The problem with the assembly language is that there is no standard syntax, the most popular 2 syntax used to write assembly are the AT&T and Intel one.
Guess which one is being used by gcc, by default, and which one by Intel .
I suggest to use Intel syntax under gcc too so you can use just 1 syntax.
An example on how to generate asm with Intel syntax starting from sourcecode in C
gcc -S -masm=intel source.c