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Is it safe to delete a NULL pointer?

Is it safe to delete a NULL pointer?

And is it a good coding style?

Allowed memory size of 33554432 bytes exhausted (tried to allocate 43148176 bytes) in php

This error message is being presented, any suggestions?

Allowed memory size of 33554432 bytes exhausted (tried to allocate 43148176 bytes) in php

What is the difference between new/delete and malloc/free?

What is the difference between new/delete and malloc/free?

Related (duplicate?): In what cases do I use malloc vs new?

What uses are there for "placement new"?

Has anyone here ever used C++'s "placement new"? If so, what for? It looks to me like it would only be useful on memory-mapped hardware.

How to allocate aligned memory only using the standard library?

I just finished a test as part of a job interview, and one question stumped me - even using google for reference. I'd like to see what the stackoverflow crew can do with it:

The “memset_16aligned” function requires a 16byte aligned pointer passed to it, or it will crash.

a) How would you allocate 1024 bytes of memory, and align it to a 16 byte boundary?
b) Free the memory after the memset_16aligned has executed.

{

   void *mem;

   void *ptr;

   // answer a) here

   memset_16aligned(ptr, 0, 1024);

   // answer b) here

}

How do malloc() and free() work?

I want to know how malloc and free work.

int main()
{

    unsigned char *p = (unsigned char*)malloc(4*sizeof(unsigned char));
    memset(p,0,4);
    strcpy((char*)p,"abcdabcd"); // **deliberately storing 8bytes**
    cout << p;
    free(p); // Obvious Crash, but I need how it works and why crash.
    cout << p;
    return 0;
}

I would be really grateful if the answer is in depth at memory level, if it's possible.

How do I discover memory usage of my application in Android?

How can I find the memory used on my Android application, programmatically?

I hope there is a way to do it. Plus, how do I get the free memory of the phone too?

In what cases do I use malloc vs new?

I see in C++ there are multiple ways to allocate and free data and I understand that when you call malloc you should call free and when you use the new operator you should pair with delete and it is a mistake to mix the two (e.g. Calling free() on something that was created with the new operator), but I'm not clear on when I should use malloc/ free and when I should use new/ delete in my real world programs.

If you're a C++ expert, please let me know any rules of thumb or conventions you follow in this regard.

C++ new int[0] -- will it allocate memory?

A simple test app:

cout << new int[0] << endl;

outputs:

0x876c0b8

So it looks like it works. What does the standard say about this? Is it always legal to "allocate" empty block of memory?

Peak memory usage of a linux/unix process

Is there a tool that will run a command-line and report how much RAM was used total?

I'm imagining something analogous to /usr/bin/time

Does using "new" on a struct allocate it on the heap or stack?

When you create an instance of a class with the new operator, memory gets allocated on the heap. When you create an instance of a struct with the new operator where does the memory get allocated, on the heap or on the stack ?

@property and retain, assign, copy, nonatomic in Objective-C

As someone that's new to Objective-C can someone give me an overview of the retain, assign, copy and any others I'm missing, that follow the @property directive? What are they doing and why would I want to use one over another?

Which Python memory profiler is recommended? [closed]

I want to know the memory usage of my Python application and specifically want to know what code blocks/portions or objects are consuming most memory. Google search shows a commercial one is Python Memory Validator.

And open source ones are PySizer and Heapy.

I haven't tried anyone, so I wanted to know which one is the best considering:

1. Gives most details.

2. I have to do least or no changes to my code.

What and where are the stack and heap?

Programming language books explain that value types are created on the stack, and reference types are created on the heap, without explaining what these two things are. I haven't read a clear explanation of this. I understand what a stack is, but where and what are they (physically in a real computer's memory)?

• To what extent are they controlled by the OS or language runtime?
• What is their scope?
• What determines the size of each of them?
• What makes one faster?

Why is my program slow when looping over exactly 8192 elements?

Here is the extract from the program in question. The matrix img[][] has the size SIZE×SIZE, and is initialized at:

img[j][i] = 2 * j + i

Then, you make a matrix res[][], and each field in here is made to be the average of the 9 fields around it in the img matrix. The border is left at 0 for simplicity.

for(i=1;i<SIZE-1;i++) 
    for(j=1;j<SIZE-1;j++) {
        res[j][i]=0;
        for(k=-1;k<2;k++) 
            for(l=-1;l<2;l++) 
                res[j][i] += img[j+l][i+k];
        res[j][i] /= 9;
}

That's all there's to the program. For completeness' sake, here is what comes before. No code comes after. As you can see, it's just initialization.

#define SIZE 8192
float img[SIZE][SIZE]; // input image
float res[SIZE][SIZE]; //result of mean filter
int i,j,k,l;
for(i=0;i<SIZE;i++) 
    for(j=0;j<SIZE;j++) 
        img[j][i] = (2*j+i)%8196;

Basically, this program is slow when SIZE is a multiple of 2048, e.g. the execution times:

SIZE = 8191: 3.44 secs
SIZE = 8192: 7.20 secs
SIZE = 8193: 3.18 secs

The compiler is GCC. From what I know, this is because of memory management, but I don't really know too much about that subject, which is why I'm asking here.

Also how to fix this would be nice, but if someone could explain these execution times I'd already be happy enough.

I already know of malloc/free, but the problem is not amount of memory used, it's merely execution time, so I don't know how that would help.