GNAT Installation Problems

[csampson@inetworld.net (Charles H. Sampson)]

After years of playing with Ada on my antique Mac G4 (desktop), I
decided to move to my much more modern MacBook Pro, running OS-X 10.7. I
downloaded what I think is the proper file from libre.adacore.com:
x86_64-Darwin. I also downloaded and installed Xquartz.

In a terminal window, I executed doinstall and followed instructions,
placing the GNAT files in folder Ada/GNAT. I changed my .bashrc to put
/Ada/GNAT at the head of PATH. I then followed the instructions for
"codesigning" gdb, I hope. I created a certificate that I named GDB.
After rebooting the machine, as instructed, I executed

     codesign -f -a GDB /Ada/GNAT/bin/gdb

and was rewarded with the error message

     GDB: unknown architecture name

Finally, trying to get a handle on where I stand, I executed (in a
terminal window)

     gnatmake -g generate.adb

which gave me the message

     Illegal instruction: 4

Any ideas? The last message makes me think that my MacBook has only a
32-bit bus and it's trying to execute an instruction unique to 64-bit
machines. I've poked around System Profiler and see nothing about bus
width.

Charlie
-- 
Nobody in this country got rich on his own.  You built a factory--good.
But you moved your goods on roads we all paid for.  You hired workers we
all paid to educate. So keep a big hunk of the money from your factory.
But take a hunk and pay it forward.  Elizabeth Warren (paraphrased)