Assembler Enbedded C Program

bigapple · 08-02-2005, 03:26 AM

hi, all
I have seen some code like this:

Code:

asm volatile (							      \
    LOADARGS_##nr							      \
    "movl %1, %%eax\n\t"						      \
    "int _0x81\n\t"							      \
    RESTOREARGS_##nr							      \
    : "=a" (resultvar)							      \
    : "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc");		      \
    if (resultvar >= 0xfffff001)					      \
      {									      \
	errno= (-resultvar);					      \
	resultvar = 0xffffffff;						      \
      }									      \
    (int) resultvar; })

I konw there is some assembler language embedded in this program,and the key words "asm volatile" tell the compiler "following is assembler language", So I want to konw ,if I want to compile such kind of C program, which argument should be add in gcc command.
if anyone have the experience of write/compile such kind of program,please give me a simple demo,and show the procedure of how to compile it and run it. It will be very helpful to me ,thnx a lot. and you can give a link to a web site

lowpro2k3 · 08-02-2005, 12:08 PM

What happens when you just try and run the compiler with default arguments?

gcc -o program program.c

bigapple · 08-02-2005, 09:50 PM

ok ,I see,the reason that I can't compile the program is my gcc version is 2.9. and it can't compile the assembler embedded C program, so I have update the gcc to newest,and I can compile the program successful with the default arguments.
if you want to use the "asm" as a varible in you program ,you should use '-fno-asm' following your gcc command.

lowpro2k3 · 08-02-2005, 10:41 PM

Cool, so did it work?

Code:

gcc -fno-asm -o progam program.c

I'm curious for my own purposes. I'll check out the gcc inline assembly docs when I get time, but I'm just wondering whether that command would work.

- lowpro2k3

bigapple · 08-03-2005, 12:03 AM

No, you needn't add the argument '-fno-asm' when you compile the program, just simply use "gcc -o program program.c" to compile you program which contians the inline assembly. you gcc compile can recognize the key word "asm",and understand the following Assembler Language.
And if you has define a varible such as "int asm = 4", then you should use the argument "-fno-asm" to force the gcc compiler ignore the key word "asm",just recognize the "asm" as a normal varible. Do you catch my mean?
for more information you can use 'man gcc'