What does “pointer being freed was not allocated” mean exactly?

Only pointers returned by calls to malloc(), realloc() or calloc() can be passed to free() (dynamically allocated memory on the heap). From section 7.20.3.2 The free function of C99 standard:

The free function causes the space pointed to by ptr to be deallocated, that is, made available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if the argument does not match a pointer earlier returned by the calloc, malloc, or realloc function, or if the space has been deallocated by a call to free or realloc, the behavior is undefined.

In the posted code, str is not dynamically allocated but is allocated on the stack and is automatically released when it goes out of scope and does not need to be free()d.

Related Posts:

  1. How big can a 64 bit unsigned integer be?
  2. warning: implicit declaration of function
  3. What is *(uint32_t*)?
  4. Why should we typedef a struct so often in C?
  5. What is a string of hexadecimal digits?
  6. What is the difference between ++i and i++?
  7. Stack smashing detected
  8. Stack smashing detected
  9. How do I determine the size of my array in C?
  10. Why am I getting “void value not ignored as it ought to be”?
  11. Pointer Arithmetic
  12. Openssl : error “self signed certificate in certificate chain”
  13. What is the difference between C and embedded C?
  14. How do I create an array of strings in C?
  15. Difference between malloc and calloc?
  16. How do function pointers in C work?
  17. segmentation fault : 11
  18. What are .a and .so files?
  19. So what does “return 0” actually mean?
  20. “Expected expression before ‘ { ‘ token”
  21. How to generate a random int in C?
  22. C pointers and arrays: [Warning] assignment makes pointer from integer without a cast
  23. warning: assignment makes integer from pointer without a cast
  24. How to print the array?
  25. How to solve the error: assignment to expression with array type
  26. segmentation fault : 11
  27. Why use bzero over memset?
  28. What does “1e” mean?
  29. how to use uint64_t in C [duplicate]
  30. How do I solve the following errors: “Undefined reference to WinMain”, “[Error] Id returned 1 exit status”?
  31. Warning comparison between pointer and integer
  32. How do I properly compare strings in C?
  33. Connect: Socket operation on non-socket
  34. How to correctly use the extern keyword in C
  35. How do we check if a pointer is NULL pointer?
  36. how to use wait in C
  37. what is the meaning of == sign?
  38. How do I calculate MB/s & MiB/s?
  39. How to create my own header file in c++?
  40. ARM Assembler – How do I use CMP, BLT and BGT?
  41. In C programming, what is `undefined reference`error, when compiling?
  42. Invalid read of size 8 – Valgrind + C
  43. warning: incompatible implicit declaration of built-in function ‘xyz’
  44. strcpy vs strdup
  45. double free or corruption (fasttop)
  46. Warning comparison between pointer and integer in C language
  47. error: expected declaration or statement at end of input in c
  48. Why do I get clang: error: linker command failed with exit code 1?
  49. Difference between scanf() and fgets()
  50. Return char[]/string from a function [duplicate]
  51. How to convert integer to char in C?
  52. Is there a printf converter to print in binary format?
  53. Program received signal SIGPIPE, Broken pipe
  54. Difference between char* and const char*?
  55. How to read from stdin with fgets()?
  56. Output single character in C
  57. Does connect() block for TCP socket?
  58. Converting a C program to MIPS
  59. Why am I getting “array initializer must be an initializer list or string literal”?
  60. what is the unsigned datatype?
  61. C: linker command failed with exit code 1
  62. #31 expression must have integral type
  63. How do you pass a function as a parameter in C?
  64. What’s the equivalent of new/delete of C++ in C?
  65. sizeof float (3.0) vs (3.0f)
  66. How to trigger SIGUSR1 and SIGUSR2?
  67. What does “%.*s” mean in printf?
  68. Display value found at given address gdb
  69. Does C have a “foreach” loop construct?
  70. What is a bus error? Is it different from a segmentation fault?
  71. Array definition – Expression must have a constant value
  72. Constant pointer vs Pointer to constant
  73. What is the cause of flexible array member not at end of struct error?
  74. Variable warning set but not used
  75. Reversing a string in C
  76. When a number is written as 0x00… what does the x mean
  77. Expected declaration specifier error in function
  78. How can I get argv[] as int?
  79. Why I do get “Cannot find bound of current function” when I overwrite the ret address of a vulnerable program?
  80. valgrind – Address —- is 0 bytes after a block of size 8 alloc’d
  81. Writing binary number system in C code
  82. Convert char array to string use C
  83. warning: passing argument ’from incompatible pointer type [enabled by default]’
  84. Return a `struct` from a function in C
  85. How does one represent the empty char?
  86. Removing trailing newline character from fgets() input
  87. “Multiple definition”, “first defined here” errors
  88. how use EOF stdin in C
  89. Execution of printf() and Segmentation Fault
  90. How does the strtok function in C work? [duplicate]
  91. Allocating char array using malloc
  92. Implementation of strtok() function
  93. switch case: error: case label does not reduce to an integer constant
  94. warning: incompatible implicit declaration of built-in function ‘printf’ [enabled by default]
  95. warning: return makes pointer from integer without a cast but returns integer as desired
  96. Reaching EOF with fgets
  97. The difference between char * and char[] [duplicate]
  98. How to clear input buffer in C?
  99. Compiler warning – suggest parentheses around assignment used as truth value
  100. error: `itoa` was not declared in this scope

Leave a Comment