Fortran pointer functions: why does this code's behavior depend on the order of function calls? -

-

reference

The toy Fortran code below gives the call to two indicator function. That is, both functions return a pointer, in fact, they are both array indicators. They both try to do the same thing, which is to return an integer array pointer that refers to an integer array having three elements, 1, 2, and 3. The first function pointer assignment operator (=>) to point to the function pointer to point to an allocated array that holds the data, the second function allocates the block of dynamic memory, through the pointer, to store the data. The calling program only prints the elements of the returned array.

Here I feel weird.

  1. If I indicate a , the result of function1 , the results are not correct. The first element of a appears to be "clustered": a is 0 , 2 , 3 < / Code>.
  2. If I indicate the result of b for function2 , then the result is correct i b becomes 1 , 2 , 3 .
  3. Strangers still point to a to function1 after function2 change a is correct for the result of a < / Code> followed by 1 , 2 , 3 .

question

Why does this happen? The more precise, the pointer function that gives the pointer to the first element of the array for the collar that is an allocated array? The more precise still creates a side-effect on the second indicator ( a ), indicating an indicator ( b ), where the targets are from different functions, Which are written to not interact with each other?

Cavets

Let me run this Intel laptop with Ubuntu, using the GNU Fortran compiler v.4.3.3. Your results may vary, which can still be more interesting Finally, as always, this may be an operator error in my part, which will be least interesting to me.

code 

  Any integer contained in the program main, dimension (:), indicator :: a, b integer :: iia => Function1 () b = & gt; Function 2 () Do I = 1, Print 3, A (i) End! What i = 1, 3! Print *, b (i)! End function function1 () integer, amplitude (:), allocated, target :: array integer, dimension (:), indicator :: function1 allocated (array (3)) array (1) = 1 array (2) = 2 array (3) = 3 function1 = & gt; Array end function function1 function function2 (integer), amplitude (:), indicator :: function2 allocated function2 (3)) function2 (1) = 1 function2 (2) = 2 function2 (3) = 3 end function function2 main The variable of Function1 is a local variable

array , this address is " In plain sight of "keeping, but after leaving the function variable does not meaningfully address Once unchecked. A possible implementation is that the array of function1 will be placed on the stack, and when during the function1 returns, that area of ​​the stack will be free for other uses. But this is probably an estimate on an implementation - the important point is that you do not have permission to use the pointer value after the variable is undefined. Allocated variables are then automatically distributed when they go out of the area, unless you declare them with the "Save" feature.


Comments

Post a Comment

Popular posts from this blog

MySql variables and php -

-
I am getting an error with php in order to format mysql_query () in php to format this string What is the right way? SELECT SELECT SELECT (*) Agents @AgentCount; User_Agent_English, User_Angent_Oursal, US.___Gent_Aginal, COUNT (User_Agent_Percade) ACC, COUNT (*) / (AgentCount) Percentage by agents user_agent_preser order DEC limit limit 50; In PHP, how am i setting $ query $ query = "SELECT count (*) agents @ agentcount; SELECT user_agent_parsed, User_agent_original , COUNT (user_agent_parsed) ascount, COUNT (*) / (@AgentCount) as a percentage by user_agent_parced by URI date DESC limit 50 "; This exact query will work properly if I put it in MySQL directly through a command line session. Do I need to release two separate php calls from mysql_query () and store the results first? I get the following error: There is an error in your SQL syntax; Instead of using a sub-selection and instead of using the 'SELECT user_agent_parsed, user_agent_original, ne...
Read more

url rewriting - How to implement the returnurl like SO in PHP? -

-
This URL should work even after the rewrite. Is this possible? Otherwise, I can only hardcoded everything If you are trying to create a login system with redirection You need to use the HTTP_REFERER header to find out where the user came from so that you can send it back there. The best way to do this is to use something like this in your login form: // - Login php & Lt; Input type = "password" name = "password" /> & Lt; Input type = "hidden" name = "returnrelale" value = "& lt ;? php echo $ redirectURL ;? & gt;" / & Gt; & Lt; / Form & gt; Please note that some ISP, browser or proxy will delete the referrer header, so you can not rely on each user to work fully. If you use a statement, to check whether the header exists or not, you can send those users back to the homepage or whatever. Edit If you are looking to use $ _SERVER ['REQUEST_URI'], if you are running Apache It sho...
Read more

Which Python client library should I use for CouchdB? -

-
I am starting to experiment with CouchDB because it looks like we have the right solution to certain problems That all the work will be on a new project, which does not have any legacy dependency, which the client library will suggest you use, and why? If we overlap any of the OS. Freeband is available only in the collection of its ports, but asks to use the library's project website. None of those people are Ubuntu, which is only with ships, since those two OSAs are not common in libraries, I am probably installing something from source (and hopefully if I have time, then Ubuntu and FreeBSD People pack the package). For those interests, I want to use CouchDB as a convenient intermediate storage space for data passed between different services - think of a message bus system, but less formalities with. For example, we have daemons that download and pars the web page, then send an interesting bit to other daemons for further processing. Many of them are ill-defined until the...
Read more