What does ** mean in C/C++?

Question

I am reading a c++ code and came across this line:

    mem_cMemRow ** ppMemory = (mem_cMemRow **)malloc(//size of some structs);

It seems to me that ** reserves some amount or portions of the memory but my search did not yield any good results. I appreciate any deeper and more detailed explanations on this.

It is a pointer to a pointer. Read up on double pointers. A starter here: http://www.eskimo.com/~scs/cclass/int/sx8.html — Vaibhav Desai, Apr 01 '13 at 18:17
I am sure this blog will help you to understand , what is pointer to pointer with example http://bytebeats.com/2011/08/08/pointer-to-pointer/ — abidkhan303, Apr 01 '13 at 18:21
duplicate: [What is ** in C++?](http://stackoverflow.com/q/644981/995714), [what does ** mean in C](http://stackoverflow.com/q/2893129/995714), [What is double star](http://stackoverflow.com/q/604099/995714). And [don't cast the result of `malloc` in C](http://stackoverflow.com/q/605845/995714) — phuclv, May 03 '17 at 02:55

score 4 · Accepted Answer · answered Apr 01 '13 at 18:18

4

 mem_cMemRow ** ppMemory = (mem_cMemRow **)malloc(//size of some structs)

is trying to allocate memory for ppMemry, which is a pointer to pointer type of mem_cMemRow objects. It (ppMemory) is a 2D dynamic array.

answered Apr 01 '13 at 18:18

taocp

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score 2 · Answer 2 · answered Apr 01 '13 at 18:17

2

Its a pointer to a pointer. Essentially you are creating an array of pointers to a given struct. Most likely the malloc is the sizeof a struct pointer times by some number.

answered Apr 01 '13 at 18:17

Goz

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score 1 · Answer 3 · answered Apr 01 '13 at 18:17

1

One star means a pointer. Two stars mean a pointer to a pointer. So, ppMemory is a pointer to a pointer to a mem_cMemRow.

answered Apr 01 '13 at 18:17

Alexey Frunze

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What does ** mean in C/C++?

3 Answers3