Invalid pointer error on invoking free() after malloc in C

I am doing very basic dynamic allocation practice in C and I came across this issue: when I am trying to call free() with the pointer returned by malloc(), I am getting Invalid pointer error during run time.

When I remove free() from code, it works fine. The pointer that I am using is not modified anyhow after returned by malloc (except the casting). So that rules out some suggestion I found online. Below is my code:

#include <stdio.h>
#include <stdlib.h>

int main() {
        int num = 0;
        //printf("Enter a number: ");
        //scanf("%d", &num);
        char* p = (char*)malloc(16*sizeof(char));
        printf("%p", p);
        if(p) {
                p = "mark";
                printf("\n%s\n", p);
                free(p); //when removed no error
        }
        return 0;
}

Following is the error message:

0xa26010
mark
*** Error in `./a.out': free(): invalid pointer: 0x00000000004006b7 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x777e5)[0x7fa968aed7e5]
/lib/x86_64-linux-gnu/libc.so.6(+0x8037a)[0x7fa968af637a]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7fa968afa53c]
./a.out[0x40061a]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7fa968a96830]
./a.out[0x4004e9]
======= Memory map: ========
00400000-00401000 r-xp 00000000 08:03 6815746                            /home/kushal/Documents/GATE/prac_C/a.out
00600000-00601000 r--p 00000000 08:03 6815746                            /home/kushal/Documents/GATE/prac_C/a.out
00601000-00602000 rw-p 00001000 08:03 6815746                            /home/kushal/Documents/GATE/prac_C/a.out
00a26000-00a47000 rw-p 00000000 00:00 0                                  [heap]
7fa964000000-7fa964021000 rw-p 00000000 00:00 0 
7fa964021000-7fa968000000 ---p 00000000 00:00 0 
7fa968860000-7fa968876000 r-xp 00000000 08:03 39719295                   /lib/x86_64-linux-gnu/libgcc_s.so.1
7fa968876000-7fa968a75000 ---p 00016000 08:03 39719295                   /lib/x86_64-linux-gnu/libgcc_s.so.1
7fa968a75000-7fa968a76000 rw-p 00015000 08:03 39719295                   /lib/x86_64-linux-gnu/libgcc_s.so.1
7fa968a76000-7fa968c36000 r-xp 00000000 08:03 39714902                   /lib/x86_64-linux-gnu/libc-2.23.so
7fa968c36000-7fa968e36000 ---p 001c0000 08:03 39714902                   /lib/x86_64-linux-gnu/libc-2.23.so
7fa968e36000-7fa968e3a000 r--p 001c0000 08:03 39714902                   /lib/x86_64-linux-gnu/libc-2.23.so
7fa968e3a000-7fa968e3c000 rw-p 001c4000 08:03 39714902                   /lib/x86_64-linux-gnu/libc-2.23.so
7fa968e3c000-7fa968e40000 rw-p 00000000 00:00 0 
7fa968e40000-7fa968e66000 r-xp 00000000 08:03 39714844                   /lib/x86_64-linux-gnu/ld-2.23.so
7fa969046000-7fa969049000 rw-p 00000000 00:00 0 
7fa969064000-7fa969065000 rw-p 00000000 00:00 0 
7fa969065000-7fa969066000 r--p 00025000 08:03 39714844                   /lib/x86_64-linux-gnu/ld-2.23.so
7fa969066000-7fa969067000 rw-p 00026000 08:03 39714844                   /lib/x86_64-linux-gnu/ld-2.23.so
7fa969067000-7fa969068000 rw-p 00000000 00:00 0 
7ffcf8e4b000-7ffcf8e6c000 rw-p 00000000 00:00 0                          [stack]
7ffcf8f1d000-7ffcf8f20000 r--p 00000000 00:00 0                          [vvar]
7ffcf8f20000-7ffcf8f22000 r-xp 00000000 00:00 0                          [vdso]

Related Posts:

  1. Pointer Arithmetic
  2. char *array and char array[]
  3. C pointers and arrays: [Warning] assignment makes pointer from integer without a cast
  4. Difference between char* and const char*?
  5. #31 expression must have integral type
  6. How do you pass a function as a parameter in C?
  7. expression must have integral type
  8. C free(): invalid pointer
  9. What’s wrong with my code? What is argv[1]?
  10. Valgrind: Invalid read of size 1
  11. Constant pointer vs Pointer to constant
  12. Reversing a string in C
  13. Warning: return from incompatible pointer type in C
  14. strcmp giving segmentation fault
  15. Why am I getting this error: “data definition has no type or storage class”?
  16. warning: passing argument ’from incompatible pointer type [enabled by default]’
  17. char pointers: invalid conversion from ‘char*’ to ‘char’?
  18. What is the difference between char array and char pointer in C?
  19. double free or corruption (!prev) error in c program
  20. typedef struct pointer definition
  21. Dereference void pointer
  22. The difference between char * and char[] [duplicate]
  23. lvalue required as increment operand
  24. The difference between n++ and ++n at the end of a while loop? (ANSI C)
  25. Working on code to calculate cosine with factorial sum
  26. warning: implicit declaration of function
  27. What exactly is the difference between “pass by reference” in C and in C++?
  28. What does “collect2: error: ld returned 1 exit status” mean?
  29. How to convert an int to string in C?
  30. Floating point exception (core dumped)
  31. what is the difference between uint16_t and unsigned short int incase of 64 bit processor?
  32. Correct format specifier for double in printf
  33. How to convert a string to integer in C?
  34. What is the behavior of integer division?
  35. Awesomium sdk download
  36. Bad File Descriptor with Linux Socket write() Bad File Descriptor C
  37. What is the difference between char s[] and char *s?
  38. Reading from file using read() function
  39. What is the difference between ++i and i++?
  40. warning: assignment makes integer from pointer without a cast
  41. munmap_chunk(): invalid pointer
  42. printf() formatting for hexadecimal
  43. The importance of c enumeration (typedef enum) [duplicate]
  44. Error “initializer element is not constant” when trying to initialize variable with const
  45. Cannot assign requested address – possible causes?
  46. need help understanding the movzbl call in this function
  47. What is the difference between read and pread in unix?
  48. What does “control reaches end of non-void function” mean?
  49. connect Error: “No route to host”
  50. warning: implicit declaration of function
  51. C dynamically growing array
  52. How to replicate vector in c?
  53. Why do I get an assertion failure?
  54. Difference between int32, int, int32_t, int8 and int8_t
  55. C compile error: “Variable-sized object may not be initialized”
  56. lvalue required as left operand of assignment
  57. how to convert negative hexadecimal to decimal
  58. In C, how should I read a text file and print all strings
  59. What does “Size in TCHARs” means?
  60. Python ? (conditional/ternary) operator for assignments
  61. What’s the difference between a file descriptor and file pointer?
  62. return makes integer from pointer without a cast [-Wint-conversion] return candidate
  63. How do you pass a function as a parameter in C?
  64. Math constant PI value in C
  65. Cygwin – Makefile-error: recipe for target `main.o’ failed
  66. How do you pass a function as a parameter in C?
  67. Why am I getting “undefined reference to sqrt” error even though I include math.h header?
  68. Why am I getting “undefined reference to sqrt” error even though I include math.h header?
  69. How can I use an array of function pointers?
  70. When and why to use malloc?
  71. C compile error: Id returned 1 exit status
  72. How do I concatenate const/literal strings in C?
  73. Efficient way to find task_struct by pid
  74. Why am I getting this memory access error ‘double free or corruption’?
  75. size of struct in C
  76. How can one print a size_t variable portably using the printf family?
  77. How to make sense of modulo in c
  78. “No such file or directory” error in CodeBlocks
  79. Uninitialized value was created by a heap allocation
  80. Makefile:1: *** missing separator. Stop
  81. Why do I get “cast from pointer to integer of different size” error?
  82. xorl %eax – Instruction set architecture in IA-32
  83. Excess elements of scalar initializer for pointer to array of ints
  84. Two or more data types in declaration specifiers error
  85. ‘sprintf’: double precision in C
  86. C printing bits
  87. Casting a pointer to an int
  88. PTHREAD_MUTEX_INITIALIZER vs pthread_mutex_init ( &mutex, param)
  89. How to concatenate string and int in C?
  90. execvp: bad address error
  91. How detect malloc failure?
  92. A Simple, 2d cross-platform graphics library for c or c++?
  93. Removing last character in C
  94. Difference between char *argv[] and char **argv for the second argument to main()
  95. error: ISO C forbids nested functions – What’s wrong?
  96. Use of flag in c?
  97. Carriage return in C?
  98. Difference between “while” loop and “do while” loop
  99. Swapping 2 Bytes of Integer
  100. GDB no such file or directory

Leave a Comment