1 ; printf2.asm use "C" printf on char, string, int, double
2 ;
3 ; Assemble: nasm -f elf -l printf2.lst printf2.asm
4 ; Link: gcc -o printf2 printf2.o
5 ; Run: printf2
6 ; Output:
7 ;Hello world: a string of length 7 1234567 6789ABCD 5.327000e-30 -1.234568E+302
8 ;
9 ; A similar "C" program
10 ; #include <stdio.h>
11 ; int main()
12 ; {
13 ; char char1='a'; /* sample character */
14 ; char str1[]="string"; /* sample string */
15 ; int int1=1234567; /* sample integer */
16 ; int hex1=0x6789ABCD; /* sample hexadecimal */
17 ; float flt1=5.327e-30; /* sample float */
18 ; double flt2=-123.4e300; /* sample double */
19 ;
20 ; printf("Hello world: %c %s %d %X %e %E \n", /* format string for printf */
21 ; char1, str1, int1, hex1, flt1, flt2);
22 ; return 0;
23 ; }
24
25
26 extern printf ; the C function to be called
27
28 SECTION .data ; Data section
29
30 00000000 48656C6C6F20776F72- msg: db "Hello world: %c %s of length %d %d %X %e %E",10,0
31 00000009 6C643A202563202573-
32 00000012 206F66206C656E6774-
33 0000001B 682025642025642025-
34 00000024 582025652025450A00
35 ; format string for printf
36 0000002D 61 char1: db 'a' ; a character
37 0000002E 737472696E6700 str1: db "string",0 ; a C string, "string" needs 0
38 len: equ $-str1 ; len has value, not an address
39 00000035 87D61200 inta1: dd 1234567 ; integer 1234567
40 00000039 CDAB8967 hex1: dd 0x6789ABCD ; hex constant
41 0000003D BB16D80E flt1: dd 5.327e-30 ; 32-bit floating point
42 00000041 6ED768D3250BA7FE flt2: dq -123.456789e300 ; 64-bit floating point
43
44 SECTION .bss
45
46 00000000 <res 00000008> flttmp: resq 1 ; 64-bit temporary for printing flt1
47
48 SECTION .text ; Code section.
49
50 global main ; "C" main program
51 main: ; label, start of main program
52
53 00000000 D905[3D000000] fld dword [flt1] ; need to convert 32-bit to 64-bit
54 00000006 DD1D[00000000] fstp qword [flttmp] ; floating load makes 80-bit,
55 ; store as 64-bit
56 ; push last argument first
57 0000000C FF35[45000000] push dword [flt2+4] ; 64 bit floating point (bottom)
58 00000012 FF35[41000000] push dword [flt2] ; 64 bit floating point (top)
59 00000018 FF35[04000000] push dword [flttmp+4] ; 64 bit floating point (bottom)
60 0000001E FF35[00000000] push dword [flttmp] ; 64 bit floating point (top)
61 00000024 FF35[39000000] push dword [hex1] ; hex constant
62 0000002A FF35[35000000] push dword [inta1] ; integer data pass by value
63 00000030 6807000000 push dword len ; constant pass by value
64 00000035 68[2E000000] push dword str1 ; "string" pass by reference
65 0000003A FF35[2D000000] push dword [char1] ; 'a'
66 00000040 68[00000000] push dword msg ; address of format string
67 00000045 E8(00000000) call printf ; Call C function
68 0000004A 83C428 add esp, 40 ; pop stack 10*4 bytes
69
70 0000004D B800000000 mov eax, 0 ; exit code, 0=normal
71 00000052 C3 ret ; main returns to operating system