Question

code as following:

\#define CS 0x18

asm ("pushl CS"
    );

or something as an input argument:

asm("pushl %0 \n\t"

     :"m"(CS) \

    )

can the macro CS be used in the above inline asm code?

Answer 1

CS can be used in the second example, not the first.

Macros are substituted before the compiler/assembler work, so they work regardless of C or assembly.
But macros are not expanded in strings, so the first example won’t work.

If you want to make the first example work, use stringization:

#define STR1(x) #x
#define STR(x) STR1(x)
asm ("pushl " STR(CS));

This expands STR(CS) to "0x18" and concatenates it with "pushl ".