malloc() resulting in a SegFault?!

master5001 · 09-17-2008, 12:29 PM

Fair enough.

Example:

Code:

inline template<typename AnyTypeYouWant>
AnyTypeYouWant *malloc_ptr(size_t x)
{
  return reinterpret_cast<AnyTypeYouWant *>(malloc(size_t * sizeof(AnyTypeYouWant)));
}

inline template<typename AnyTypeYouWant>
AnyTypeYouWant &malloc_ref(size_t x)
{
  AnyTypeYouWant *ptr = malloc_ptr(x);

  if(!ptr)
  {
    throw std::bad_alloc("Null reference");
  }

  return *ptr;
}

Alright, now everyone is happy. I have added a healthy level of sarcasm to a few lines of code (which always brightens my day). I still say you are just a quick one. Of course, your name is laserlight, I should expect you to be swift.

rags_to_riches · 09-17-2008, 12:39 PM

Quote:

Originally Posted by laserlight

Note that that FAQ pertains to C. This is C++, so casting the return value of malloc() is not bad style, but rather is required.

DOH! My bad! Of course, I agree that one should not be using malloc in a C++ environment any way

master5001 · 09-17-2008, 12:46 PM

Placement new... But then again, who likes to explicitly call a destructor?

Example:

Code:

int *x = new(malloc(sizeof(*x))) int;

// At which point this line is perfectly acceptable
free(x);

samGwilliam · 09-18-2008, 07:12 AM

Quote:

Originally Posted by master5001

Note: That is for the benefit of the OP and other people with similar misconceptions, not matsp who is well aware of these facts. It is important that people know by design you should not mix and match your C and C++ dynamic memory allocations.

I must admit that my coding style is a hybrid of C and C++. I always use new and delete, but I've never bothered with templates or try/catch and I pass by reference the C way. I'm still in the habit of using the .h when including too.

Elysia · 09-18-2008, 11:16 AM

It doesn't really matter what the contents is in a header. The extension is optional. You can use .h in C++, as well as C. I wouldn't say it's wrong or bad practice.
And especially in C++, I would avoid saying "passing by reference" if you aren't actually doing it (ie passing by pointer), because in C++ there are references and pointers.

But you should really try out templates, at the very least. Very powerful stuff right there.

**laserlight** · 09-18-2008, 11:20 AM

Quote:

Originally Posted by Elysia

It doesn't really matter what the contents is in a header. The extension is optional. You can use .h in C++, as well as C. I wouldn't say it's wrong or bad practice.

I suspect that samGwilliam is referring to a habit of including the C standard headers instead of their C++ versions.

Elysia · 09-18-2008, 11:24 AM

Oh. Maybe you're right, now that I do think of it...

09-17-2008, 12:29 PM	#16
master5001 Banned Join Date: Aug 2001 Location: Visalia, CA, USA Posts: 3,699	Fair enough. Example: Code: inline template<typename AnyTypeYouWant> AnyTypeYouWant malloc_ptr(size_t x) { return reinterpret_cast<AnyTypeYouWant >(malloc(size_t * sizeof(AnyTypeYouWant))); } inline template<typename AnyTypeYouWant> AnyTypeYouWant &malloc_ref(size_t x) { AnyTypeYouWant ptr = malloc_ptr(x); if(!ptr) { throw std::bad_alloc("Null reference"); } return ptr; } Alright, now everyone is happy. I have added a healthy level of sarcasm to a few lines of code (which always brightens my day). I still say you are just a quick one. Of course, your name is laserlight, I should expect you to be swift.
master5001 is offline

09-17-2008, 12:46 PM	#18
master5001 Banned Join Date: Aug 2001 Location: Visalia, CA, USA Posts: 3,699	Placement new... But then again, who likes to explicitly call a destructor? Example: Code: int x = new(malloc(sizeof(x))) int; // At which point this line is perfectly acceptable free(x);
master5001 is offline

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