memcpy() vs memmove()

by

I’m not entirely surprised that your example exhibits no strange behaviour. Try copying str1 to str1+2 instead and see what happens then. (May not actually make a difference, depends on compiler/libraries.)

In general, memcpy is implemented in a simple (but fast) manner. Simplistically, it just loops over the data (in order), copying from one location to the other. This can result in the source being overwritten while it’s being read.

Memmove does more work to ensure it handles the overlap correctly.

EDIT:

(Unfortunately, I can’t find decent examples, but these will do). Contrast the memcpy and memmove implementations shown here. memcpy just loops, while memmove performs a test to determine which direction to loop in to avoid corrupting the data. These implementations are rather simple. Most high-performance implementations are more complicated (involving copying word-size blocks at a time rather than bytes).

More Related Contents:

  1. What is the difference between memmove and memcpy?
  2. Is it guaranteed to be safe to perform memcpy(0,0,0)?
  3. memcpy vs assignment in C
  4. faster alternative to memcpy?
  5. Very fast memcpy for image processing?
  6. Will memcpy or memmove cause problems copying classes?
  7. Can I call memcpy() and memmove() with “number of bytes” set to zero?
  8. Can I free pointer address without malloc?
  9. can anyone explain the output of the following code in c [closed]
  10. What is the difference between char s[] and char *s?
  11. How would one write object-oriented code in C? [closed]
  12. Disadvantages of scanf
  13. enum to string in modern C++11 / C++14 / C++17 and future C++20
  14. Reading a line using scanf() not good?
  15. Tools to get a pictorial function call graph of code [closed]
  16. Rand Implementation
  17. What does malloc(0) return? [duplicate]
  18. Difference between signed / unsigned char [duplicate]
  19. Undefined reference to `initscr’ Ncurses
  20. Efficient 4×4 matrix vector multiplication with SSE: horizontal add and dot product – what’s the point?
  21. How to extract the decimal part from a floating point number in C?
  22. Why does open() create my file with the wrong permissions?
  23. Determining sprintf buffer size – what’s the standard?
  24. Optimized matrix multiplication in C
  25. Does C99 guarantee that arrays are contiguous?
  26. Why we must initialize a variable before using it? [duplicate]
  27. Why declare a struct that only contains an array in C?
  28. Dynamic method dispatching in C
  29. Assign multiple values to array in C
  30. Is there a way to convert from UTF8 to ISO-8859-1?

Leave a Comment