Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
with the migration of old architectures to this new framework.
+Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
+unwinder framework, this consisting of a fresh new design featuring
+frame IDs, independent frame sniffers, and the sentinel frame. Mark
+Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
+libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
+trad unwinders. The architecture specific changes, each involving a
+complete rewrite of the architecture's frame code, were carried out by
+Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
+Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
+Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
+Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
+Weigand.
+
@node Sample Session
@chapter A Sample @value{GDBN} Session
and called functions.
@cindex frame, unwind
-@value{GDBN}'s current frame model is the result of an incremental
-cleanup of working code, not a fresh design, so it's a little weird.
-
-The natural model would have a frame object, with methods that read
-and write that frame's registers. Reading or writing the youngest
-frame's registers would simply read or write the processor's current
-registers, since the youngest frame is running directly on the
-processor. Older frames might have some registers saved on the stack
-by younger frames, so accessing the older frames' registers would do a
-mix of memory accesses and register accesses, as appropriate.
+@value{GDBN}'s frame model, a fresh design, was implemented with the
+need to support @sc{dwarf}'s Call Frame Information in mind. In fact,
+the term ``unwind'' is taken directly from that specification.
+Developers wishing to learn more about unwinders, are encouraged to
+read the the @sc{dwarf} specification.
@findex frame_register_unwind
-Instead, @value{GDBN}'s model is that you find a frame's registers by
-``unwinding'' them from the next younger frame. That is, to access
-the registers of frame #1 (the next-to-youngest frame), you actually
-apply @code{frame_register_unwind} to frame #0 (the youngest frame).
-But then the obvious question is: how do you access the registers of
-the youngest frame itself? How do you ``unwind'' them when they're
-not wound up?
+@findex get_frame_register
+@value{GDBN}'s model is that you find a frame's registers by
+``unwinding'' them from the next younger frame. That is,
+@samp{get_frame_register} which returns the value of a register in
+frame #1 (the next-to-youngest frame), is implemented by calling frame
+#0's @code{frame_register_unwind} (the youngest frame). But then the
+obvious question is: how do you access the registers of the youngest
+frame itself?
@cindex sentinel frame
@findex get_frame_type
is a sentinel frame, then @code{get_frame_type (@var{f}) ==
SENTINEL_FRAME}.
-@findex create_new_frame
-@vindex FRAME_FP
-@code{FRAME_FP} in the machine description has no meaning to the
-machine-independent part of @value{GDBN}, except that it is used when
-setting up a new frame from scratch, as follows:
-
-@smallexample
-create_new_frame (read_register (DEPRECATED_FP_REGNUM), read_pc ()));
-@end smallexample
-
-@cindex frame pointer register
-Other than that, all the meaning imparted to @code{DEPRECATED_FP_REGNUM}
-is imparted by the machine-dependent code. So,
-@code{DEPRECATED_FP_REGNUM} can have any value that is convenient for
-the code that creates new frames. (@code{create_new_frame} calls
-@code{DEPRECATED_INIT_EXTRA_FRAME_INFO} if it is defined; that is where
-you should use the @code{DEPRECATED_FP_REGNUM} value, if your frames are
-nonstandard.)
-
-@cindex frame chain
-Given a @value{GDBN} frame, define @code{DEPRECATED_FRAME_CHAIN} to
-determine the address of the calling function's frame. This will be
-used to create a new @value{GDBN} frame struct, and then
-@code{DEPRECATED_INIT_EXTRA_FRAME_INFO} and
-@code{DEPRECATED_INIT_FRAME_PC} will be called for the new frame.
-
@section Prologue Analysis
@cindex prologue analysis