need help understanding the movzbl call in this function

A corresponding C function would be something like

char fn(char * string, int index)
{
    return string[index];
}

Specifically, the movzbl instruction fetches the byte stored at the sum of the two parameters, zero pads it, and stores it into eax. The movsbl instruction takes the lowest byte of eax, sign extends it, and stores the result back in eax.

Related Posts:

  1. Display value found at given address gdb
  2. xorl %eax – Instruction set architecture in IA-32
  3. ARM Assembler – How do I use CMP, BLT and BGT?
  4. X86 assembly – Handling the IDIV instruction
  5. GDB no such file or directory
  6. What does the LEAL assembly instruction do?
  7. How big can a 64 bit unsigned integer be?
  8. What’s the purpose of the LEA instruction?
  9. The difference between n++ and ++n at the end of a while loop? (ANSI C)
  10. Implementing Taylor Series for sine and cosine in C
  11. Working on code to calculate cosine with factorial sum
  12. How to use execvp()
  13. How to use execvp() to execute a command
  14. How does strtok() split the string into tokens in C?
  15. warning: implicit declaration of function
  16. warning: implicit declaration of function
  17. What is *(uint32_t*)?
  18. pthread_join() and pthread_exit()
  19. what is Segmentation fault (core dumped)? [duplicate]
  20. What causes a segmentation fault (core dump) to occur in C?
  21. uint8_t vs unsigned char
  22. How to use symbols of extended ASCII table in C?
  23. Two questions about basic C programs
  24. What is the difference between ++i and i++?
  25. Using boolean values in C
  26. What does “collect2: error: ld returned 1 exit status” mean?
  27. How to convert an int to string in C?
  28. typedef struct vs struct definitions [duplicate]
  29. How to print in C
  30. Why should we typedef a struct so often in C?
  31. What is a string of hexadecimal digits?
  32. Why should we typedef a struct so often in C?
  33. What exactly is the difference between “pass by reference” in C and in C++?
  34. What is the difference between ++i and i++?
  35. What can be the reasons of connection refused errors?
  36. What does “collect2: error: ld returned 1 exit status” mean?
  37. How to convert an int to string in C?
  38. typedef struct vs struct definitions [duplicate]
  39. What is newline character — ‘\n’
  40. Why does ENOENT mean “No such file or directory”?
  41. What does the question mark character (‘?’) mean?
  42. Cannot figure out how to use getchar(); in C
  43. Floating point exception (core dumped)
  44. Undefined reference to pthread_create in Linux
  45. what is the difference between uint16_t and unsigned short int incase of 64 bit processor?
  46. makefile:4: *** missing separator. Stop
  47. Stack smashing detected
  48. Why am I getting “void value not ignored as it ought to be”?
  49. Correct format specifier for double in printf
  50. Stack smashing detected
  51. How do I determine the size of my array in C?
  52. Why am I getting “void value not ignored as it ought to be”?
  53. Pointer Arithmetic
  54. dereferencing pointer to incomplete type
  55. 1 = false and 0 = true?
  56. c stack smashing detected
  57. Openssl : error “self signed certificate in certificate chain”
  58. How to convert a string to integer in C?
  59. What is the difference between C and embedded C?
  60. Get a substring of a char* [duplicate]
  61. char *array and char array[]
  62. How do I create an array of strings in C?
  63. Understanding cmp instruction
  64. Undefined reference to pthread_create
  65. What is the behavior of integer division?
  66. Convert char to int in C and C++
  67. Get a substring of a char*
  68. Difference between malloc and calloc?
  69. What is Bit Masking?
  70. How do function pointers in C work?
  71. Expression must be a modifiable L-value
  72. What causes the Broken Pipe Error?
  73. segmentation fault : 11
  74. Strings and character with printf
  75. Awesomium sdk download
  76. What is EOF in the C programming language?
  77. What are .a and .so files?
  78. Why does the terminal show “^[[A” “^[[B” “^[[C” “^[[D” when pressing the arrow keys in Ubuntu?
  79. So what does “return 0” actually mean?
  80. “Expected expression before ‘ { ‘ token”
  81. Bad File Descriptor with Linux Socket write() Bad File Descriptor C
  82. How to generate a random int in C?
  83. How do I use valgrind to find memory leaks?
  84. C pointers and arrays: [Warning] assignment makes pointer from integer without a cast
  85. Why is the gets function so dangerous that it should not be used?
  86. Write to .txt file?
  87. What is the difference between char s[] and char *s?
  88. warning: assignment makes integer from pointer without a cast
  89. How to print the array?
  90. How to solve the error: assignment to expression with array type
  91. segmentation fault : 11
  92. Why use bzero over memset?
  93. Reading from file using read() function
  94. What is the difference between ++i and i++?
  95. What does “collect2: error: ld returned 1 exit status” mean?
  96. What does “1e” mean?
  97. warning: assignment makes integer from pointer without a cast
  98. munmap_chunk(): invalid pointer
  99. printf() formatting for hexadecimal
  100. Warning comparison between pointer and integer

Leave a Comment