Apple

Le 30 avr. 09 à 18:17, Luis Vitorio Cargnini a écrit :

Hi all,
Sorry but whiy this:

char *c =(char *) malloc(5000*sizeof(char));

                                  c=(char *)malloc(5000*sizeof(char));

                                c=NULL;

is a leak ?

for me is only "bad" programming practice, just waste of 5000 bytes (twice), not a leak itself, the program is wasting 5000 bytes, that will be released in two moments one after the application finish, if it works as a daemon ok, your application is gathering 5000 bytes and simple not using it. Also I'm not exactly sure IF the compiler couldn't make this kind of optimization and detect this kind of waste of memory and simply "dump" the machine code, since you are initializing it will allocate the initial memory than put the pointer into the "limbo".

But this is not exactly leak for me as I said is bad programming practice, why do you say this is a leak ?

Le 09-04-30 à 11:29, mac adobe a écrit :

Hi all,

I am on lepord 10.5.7 . The following issue was also seen in 10.5.5 .

I am facing an issue with leaks utility in mac and would like your comments on the same .

I have introduced leaks explicitly in my xcode test case program through

char *p=(char*) malloc(1000*sizeof(char));

p=NULL;

As per the man pages of the leaks utility , it catches all leaked memory – memory that has been allocated but has been lost and cannot be freed . As in the above said case 1000 characters have been allocated and the only pointer to the said 1000 characters has been lost by p=NULL , I expected leaks to tell me this as a leak . However it did not .

Do we need to set any variable (environment ) etc to make leaks catch this error ?

I had set the environment variable by export MallocStackLogging=1 which is used for displaying stack trace AFTER it identifies a leak .

Has anyone else faced similar issues in the past or am I doing it the wrong way . Kindly comment .

Also I see that

1)      Many a times leaks utility gives strange behavior , identifying leaks during a run  and in subsequent runs of the same test program , not identifying leaks at all .

2)      Identifying leaks only in function calls and not in main program .

3)      Not identifying leaks at all in those cases where an external dll have been used .

Let me give you the sample code which I used test using leaks utility on mac .

Since it was not giving leaks with 1000 I increased it several times but still no help .

#include <iostream>

void callme()

{

     char *p=(char *) malloc(1024*1024*sizeof(char));

}

int main (int argc, char * const argv[]) {

     int i ;

     std::cin >>i;

std::cout << "Hello, World!\n";

     callme();

char *c =(char *) malloc(5000*sizeof(char));

     c=(char *)malloc(5000*sizeof(char));

     c=NULL;

     std::cin >>i;

   return 0;

}

1)      This code fragment was compiled and then run . and attached to instrument’s leaks utility (during call of first scanf I attached the process with leaks utility) . It is clear that callme() will lead to memory leak . However the leaks utility identified it only once and during reruns of the same test program it failed to identify this as a leak .

2)      During cases when leaks utility did identified it as a leak , it failed to identify leaks in main

                                char *c =(char *) malloc(5000*sizeof(char));

                                c=(char *)malloc(5000*sizeof(char));

                                c=NULL;

   Note that since c is pointing to memory of character 5000 and later points to another 5000 different memory , we should get a leak in main also . However leak utility

   failed to identify this as a leak .

        Please note that we did set export MallocStackLogging=1    before running the program in the same terminal window

Has anyone else faced similar issues in the past or am I doing it the wrong way . Kindly comment .

Thanks and Regards

Manish
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