From e94a679a11af21512dbb8b538ddc49e66bd33039 Mon Sep 17 00:00:00 2001 From: Jim Blandy Date: Wed, 12 Sep 2001 19:49:52 +0000 Subject: [PATCH] Remove incomplete section on overlays, committed by accident. --- gdb/doc/gdb.texinfo | 79 --------------------------------------------- 1 file changed, 79 deletions(-) diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 4c4ee9f1d4c..b40de03f000 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -127,7 +127,6 @@ Copyright (C) 1988-2001 Free Software Foundation, Inc. * Source:: Examining source files * Data:: Examining data * Tracepoints:: Debugging remote targets non-intrusively -* Overlays:: Debugging programs that use overlays * Languages:: Using @value{GDBN} with different languages @@ -180,7 +179,6 @@ Copyright (C) 1988-2000 Free Software Foundation, Inc. * Source:: Examining source files * Data:: Examining data * Tracepoints:: Debugging remote targets non-intrusively -* Overlays:: Debugging programs that use overlays * Languages:: Using @value{GDBN} with different languages @@ -6282,83 +6280,6 @@ data. > end @end smallexample -@node Overlays -@chapter Debugging Programs That Use Overlays -@cindex overlays -@kindex overlay -@kindex ovly @r{(@code{ovly})} - -If your program is too large to fit completely in your target system's -memory, you can sometimes use @dfn{overlays} to work around this -problem. @value{GDBN} provides some support for programs that use -overlays. - -@menu -* How Overlays Work:: A general explanation of overlays. -@end menu - -@node How Overlays Work -@section How Overlays Work - -Suppose you have a computer whose instruction address space is only 64 -kilobytes long, but which has much more memory that can be accessed by -other means: special instructions, segment registers, or bank switch -registers, for example. Suppose further that you want to adapt a -program which is larger than 64 kilobytes to run on this system. - -One solution is to identify modules of your program which are relatively -independent, and need not call each other directly; call these modules -@dfn{overlays}. Separate the overlays from the main program, and place -their machine code in the larger memory. Place your main program in -instruction memory, but leave at least enough space there to hold the -largest overlay as well. Now, to call a function located in an overlay, -you must first copy that overlay's machine code from the large memory -into the space set aside for it in the instruction memory, and then jump -to its code. - -An overlay loaded into instruction memory and ready for use is called a -@dfn{mapped} overlay; its @dfn{mapped address} is its address in the -instruction memory. An overlay not present (or only partial present) in -instruction memory is called @dfn{unmapped}; its @dfn{load address} is -its address in the larger memory. - -Overlays introduce a number of complications: -@itemize bullet - -@item -Since you cannot have all your overlays loaded at once, - - -This will probably overwrite the -previous overlay loaded in that space; you will need to re-load - - - - -modify your main program such that, before it calls a function located -in an overlay, it first copies that overlay from the large memory into -the instruction memory. - - - - -copy the overlay into -place - - -want to run which is larger than 64 kilobytes. - - - - a 64kb instruction address -space. - -to run on a system which has a small -amount of memory available from which it can execute machine -instructions, and a large amount of separate data memory, - - - @node Languages @chapter Using @value{GDBN} with Different Languages @cindex languages -- 2.30.2