Hello all,

Does anyone know of or have experienced any problems with using new/delete
and malloc/free in the same same C++ code base? Of course, not using free()
on something you new'd.

Specially, I tend to deal with C-strings a lot and when I want to make a
copy I tend to use the strlen/new char[]/strncpy combination as in:

// s1 may be on the stack or heap it is unknown to the authour
// (i.e. returned for some library, etc.)

s1 = "Some string";

int n = strlen(s1);
char *s2 = new char[n+1];

strncpy(s2, s1, n);
s2[n] = '\0';

I would like to simplify this to simply:

s1 = "Some string"; // same conditions on s1 as above

char *s2 = strdup(s1);

However, the implementation of strdup() that I use uses malloc to duplicate
the string. Thus requiring me to use free() when I no longer want to use
s2.

So, could mixing new/delete and malloc/free in the same program cause
problems? I'm thinking issues with the heap, etc.

Thanks,

--
Chris

On 2008-02-07 09:43:56 -0500, Chris <chris@thisisnotanemailaddress.ca> said:

> // s1 may be on the stack or heap it is unknown to the authour
> // (i.e. returned for some library, etc.)
>
> s1 = "Some string";
>
> int n = strlen(s1);
> char *s2 = new char[n+1];
>
> strncpy(s2, s1, n);
> s2[n] = '\0';

strcpy will work just fine here.

>
> I would like to simplify this to simply:
>
> s1 = "Some string"; // same conditions on s1 as above
>
> char *s2 = strdup(s1);
>
> However, the implementation of strdup() that I use uses malloc to duplicate
> the string. Thus requiring me to use free() when I no longer want to use
> s2.
>
> So, could mixing new/delete and malloc/free in the same program cause
> problems? I'm thinking issues with the heap, etc.
>

No, there are no inherent problems.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)

Chris wrote:
> Does anyone know of or have experienced any problems with using
> new/delete and malloc/free in the same same C++ code base? Of course,
> not using free() on something you new'd.
>
> Specially, I tend to deal with C-strings a lot and when I want to
> make a copy I tend to use the strlen/new char[]/strncpy combination
> as in:
>
> // s1 may be on the stack or heap it is unknown to the authour
> // (i.e. returned for some library, etc.)
>
> s1 = "Some string";
>
> int n = strlen(s1);
> char *s2 = new char[n+1];
>
> strncpy(s2, s1, n);
> s2[n] = '\0';
>
> I would like to simplify this to simply:
>
> s1 = "Some string"; // same conditions on s1 as above
>
> char *s2 = strdup(s1);
>
> However, the implementation of strdup() that I use uses malloc to
> duplicate the string. Thus requiring me to use free() when I no
> longer want to use s2.

That's fine since the type is 'char'.

> So, could mixing new/delete and malloc/free in the same program cause
> problems? I'm thinking issues with the heap, etc.

Nope. Beyond the fact that 'strdup' is your own non-C++ function
which you use at your own risk, using new/delete (or new[]/delete[])
along with malloc/free is perfectly OK. Just don't use 'malloc'
for any non-POD types.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

Pete Becker wrote:

> On 2008-02-07 09:43:56 -0500, Chris <chris@thisisnotanemailaddress.ca>
> said:
>> ...
>>
>> int n = strlen(s1);
>> char *s2 = new char[n+1];
>>
>> strncpy(s2, s1, n);
>> s2[n] = '\0';
>
> strcpy will work just fine here.
>

That's true. I tend to use strncpy() out of habit.

>> ...
>>
>> So, could mixing new/delete and malloc/free in the same program cause
>> problems? I'm thinking issues with the heap, etc.
>>
>
> No, there are no inherent problems.
>

Thanks for the confirmation.

--
Chris