GLib-GIO-message? What is it?

edit

It says, what exactly it writes. emacs uses this backed of gconf as the front-end communication with X, but as I was reading (over the Web), it needs also the dconf .

So, try to install dconf and see if the message disappears.

yum install dconf dconf-editor

If you "Google" the warning message, you will find similar reports. Though I'm not sure if you need to report this as a bug (package maintain bug), where you will ask for dconf to be included as a dependency for emacs.

When I use gcc, should I use -m64 option??

If you read the manual page for gcc

These -m switches are supported in addition to the above on x86-64 processors in 64-bit environments.

-m32

-m64

-mx32

Generate code for a 32-bit or 64-bit environment. The -m32 option sets "int", "long", and pointer types to 32 bits, and generates code that runs on any i386 system.

The -m64 option sets "int" to 32 bits and "long" and pointer types to 64 bits, and generates code for the x86-64 architecture. For Darwin only the -m64 option also turns off the -fno-pic and -mdynamic-no-pic options.

so, do as you need.