String literals: pointer vs. char array

by

You can look at string literal as “a sequence of characters surrounded by double quotes”.
This string should be treated as read-only and trying to modify this memory leads to undefined behavior. It’s not necessarily stored in read only memory, and the type is char[] and not const char[], but it is still undefined behavior. The reason the type is not const is backwards compability. C didn’t have the const qualifier in the beginning. In C++, string literals have the type const char[].

So how come that you get segmentation fault?

  • The main point is that char *ptr = "string literal" makes ptr to point to the read-only memory where your string literal is stored. So when you try to access this memory: ptr[0] = 'X' (which is by the way equivalent to *(ptr + 0) = 'X'), it is a memory access violation.

On the other hand: char b[] = "string2"; allocates memory and copies string "string2" into it, thus modifying it is valid. This memory is freed when b goes out of scope.

Have a look at Literal string initializer for a character array

More Related Contents:

  1. C/SDL – Segmentation fault when program run multiple times in succession [closed]
  2. Why is this segfaulting? Can someone explain the valgrind error?
  3. Making an array using pointers in c
  4. my code does not work and I don’t know why ;-;
  5. Why do I get a segmentation fault with strcmp [closed]
  6. Crash or “segmentation fault” when data is copied/scanned/read to an uninitialized pointer
  7. String literals: Where do they go?
  8. Why is this string reversal C code causing a segmentation fault? [duplicate]
  9. How should character arrays be used as strings?
  10. “Life-time” of a string literal in C
  11. Segmentation Fault, large arrays
  12. How to split a string literal across multiple lines in C / Objective-C?
  13. Why does this code segfault on 64-bit architecture but work fine on 32-bit?
  14. segmentation fault using scanf [duplicate]
  15. Execution of printf() and Segmentation Fault
  16. What is the difference between a segmentation fault and a stack overflow?
  17. C – Segmentation Fault with strcmp?
  18. Returning pointer from a function
  19. casting char[][] to char** causes segfault?
  20. strtok segmentation fault
  21. Segmentation Fault While Creating Large Arrays in C
  22. Regular expression for a string literal in flex/lex
  23. SegFault after scanf?
  24. What is the simplest standard conform way to produce a Segfault in C?
  25. Does C support raw string literals?
  26. Pointer initialisation gives segmentation fault
  27. GCC 4.7 Source Character Encoding and Execution Character Encoding For String Literals?
  28. strlen not checking for NULL
  29. C -> sizeof string is always 8
  30. strncpy leading to segmentation fault

Leave a Comment