Reusing pointers

[Edelweiss]

Hi I have a situation here in which i malloc a char_t* pt and free it. If I want to reuse this pt and malloc it of another size. Will there be any risk involved?

[laserlight]

Yes, there is risk involved. The further apart the second malloc is from the first free, the higher the chance you might blunder (though setting the pointer to be a null pointer after the free may mitigate potential blunders). But if you talk about correctness rather than risk, then indeed it can be done correctly.

[CommonTater]

Hi I have a situation here in which i malloc a char_t* pt and free it. If I want to reuse this pt and malloc it of another size. Will there be any risk involved?

One tactic you might explore to mitigate some of the risk is the creation of intermediate scopes in your programs...

// lots of code

{                                    <-- scope starts here
   char *pchar = malloc(100 * sizeof(char);
   // do stuff with pchar
   free(pchar);
}                                    <-- scope ends here pchar is destroyed

// more code

This will let you create variables use them and forget about them on the fly.

Here's a live code example... (it's Windows API code, but I think you'll get the idea)

void GoButton( void )
  {  
     WCHAR password[25];

    { 
      WORD port;
      GetWindowText(Wind[4],password,24);
      port = _wtoi(password); 
      InitNetwork(port); 
     }
    
    { 
      DWORD pcode;
      WCHAR ltxt[MAX_LOGLINE];
      GetWindowText(Wind[2],password,24);
      pcode = SetPassCode(password);
      if (!pcode)
       { 
          lstrcpy(ltxt,L"Password improperly entered");
          AddToLog(L"Error",ltxt); 
       } 
     }

    EnableWindow(Wind[2],0);
    EnableWindow(Wind[4],0);
    EnableWindow(Wind[5],0); 
}

[AndrewHunter]

Haha.....nice comment. Don't give in Tater, stay strong!

[CommonTater]

Haha.....nice comment. Don't give in Tater, stay strong!

As they say... Iligitimi non carborundum ...

[whiteflags]

Illigitimate carborator?

[CommonTater]

Illigitimate carborator?

Oh boy... sharp as a tack on C Code ... not so good with humour, I see...

It's an old engineering joke in faux latin... Iligitimi = Illigitimate = Child born out of wedlock. Carborundum is a brand name for grindstones. Non = negative, no, not...

Thus ... "Don't let the b**tards wear you down"

[slingerland3g]

If you can get around freeing the pointer, you could use realloc(), but check its returns for any pitfalls.
realloc

[CommonTater]

If you can get around freeing the pointer, you could use realloc(), but check its returns for any pitfalls.
realloc

Except that realloc() retains whatever content was already in the buffer... I doubt that's what the OP wants...

[slingerland3g]

Except that realloc() retains whatever content was already in the buffer... I doubt that's what the OP wants...

Ah, very true!