Why does malloc allocate a different number of bytes than requested?

by

First, Malloc makes no guarantees that two successive malloc calls return successive pointers.

Second, depending on your specific architecture, different alignment rules apply; sometimes you might ask for a single byte, but the architecture prefers allocations on 8- or 4-byte intervals.

Third, malloc needs some overhead to store how big the allocated block is, etc.

Don’t make assumptions about what malloc is doing past what the documentation says!

More Related Contents:

  1. Why does malloc initialize the values to 0 in gcc?
  2. Why do I get a C malloc assertion failure?
  3. aligned malloc() in GCC?
  4. Include source code of malloc.c in gdb?
  5. How Can I debug a C program on Linux?
  6. Why do I get different results when I dereference a pointer after freeing it?
  7. difference between and
  8. Why do I get a warning every time I use malloc?
  9. An alternative for the deprecated __malloc_hook functionality of glibc
  10. Why does the order of ‘-l’ option in gcc matter? [duplicate]
  11. Hide password input on terminal
  12. What’s the difference between a VLA and dynamic memory allocation via malloc?
  13. Trying to understand gcc option -fomit-frame-pointer
  14. Should I free memory before exit?
  15. difference between %ms and %s scanf
  16. Freaky way of allocating two-dimensional array?
  17. Function to dynamically allocate matrix
  18. How to print the address of a function?
  19. Can I rely on malloc returning NULL?
  20. Linking against older symbol version in a .so file
  21. How to initialize const in a struct in C (with malloc)
  22. GCC left shift overflow
  23. What does -D_XOPEN_SOURCE do/mean?
  24. strict aliasing in C
  25. Can I make gcc tell me when a calculation results in NaN or inf at runtime?
  26. MinGW GCC: “Unknown conversion type character ‘h'” (snprintf)
  27. Problem usage memory in C
  28. Does GCC’s __attribute__((__packed__)) retain the original ordering?
  29. How does GCC behave if passed conflicting compiler flags?
  30. How do I compile the asm generated by GCC?

Leave a Comment