On 10/15/07, Curt Wohlgemuth <[EMAIL PROTECTED]> wrote: > > > Related to this, and exposing my ignorance of the architecture, I'm > confused > by register values returned by gdb during the attach case above. The > value > of "$rbp" is 0x7ffff9f3bf40; the value of "$fp" is 0x7ffff9f3bf00. I > thought that RBP holds the frame pointer; what would "$fp" be then, and > why > would it be different? The value at address "$fp + 0x8" is actually the > return address I'm expecting (0x402923).
$fp seems to be a variable gdb maintains to track the frame pointer. When you use -fomit-frame-pointer on x64, $rbp becomes a scratch register for the compiler (this is the default with gcc -O2 and higher). Otherwise, $fp and $rbp should be equal. -Arun
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