3.5 Pseudo-Op Examples

3.5.1 Example 1: Binding to C Variables

This example shows how to use the following pseudo-ops to specify the bindings of variables in C:

.common, .global, .local, .weak

The following C definitions/declarations:

    int foo1 = 1;
#pragma weak foo2 = foo1
    static int foo3;
    static int foo4 = 2;

can be translated into the following assembly code.

Example 3-1 Using Pseudo-ops to Specify C Variable Bindings

    .pushsection    ".data"

    .global   foo1    ! int foo1 = 1
    .align    4
foo1:
    .word  0x1
    .type  foo1,#object            ! foo1 is of type data object,
    .size  foo1,4                ! with size = 4 bytes
       
    .weak  foo2            ! #pragma weak foo2 = foo1
    foo2 = foo1

    .local  foo3            ! static int foo3
    .common  foo3,4,4

    .align  4            ! static int foo4 = 2
   foo4:
    .word  0x2
    .type  foo4,#object
    .size  foo4,4

    .popsection

3.5.2 Example 2: Generating Ident Strings

This example shows how to use the pseudo-op .ident to generate a string in the .comment section of the object file for identification purposes.

.ident            "myprog: This is an example of an ident string"

3.5.3 Example 3: Data Alignment, Size, Scope, and Type

The pseudo-ops shown in this example are .align, .global, .type, and .size.

The following C subroutine:

int sum(a, b)
    int a, b;
{
    return(a + b);
}

can be translated into the following assembly code:

    .section  ".text"

    .global  sum

    .align  4

sum:             
    retl
    add  %o0,%o1,%o0            ! (a + b) is done in the

                            ! delay slot of retl

    .type  sum,#function            ! sum is of type function
    .size  sum,.-sum            ! size of sum is the diff

                            ! of current location
                            ! counter and the initial
                            ! definition of sum      

3.5.4 Example 4: “Hello World”

The pseudo-ops shown in this example are .section, .ascii, and .align. The example calls the printf function to output the string "hello world".

    .section            ".data1"
    .align        4
.L16:
    .ascii   "hello world\n\0"

    .section  ".text"
    .global  main
main:
    save  %sp,-96,%sp
    set  .L16,%o0
    call  printf,1
    nop
    restore