Info Catalog gdb: Stack gdb: Backtrace

gdb: Frames

 
 8.1 Stack Frames
 ================
 
 The call stack is divided up into contiguous pieces called "stack
 frames", or "frames" for short; each frame is the data associated with
 one call to one function.  The frame contains the arguments given to the
 function, the function's local variables, and the address at which the
 function is executing.
 
    When your program is started, the stack has only one frame, that of
 the function 'main'.  This is called the "initial" frame or the
 "outermost" frame.  Each time a function is called, a new frame is made.
 Each time a function returns, the frame for that function invocation is
 eliminated.  If a function is recursive, there can be many frames for
 the same function.  The frame for the function in which execution is
 actually occurring is called the "innermost" frame.  This is the most
 recently created of all the stack frames that still exist.
 
    Inside your program, stack frames are identified by their addresses.
 A stack frame consists of many bytes, each of which has its own address;
 each kind of computer has a convention for choosing one byte whose
 address serves as the address of the frame.  Usually this address is
 kept in a register called the "frame pointer register" ($fp
 Registers.) while execution is going on in that frame.
 
    GDB labels each existing stack frame with a "level", a number that is
 zero for the innermost frame, one for the frame that called it, and so
 on upward.  These level numbers give you a way of designating stack
 frames in GDB commands.  The terms "frame number" and "frame level" can
 be used interchangeably to describe this number.
 
    Some compilers provide a way to compile functions so that they
 operate without stack frames.  (For example, the GCC option
      '-fomit-frame-pointer'
    generates functions without a frame.)  This is occasionally done with
 heavily used library functions to save the frame setup time.  GDB has
 limited facilities for dealing with these function invocations.  If the
 innermost function invocation has no stack frame, GDB nevertheless
 regards it as though it had a separate frame, which is numbered zero as
 usual, allowing correct tracing of the function call chain.  However,
 GDB has no provision for frameless functions elsewhere in the stack.
 

Info Catalog gdb: Stack gdb: Backtrace