Member Avatar for jay889000 
#include <stdio.h>
#include <stdlib.h>

#define PRECISION   3

double absD(double n)
{
asm(
"_absD: \n"
"pushl %ebp \n"
"fldz \n"
"movl %esp, %ebp \n"
"fldl 8(%ebp) \n"
"fxch %st(1) \n"
"fucomp %st(1) \n"
"fnstsw %ax \n"
"sahf \n"
"jbe L2 \n"
"fchs \n"
"L2: \n"
"popl %ebp \n"
"ret \n"
"fldl %[nIn]\n"
"fabs\n"
"fstpl %[nOut]\n"
: [nOut] "=m" (n)
: [nIn] "m" (n)
);
// do not change anything above this comment

    return n;

// do not change anything below this comment, except for printing out your name
}

int main(int argc, char **argv)
{
    double  n = 0.0;

    printf("CS201 - Assignment 02 - your name\n");
    if (argc > 1)
        n = atof(argv[1]);

    printf("abs(%.*f) = %.*f\n", PRECISION, n, PRECISION, absD(n));

    return 0;
}

I got an error saying parse error before string constant when I tried to compile it. I'm really new to C world . Any help would be appeciated !!

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  • Latest Post Latest Post by jay889000

Dani AI

Generated

As suggested, inline assembly is compiler-specific. On Cygwin you’re almost certainly using GCC, and GCC’s extended asm templates treat % specially. Single % before a register (for example %ebp) will be parsed as an asm-placeholder and can trigger “parse error before string constant.” Also note your code uses 32‑bit instructions/registers; if your compiler is targeting x86_64 that will cause additional errors.

Practical fixes:

  • Escape assembler register names by doubling the percent sign inside the template — e.g. use pushl %%ebp, movl %%esp, %%ebp, fnstsw %%ax, fxch %%st(1). Leave the GCC operand references like %[nIn] and %[nOut] as they are.
  • If you really intend to define a separate assembly function (you have a label and a ret), put that asm block at file scope or in a separate .s file. Embedding a full function prologue/epilogue inside inline asm placed inside another C function is dangerous and will confuse the compiler/assembler.
  • If your toolchain is 64‑bit, either compile for 32‑bit with -m32 or rewrite the assembly for x86_64 (different registers/ABI).

Troubleshooting tips: compile with gcc -Wall -Wextra -g and paste the exact gcc command plus the first few error lines if it still fails. A quick sanity check is to try asm("nop"); to confirm asm is accepted. If you post the compiler command and error output, people here can point to the exact line that needs fixing.

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Member Avatar for deceptikon

Inline assembly is very compiler dependent. Are you using the same compiler to build this program as your teacher used to write it?

Member Avatar for jay889000

I'm using cygwin to compile it !

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