In other terms, do these functions auto-initialize memory to be ready for use? I test it out using printf to print a string. "%s" expects for a null terminated string and it seems to work so I suppose that these functions auto-initialize the bytes to \0.

However, memory is tricky and I still don't know how memory (and virtual memory) works under the hood so it may just randomly work and it may give me a segmentation fault at some point.

Does anyone knows what's going on here?

On Monday, 4 April 2022 at 07:32:00 UTC, rempas wrote:

Source code?

On Monday, 4 April 2022 at 07:39:08 UTC, Salih Dincer wrote:

Why does it matter?

import core.memory;
import core.stdc.stdio;
import core.stdc.stdlib;

extern (C) void main() {
  char* str = cast(char*)pureMalloc(23);
  str[0] = 'J';
  str[1] = 'o';
  str[2] = 'h';
  str[3] = 'n';

  printf("My name is: %s\n", str);
  exit(0);
}

Maybe, I didn't explained it properly. The example works. However, I wonder if it randomly works or if it is safe to do something like that as if the bytes have been initialized to '\0'.

On Monday, 4 April 2022 at 07:32:00 UTC, rempas wrote:

No. Neither malloc nor realloc (for which D's pure... variants are mere wrappers) are specified to initialize allocated memory. calloc, however, is - it initializes allocated block with zeroes.

On Monday, 4 April 2022 at 07:48:40 UTC, rempas wrote:

import core.memory : pureMalloc;
import core.stdc.stdio : printf;

//extern (C)
void main()
{
  int limit = 23;
  auto str = cast(char*)pureMalloc(limit);

  //while (limit--) str[limit] = '\0';
  // You need this initialize ---^
  str[0] = 'J';
  str[1] = 'o';
  str[2] = 'h';
  str[3] = 'n';

  printf("My name is: %s\n", str);
  // Wrong Output: "My name is: John�U"
}

I found no problems when using extern(). But it doesn't inspire confidence. There is obviously a memory conflict when it removes while() loop and does not use ekstern().

SDB@79

On Monday, 4 April 2022 at 09:26:13 UTC, Stanislav Blinov wrote:

Thanks, that's what I was looking for! I'll switch to calloc instead. Have a great day!