Is it possible to check if a pointer has been malloc'd in C?

[dreiko466]

Hello again,

i am looking for a way to check if a pointer has been malloc'd.
I want to use this in a way, if the pointer has not been malloc'd to be malloc'd like that:

    if ( ! (is the pointer malloc'd))   {
        pointer = malloc(.....);
    }
 

so how can i check that ,is it possible....?
I searched the google and found no answer...

Thank you for your help....

[Savage]

Hello again,

i am looking for a way to check if a pointer has been malloc'd.
I want to use this in a way, if the pointer has not been malloc'd to be malloc'd like that:

    if ( ! (is the pointer malloc'd))   {
        pointer = malloc(.....);
    }
 

so how can i check that ,is it possible....?
I searched the google and found no answer...

Thank you for your help....

It is.
If malloc fails,it sets the pointer to NULL.

[weaknessforcats]

Which is to say that unless you initialize all of your pointers to NULL, you can't tell if they've been malloc'd or not.

[dreiko466]

Thank you very much, i didn't know that,

but if it returns NULL the pointer will lost its previus value so i will have a memory leak, is any way i can check that without this memory leak???

[weaknessforcats]

but if it returns NULL the pointer will lost its previus value so i will have a memory leak, is any way i can check that without this memory leak???

Nope.

If your pointer has been malloc'd, then you need to call free() on it before you use it in another malloc. Be aware, thart free() will crash your program if the pointer is NULL. Be sure your pointer is not NULL.

You have to assume responsibility here. For all this to work, there can be no non-NULL pointers that have not been malloc'd. That after you free() a pointer, you set it tro NULL. That you never free() a pointer unless you are positive there is not another copy of it somwhere else in the program.

Errors in memory management is one opf the big reasons C++ has replaced C.

[send2aansari]

Hello again,

i am looking for a way to check if a pointer has been malloc'd.
I want to use this in a way, if the pointer has not been malloc'd to be malloc'd like that:

    if ( ! (is the pointer malloc'd))   {
        pointer = malloc(.....);
    }
 

so how can i check that ,is it possible....?
I searched the google and found no answer...

Thank you for your help....

There may be several cases . But when you are goin to allocate memory on heap then be carefully that whole responsiblity is your. How to manage it.

Let ptr is pointer which we have to chech.

case 1: If it's NULL, then no confusion just allocate memory or as you wish.

Case 2: If it's not NULL, then two cases it may be.
Case a: If it has some Valid Address then call Free
Case b: If it has some Invalid Address then make it NULL.

Remember one thing After calling function free() just make pointer to NULL manually, then you will get invalid address.


Asadullah Ansari