CODEWITHSUNDEEP
assemblyx86inline-assemblygnu-assembler
Weve
Weve

Reputation: 31

Within __asm__, what does "$variable" mean?

int context(){"\
       movl $0, %eax;\
       push $xxxxx;\
       push $0;\
       push %eax;\
       ...........
       xxxxx : leave;\
       ret;");
}

I'm very beginner.

At above source code, I couldn't understand the meaning of "$xxxxx". I thought symbol '$' is only come front of constant.

Moreover, I have never seen last two lines. I know about leave and ret instruction, but "xxxxx :" form is so unfamiliar. I can't find the example looks like it.

Upvotes: 0

Views: 157

Answers (1)

Michael Burr
Michael Burr

Reputation: 340198

The $ prefix signals an immediate operand in the GNU assembler's AT&T syntax. See https://sourceware.org/binutils/docs/as/i386_002dVariations.html#i386_002dVariations:

AT&T immediate operands are preceded by '$';

The line:

xxxxx : leave;

uses xxxxx as a label (https://sourceware.org/binutils/docs/as/Labels.html#Labels).

A label is written as a symbol immediately followed by a colon `:'

In the case you're wondering about, the value of the label xxxxx is the immediate operand.

Upvotes: 1

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