I am creating a GCC (4.5.2) that uses a modified libgomp. My libgomp has a file that contains the following line of code: asm volatile("mov %%rbp, %0" : "=m" (rbp) ); I attempted to compile this on a 64-bit machine running under 64-bit Ubuntu: $ uname -a Linux dedis 2.6.32-27-server #49-Ubuntu SMP Thu Dec 2 02:05:21 UTC 2010 x86_64 GNU/Linux But my build failed, with the assembler error that "rbp" was an unrecognized register name. I changed this to ebp, and it compiled fine. However, my code then failed, presumably because it was getting an invalid address. I figured out a workaround that seems fine, but I wanted to know why I was getting this assembler error and what I should have done about it. Thank you! Amittai Aviram PhD Student in Computer Science Yale University 646 483 2639 amittai.aviram@xxxxxxxx http://www.amittai.com