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Way to check for foreign key references before deleting in MySQL?

- by Chad Johnson

I'm working with a content management system, and users are prompted with a confirmation screen before deleting records. Some records are foreign key referenced in other tables, and therefore they cannot be deleted. I would like to display a message beside a given record if it has foreign key references. To know whether I should display the message for a record, I could just query the referencing table and see if there are references. But the problem is, there are about a dozen tables with records potentially referencing this record, and a lookup could take a "long" time. Is there an easy way to tell whether the record is delete-ready (ie. has no foreign key references)?

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MYSQL inserting records form table A into tables B and C (linked by foreign key) depending on column values in table A

- by Chez

Hi All, Have been searching high and low for a simple solution to a mysql insert problem. The problem is as follows: I am putting together an organisational database consisting of departments and desks. A department may or may not have n number of desks. Both departments and desks have their own table linked by a foreign key in desks to the relevant record in departments (i.e. the pk). I have a temporary table which I use to place all new department data (n records long)...In this table n number of desk records for a department follow the department record directly below. In the TEMP table, if a column department_name has a value,it is a department, if it doesn't it will have a value for the column desk and therefore will be a desk which is related to the above department. As I said there maybe several desk records until you get to the next department record. Ok, so what I want to do is the following: Insert the departments into the departments table and its desks into the desks table , generating a foreign key in the desk record to the relevant departments id. In pseudo-ish code: for each record in TEMP table if Department INSERT the record into Departments get the id of the newly created Department record and store it somewhere else if Desk INSERT the desk into the desks table with the relevant departments id as the foreignkey note once again that all departments desks directly follow the department in the TEMP Table Many Thanks

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Jump-To-Code-Line Eclipse Shortcuts

- by scrr

Hello, is it possible, in Eclipse, to mark certain lines with Shortcuts and be able to quickly jump to those lines? Example: Let's say I have maintenanceHeavyMethod() at line 120 in my class, gameLoop() at line 800 and some listener at line 1460. I'd like to f.ex. press CTRL-SHIFT-1, 2, 3 etc. to mark those positions, and then use f.ex. CTRL-1, 2, 3 to immediately jump to them. I don't like split-screens etc, but I need to jump around when writing. Is there such a feature? I'm using latest Eclipse to write Java-programs.

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Django: getting the list of related records for a list of objects

- by Silver Light

Hello! I have two models related one-to many: class Person(models.Model): name = models.CharField(max_length=255); surname = models.CharField(max_length=255); age = models.IntegerField(); class Dog(models.Model): name = models.CharField(max_length=255); owner = models.ForeignKey('Person'); I want to output a list of persons below each person a list of dogs he has. Here's how I can do it: in view: persons = Person.objects.all()[0:100]; in template: {% for p in persons %} {{ p.name }} has dogs:<br /> {% for d in persons.dog_set.all %} - {{ d.name }}<br /> {% endfor %} {% endfor %} But if I do it like that, Django will execute 101 SQL queries which is very inefficient. I tried to make a custom manager, which will get all the persons, then all the dogs and links them in python, but then I can't use paginator (my another question: http://stackoverflow.com/questions/2532475/django-paginator-raw-sql-query ) and it looks quite ugly. Is there a more graceful way doing this?

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How can I ask Hibernate to create an index on a foreign key (JoinColumn)?

- by Kent Chen

Hi, This is my model. class User{ @CollectionOfElements @JoinTable(name = "user_type", joinColumns = @JoinColumn(name = "user_id")) @Column(name = "type", nullable = false) private List<String> types = new ArrayList<String>(); } You can imagin there would be a table called "user_type", which has two columns, one is "user_id", the other is "type". And when I use hbm2ddl to generate the ddls, I can have this table, along with the foreign key constraint on "user_id". However, there is no index of this for this column. And I need this index. How can I let hibernate to generate this index for me? Thank you!

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Why can't I SELECT a parent field that doesn't have a child?

- by myaccount

(rest_branches) is the table of restaurants. (phone_numbers) is another table which contains the restaurants phone_numbers, and it has a field called (branch_id) which references the restaurant id. When I try: SELECT * FROM rest_branches NATURAL JOIN phone_numbers I only get the restaurants which have a phone_number. What should I do to get all restaurants even if they don't have a phone number?

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MySql Query to return number of photos in each album

- by GivenPie

MY table is set up like this, all I need to do is call a query to my Photos table. I have PhotoID as the primary key and GalleryID as the foreign key to Gallery. How can I could the number of unique PhotoID's for each multiple GalleryIDs. So to speak there are may duplicate GalleryIDs because there are many photos in a gallery. So I just need to could the number of unique PhotoIDs associated with that GalleryID. Can it be done in one query?

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Maximum Length for a foreign key in DB2? (SQL0107N)

- by IronGoofy

We have two installations of DB2. When defining a foreign key with a long name, it works fine on one instance, but not on the other (we get a SQL0107N Name too long - max length is 18). What is causing this different behaviour? Is there a parameter we can change or is it version dependant?

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Generate Delete Statement From Foreign Key Relationships in SQL 2008 ?

- by Element

Is it possible via script/tool to generate a delete statement based on the tables fk relations. i.e. I have the table: DelMe(ID) and there are 30 tables with fk references to its ID that I need to delete first, is there some tool/script that I can run that will generate the 30 delete statements based on the FK relations for me ? (btw I know about cascade delete on the relations, I can't use it in this existing db) I'm using Microsoft SQL Server 2008

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FFMpeg-PHP Installation Error

- by tundoopani

While installing FFmpeg-PHP, I got this interesting error: /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c: In function 'zim_ffmpeg_movie_getAudioStreamId': /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1051: error: 'CODEC_TYPE_AUDIO' undeclared (first use in this function) /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c: In function 'zim_ffmpeg_movie_getAudioChannels': /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1089: error: 'CODEC_TYPE_AUDIO' undeclared (first use in this function) /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c: In function 'zim_ffmpeg_movie_getAudioSampleRate': /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1125: error: 'CODEC_TYPE_AUDIO' undeclared (first use in this function) /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c: In function 'zim_ffmpeg_movie_getAudioBitRate': /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1161: error: 'CODEC_TYPE_AUDIO' undeclared (first use in this function) /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c: In function 'zim_ffmpeg_movie_getVideoBitRate': /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1181: error: 'CODEC_TYPE_VIDEO' undeclared (first use in this function) /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c: In function '_php_read_av_frame': /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1204: error: 'CODEC_TYPE_VIDEO' undeclared (first use in this function) /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1215: warning: implicit declaration of function 'avcodec_decode_video' /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1219: error: 'PKT_FLAG_KEY' undeclared (first use in this function) /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c: In function '_php_get_av_frame': /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1246: error: 'CODEC_TYPE_VIDEO' undeclared (first use in this function) /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1282: error: 'AVCodecContext' has no member named 'hurry_up' /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1284: error: 'AVCodecContext' has no member named 'hurry_up' /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c: In function '_php_get_sample_aspect_ratio': /usr/downloads/ffmpeg-php-0.6.0/ffmpeg_movie.c:1443: error: 'CODEC_TYPE_VIDEO' undeclared (first use in this function) make: *** [ffmpeg_movie.lo] Error 1 When I ran php -r 'phpinfo();' | grep ffmpeg, I got this: PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/modules/ffmpeg.so' - libavformat.so.52: cannot open shared object file: No such file or directory in Unknown on line 0 Any idea how I can fix this? I am running on Centos. Thanks in advance :)

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Help improving a simple assembly function

- by MPelletier

I just handed in this function in an assignment. It is done (hence no homework tag). But I would like to see how this can be improved. Essentially, the function sums the squares of all the integers between 1 and the given number, using the following formula: n(n+1)(2n+1)/6 Where n is the maximum number. The function below is made to catch any overflow and return 0 should any occur. UInt32 sumSquares(const UInt32 number) { int result = 0; __asm { mov eax, number //move number in eax mov edx, 2 //move 2 in edx mul edx //multiply (2n) jo end //jump to end if overflow add eax, 1 //addition (2n+1) jo end //jump to end if overflow mov ecx, eax //move (2n+1) in ecx mov ebx, number //move number in ebx add ebx, 1 //addition (n+1) jo end //jump to end if overflow mov eax, number //move number in eax for multiplication mul ebx //multiply n(n+1) jo end //jump to end if overflow mul ecx //multiply n(n+1)(2n+1) jo end //jump to end if overflow mov ebx, 6 //move 6 in ebx div ebx //divide by 6, the result will be in eax mov result, eax //move eax in result end: } return result; } Basically, I want to know what I can improve in there. In terms of best-practices mostly. One thing sounds obvious: smarter overflow check (with a single check for whatever maximum input would cause an overflow).

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Problems calling Cufon.Replace from within a function

- by Kenny Bones

Hi, I'm doing a content loader and the content that gets loaded needs some Cufon action. And that doesn't work right now since I only apply Cufon when the initial page loads. And not the newly loaded content. Now, shouldn't this be working? function loadContent() { $('#content').load(toLoad,'',showNewContent()) Cufon.replace('h1, h2, h3, h4, .menuwrapper', { fontFamily: 'advent'});} Or am I not getting something? I've also tried calling Cufon.Replace right after the procedure that calls the loadContent function, but that only applies the Cufon the next time I click a link. $('.dynload').live('click', function(){ var toLoad = $(this).attr('href')+' #content'; $('#content').fadeOut('fast',loadContent); $('#ajaxloader').fadeIn('normal'); window.location.hash = $(this).attr('href').substr(0,$(this).attr('href').length); Cufon.replace('h1, h2, h3, h4, .menuwrapper', { fontFamily: 'advent'}); How can I make sure Cufon is applied as soon as possible after loading new content? I was thinking about calling Cufon.replace the moment before the new content is faded in. But this doesn't seem to be working.

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how to use units along function parameter values in Mathematica

- by niko

I would like to pass the parameter values in meters or kilometers (both possible) and get the result in meters/second. I've tried to do this in the following example: u = 3.986*10^14 Meter^3/Second^2; v[r_, a_] := Sqrt[u (2/r - 1/a)]; Convert[r, Meter]; Convert[a, Meter]; If I try to use the defined function and conversion: a = 24503 Kilo Meter; s = 10198.5 Meter/Second; r = 6620 Kilo Meter; Solve[v[r, x] == s, x] The function returns the following: {x -> (3310. Kilo Meter^3)/(Meter^2 - 0.000863701 Kilo Meter^2)} which is not the user-friendly format. Anyway I would like to define a and r in meters or kilometers and get the result s in meters/second (Meter/Second). I would be very thankful if anyone of you could correct the given function definition and other statements in order to get the wanted result.

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About function scopes in javascript

- by Shawn

Look at the code below. I want to alert the value of i at the moment that specific listener was added. Is other words, clicking each marker should alert a different value. Where can I store the value of i in a way that it won't change and be accessible inside the scope of that function? Here is problematic code: (it is difficult to test because you need a key from Google) <html> <head> <title>a</title> <script type="text/javascript"> function init() { map = new GMap2(document.getElementById("map_canvas")); // http://code.google.com/intl/es/apis/maps/documentation/reference.html#GMap2 map.setCenter(new GLatLng(0, 0), 1); // http://code.google.com/intl/es/apis/maps/documentation/reference.html#GMap2.setCenter for(var i = 0; i < 10; i++) { var marker = new GMarker(point); // http://code.google.com/intl/es/apis/maps/documentation/reference.html#GMarker map.addOverlay(marker); // http://code.google.com/intl/es/apis/maps/documentation/reference.html#GMap2.addOverlay GEvent.addListener(marker, "click", function() // http://code.google.com/intl/es/apis/maps/documentation/reference.html#GEvent.addListener { alert(i); // Problem: I want the value of i at the moment when the listener is added. }); } } window.onload = init; </script> </head> <body id="map_canvas"> </body> </html> Thanks!

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Returning ifstream in a function

- by wrongusername

Here's probably a very noobish question for you: How (if at all possible) can I return an ifstream from a function? Basically, I need to obtain the filename of a database from the user, and if the database with that filename does not exist, then I need to create that file for the user. I know how to do that, but only by asking the user to restart the program after creating the file. I wanted to avoid that inconvenience for the user if possible, but the function below does not compile in gcc: ifstream getFile() { string fileName; cout << "Please enter in the name of the file you'd like to open: "; cin >> fileName; ifstream first(fileName.c_str()); if(first.fail()) { cout << "File " << fileName << " not found.\n"; first.close(); ofstream second(fileName.c_str()); cout << "File created.\n"; second.close(); ifstream third(fileName.c_str()); return third; //compiler error here } else return first; } EDIT: sorry, forgot to tell you where and what the compiler error was: main.cpp:45: note: synthesized method ‘std::basic_ifstream<char, std::char_traits<char> >::basic_ifstream(const std::basic_ifstream<char, std::char_traits<char> >&)’ first required here EDIT: I changed the function to return a pointer instead as Remus suggested, and changed the line in main() to "ifstream database = *getFile()"; now I get this error again, but this time in the line in main(): main.cpp:27: note: synthesized method ‘std::basic_ifstream<char, std::char_traits<char> >::basic_ifstream(const std::basic_ifstream<char, std::char_traits<char> >&)’ first required here

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Adding AJAX call to function triggered popup blocker

- by jerrygarciuh

Hi folks, I have a client who wants to open variously sized images in a centered popup. I tried to get them to use FancyBox but they don't want interstitial presentation, so... I initially was opening a generic popup which resized and centered onload based on image size but they don't like the shift so I added a PHP script to echo the sizes and used jQuery to fetch the size info to feed into the pop up call. But it appears the delay this causes is setting off all popup blockers. Here is the JS $("#portfolioBigPic").click(function () { var src = $("#portfolioBigPic").attr('src'); var ar = src.split('/'); var fname = ar.pop(); fname = '/g/portfolio/clients/big/' + fname; $.get("imgsize.php", { i: fname}, function(data){ var dim = data.split(","); popit(fname,dim[0],dim[1]); }); }); function popit(img,w,h) { var features = 'width='+w+',height='+h+', toolbar=0, location=0, directories=0, status=0, menubar=0, scrollbars=0, resizable=1,'; var left = (screen.width/2)-(w/2); var top = 0; features += 'top='+top+',left='+left; bigpic = window.open('portfolioBigPic.php?img='+img, 'bigpic',features); bigpic.focus(); } The only difference between dodging the blockers and failing is that I added the AJAX .get and use it to specify w and h. Any thoughts on how to avoid this? Maybe I should use PHP to get widths and heights of all the big pics and write a JS array of them when this page loads? Am I right that the delay caused by fetching the data is tripping the blockers? Thoughts? Any advice much appreciated. JG

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Troubleshooting PG Function

- by Grasper

I have this function: CREATE OR REPLACE FUNCTION CREATE_AIRSPACE_AVAILABILITY_RECORD (cur_user VARCHAR, start_time VARCHAR, start_date VARCHAR, end_time VARCHAR, end_date VARCHAR, airspace_name VARCHAR) RETURNS VOID AS ' DECLARE c_user ALIAS for $1; BEGIN IF start_time IS NULL OR start_date IS NULL OR end_time IS NULL OR end_date IS NULL THEN INSERT INTO c_user.AIRSPACE_AVAILABILITY (ASP_AIRSPACE_NM, ASA_TIME_ID, ASA_START_DT, ASA_END_DT) SELECT airspace_name, 1, ABP.ABP_START_DT, ABP.ABP_STOP_DT FROM ABP WHERE EXISTS (SELECT ASP.ASP_AIRSPACE_NM FROM AIRSPACE ASP WHERE ASP.ASP_AIRSPACE_NM = airspace_name); ELSIF start_time IS NOT NULL AND start_date IS NOT NULL AND end_time IS NOT NULL AND end_date IS NOT NULL THEN INSERT INTO c_user.AIRSPACE_AVAILABILITY (ASP_AIRSPACE_NM, ASA_TIME_ID, ASA_START_DT, ASA_END_DT) SELECT airspace_name, 1, TO_DATE(start_date||start_time,''YYMMDDHH24MI''), TO_DATE(end_date||end_time,''YYMMDDHH24MI'') FROM DUAL WHERE EXISTS (SELECT ASP.ASP_AIRSPACE_NM FROM c_user.AIRSPACE ASP WHERE ASP.ASP_AIRSPACE_NM = airspace_name); END IF; END ; ' LANGUAGE plpgsql; I try calling it like so: select * from CREATE_AIRSPACE_AVAILABILITY_RECORD('user1','','','','',''); and I get this error: ERROR: schema "c_user" does not exist SQL state: 3F000 Context: SQL statement "INSERT INTO c_user.AIRSPACE_AVAILABILITY (ASP_AIRSPACE_NM, ASA_TIME_ID, ASA_START_DT, ASA_END_DT) SELECT $1 , 1, TO_DATE( $2 || $3 ,'YYMMDDHH24MI'), TO_DATE( $4 || $5 ,'YYMMDDHH24MI') FROM DUAL WHERE EXISTS (SELECT ASP.ASP_AIRSPACE_NM FROM c_user.AIRSPACE ASP WHERE ASP.ASP_AIRSPACE_NM = $1 )" PL/pgSQL function "create_airspace_availability_record" line 23 at SQL statement Why isn't c_user being replaced with my param (user1)?

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javasript function

- by user289346

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function's return address is different from its supposed value, buffer overflow,

- by ultrajohn

Good day everyone! I’m trying to understand how buffer overflow works. I’m doing this for my project in a computer security course I’m taking. Right now, I’m in the process of determining the address of the function’s return address which I’m supposed to change to perform a buffer overflow attack. I’ve written a simple program based from an example I’ve read in the internet. What this program does is it creates an integer pointer that will be made to point to the address of the function return address in the stack. To do this, (granted I understand how a function/program variables get organized in the stack), I add 8 to the buffer variable’ address and set it as the value of ret. I’m not doing anything here that would change the address contained in the location of func’s return address. here's the program: Output of the program when gets excecuted: As you can see, I’m printing the address of the variables buffer and ret. I’ve added an additional statement printing the value of the ret variable (supposed location of func return address, so this should print the address of the next instruction which will get executed after func returns from execution). Here is the dump which shows the supposed address of the instruction to be executed after func returns. (Underlined in green) As you can see, that value is way different from the value printed contained in the variable ret. My question is, why are they different? (of course in the assumption that what I’ve done are all right). Else, what have I done wrong? Is my understanding of the program’s runtime stack wrong? Please, help me understand this. My project is due nextweek and I’ve barely touched it yet. I’m sorry if I’m being demanding, I badly need your help.

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