On Thu, Feb 13, 2003 at 12:07:57PM -0800, Long Li wrote:

Hi,

I am using a gcc 3.0.4 MIPS crosscompiler on Redhat. I
found something interesting: when I use specifly -O1
for compilation, and I can use memcpy function even I
did not tell the compiler where I declard it or define
it. However, when I specify -O0, then the compiler
tells me undefined reference to this memcpy function.
So my questions are:

1. Is memcpy a built-in function for gcc? But why not
for optimization level 0?

Because using it is an optimization.

2. Besides memcpy, is there any other functions built
in too?

Lots.  The list varies depending on the GCC version; see the manual.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer