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GDB 4.0 -- what has changed since 3.5?
* New Facilities
Wide output is wrapped at good places to make the output more
readable.
Gdb now supports cross-debugging from a host machine of one type to a
target machine of another type. Communication with the target system
is over serial lines. The ``target'' command handles connecting to the
remote system; the ``load'' command will download a program into the
remote system. It also supports debugging of realtime processes
running under VxWorks, using SunRPC Remote Procedure Calls over TCP/IP
to talk to a debugger stub on the target system.
New CPUs supported include the AMD 29000 and Intel 960.
GDB now reads object files and symbol tables via a ``binary file''
library, which allows a single copy of GDB to debug programs of multiple
object file types such as a.out and coff.
There is now a GDB reference card in "gdbrc.tex".
* Control-Variable user interface simplified
All variables that control the operation of the debugger can be set
by the ``set'' command, and displayed by the ``show'' command.
For example, ``set prompt new-gdb=>'' will change your prompt to new-gdb=>.
``Show prompt'' produces the response:
Gdb's prompt is new-gdb=>.
What follows are the NEW set commands. The command ``help set'' will
print a complete list of old and new set commands. ``help set FOO''
will give a longer description of the variable FOO.
confirm on/off: Enables warning questions for operations that are
hard to recover from, e.g. rerunning the program while
it is already running. Default is ON.
editing on/off: Enables EMACS style command line editing
of input. Previous lines can be recalled with
control-P, the current line can be edited with control-B,
you can search for commands with control-R, etc.
Default is ON.
history filename NAME: NAME is where the gdb command history
will be stored. The default is .gdb_history,
or the value of the environment variable
GDBHISTFILE.
history size N: The size, in commands, of the command history. The
default is 256, or the value of the environment variable
HISTSIZE.
history write on/off: If this value is set to ON, the history file will
be saved after exiting gdb. If set to OFF, the
file will not be saved. The default is OFF.
history expansion on/off: If this value is set to ON, then csh-like
history expansion will be performed on
command line input. The default is OFF.
radix N: Sets the default radix for input and output. It can be set
to 8, 10, or 16. Note that the argument to "radix" is interpreted
in the current radix, so "set radix 10" is always a no-op.
screen-height N: This integer value is the number of lines on a page. Default
is 24, the current `stty rows'' setting, or the ``li#''
setting from the termcap entry matching the environment
variable TERM.
screen-width N: This integer value is the number of characters on a line.
Default is 80, the current `stty cols'' setting, or the ``co#''
setting from the termcap entry matching the environment
variable TERM.
Note: ``set screensize'' is obsolete. Use ``set height'' and
``set width'' instead.
print address on/off: Print memory addresses in various command displays,
such as stack traces and structure values. Gdb looks
more ``symbolic'' if you turn this off; it looks more
``machine level'' with it on. Default is ON.
print array on/off: Prettyprint arrays. New convenient format! Default
is OFF.
print demangle on/off: Print C++ symbols in "source" form if on,
"raw" form if off.
print asm-demangle on/off: Same, for assembler level printouts
like instructions.
print vtbl on/off: Prettyprint C++ virtual function tables. Default is OFF.
* Support for Epoch Environment.
The epoch environment is a version of Emacs v18 with windowing. One
new command, ``inspect'', is identical to ``print'', except that if you
are running in the epoch environment, the value is printed in its own
window.
* Support for Shared Libraries
GDB can now debug programs and core files that use SunOS shared libraries.
Symbols from a shared library cannot be referenced
before the shared library has been linked with the program (this
happens after you type ``run'' and before the function main() is entered).
At any time after this linking (including when examining core files
from dynamically linked programs), gdb reads the symbols from each
shared library when you type the ``sharedlibrary'' command.
It can be abbreviated ``share''.
sharedlibrary REGEXP: Load shared object library symbols for files
matching a unix regular expression. No argument
indicates to load symbols for all shared libraries.
info sharedlibrary: Status of loaded shared libraries.
* Watchpoints
A watchpoint stops execution of a program whenever the value of an
expression changes. Checking for this slows down execution
tremendously whenever you are in the scope of the expression, but is
quite useful for catching tough ``bit-spreader'' or pointer misuse
problems. Some machines such as the 386 have hardware for doing this
more quickly, and future versions of gdb will use this hardware.
watch EXP: Set a watchpoint (breakpoint) for an expression.
info watchpoints: Information about your watchpoints.
delete N: Deletes watchpoint number N (same as breakpoints).
disable N: Temporarily turns off watchpoint number N (same as breakpoints).
enable N: Re-enables watchpoint number N (same as breakpoints).
* C++ multiple inheritance
When used with a GCC version 2 compiler, GDB supports multiple inheritance
for C++ programs.
* C++ exception handling
Gdb now supports limited C++ exception handling. Besides the existing
ability to breakpoint on an exception handler, gdb can breakpoint on
the raising of an exception (before the stack is peeled back to the
handler's context).
catch FOO: If there is a FOO exception handler in the dynamic scope,
set a breakpoint to catch exceptions which may be raised there.
Multiple exceptions (``catch foo bar baz'') may be caught.
info catch: Lists all exceptions which may be caught in the
current stack frame.
* Minor command changes
The command ``call func (arg, arg, ...)'' now acts like the print
command, except it does not print or save a value if the function's result
is void. This is similar to dbx usage.
The ``up'' and ``down'' commands now always print the frame they end up
at; ``up-silently'' and `down-silently'' can be used in scripts to change
frames without printing.
* New directory command
'dir' now adds directories to the FRONT of the source search path.
The path starts off empty. Source files that contain debug information
about the directory in which they were compiled can be found even
with an empty path; GCC includes this information. If GDB can't find
your source file in the current directory, type "dir .".
* Features removed in this release
``info types'' has been removed, since it printed builtin types in a
confusing fashion, and did not do useful things with typedefs. ``ptype''
or ``whatis'' are more useful commands for dealing with types..
* Configuring GDB for compilation
For normal use, type ``config.gdb host''. Hosts now handled are:
3b1 altos altosgas arm bigmips convex hp300bsd hp300hpux i386v i386v-g
i386v32 i386v32-g isi littlemips m88k merlin news news1000 none np1 pn
pyramid sun2os3 sun2os4 sun386 sun3os3 sun3os4 sun4os3 sun4os4 symmetry
umax vax
Type config.gdb +host to get a full description of each host.
You can now build gdb conveniently for several architectures from the
same sources. If config.gdb is run from a subdirectory, it configures
the Makefile to use source files from '..'. Each subdirectory can be
indpendently configured. An explicit source file directory can also
be specified with the +srcdir=xxx option. Due to obscure search rules
in the C preprocessor, if you have previously built gdb in the main
directory, run 'make cleanconfig' in the top level directory before
building it in a subdirectory.
GDB now handles cross debugging. If you are remotely debugging between
two different machines, type ``config.gdb host target''.
Host is the machine where gdb will run; target is the machine
where the program that you are debugging will run.
Type config.gdb +target to get a full description of each target.
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