First, I have also posted this on ubuntuforums.org. I know that's bad form, but I don't think there will be many cross-readers here. The default address size is 64 bits in 64-bit mode. But when I look at the assembly language for the write() syscall, gcc uses only 32 bits of the address: .file "oneChar.c" .data .type aLetter, @object .size aLetter, 1 aLetter: .byte 65 .text .globl main .type main, @function main: pushq %rbp // <== 64-bit addresses movq %rsp, %rbp // <== movl $1, %edx movl $aLetter, %esi // <== 32-bit address movl $1, %edi call write movl $0, %eax leave ret .size main, .-main .ident "GCC: (GNU) 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)" .section .note.GNU-stack,"",@progbits Can anyone point me to discussions of what is going on here? Bob
