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- Targets
- Using the new command
target, you can select at runtime whether
you are debugging local files, local processes, standalone systems over
a serial port, or realtime systems over a TCP/IP connection. The
command load can download programs into a remote system. Serial
stubs are available for Motorola 680x0, Intel 80386, and Sparc remote
systems; GDB also supports debugging realtime processes running under
VxWorks, using SunRPC Remote Procedure Calls over TCP/IP to talk to a
debugger stub on the target system. Internally, GDB now uses a function
vector to mediate access to different targets; if you need to add your
own support for a remote protocol, this makes it much easier.
- Watchpoints
- GDB now sports watchpoints as well as breakpoints. You can use a
watchpoint to stop execution whenever the value of an expression
changes, without having to predict a particular place in your program
where this may happen.
- Wide Output
- Commands that issue wide output now insert newlines at places designed
to make the output more readable.
- Object Code Formats
- GDB uses a new library called the Binary File Descriptor (BFD) Library
to permit it to switch dynamically, without reconfiguration or
recompilation, between different object-file formats. Formats currently
supported are COFF, ELF, a.out, Intel 960 b.out, MIPS ECOFF, HPPA SOM
(with stabs debugging), and S-records; files may be read as .o files,
archive libraries, or core dumps. BFD is available as a subroutine
library so that other programs may take advantage of it, and the other
GNU binary utilities are being converted to use it.
- Configuration and Ports
- Compile-time configuration (to select a particular architecture and
operating system) is much easier. The script
configure now
allows you to configure GDB as either a native debugger or a
cross-debugger. See section Installing GDB, for details on how to
configure.
- Interaction
- The user interface to the GDB control variables is simpler,
and is consolidated in two commands,
set and show. Output
lines are now broken at readable places, rather than overflowing onto
the next line. You can suppress output of machine-level addresses,
displaying only source language information.
- C++
- GDB now supports C++ multiple inheritance (if used with a GCC
version 2 compiler), and also has limited support for C++ exception
handling, with the commands
catch and info catch: GDB
can break when an exception is raised, before the stack is peeled back
to the exception handler's context.
- Modula-2
- GDB now has preliminary support for the GNU Modula-2 compiler, currently
under development at the State University of New York at Buffalo.
Coordinated development of both GDB and the GNU Modula-2 compiler will
continue. Other Modula-2 compilers are currently not supported, and
attempting to debug programs compiled with them will likely result in an
error as the symbol table of the executable is read in.
- Command Rationalization
- Many GDB commands have been renamed to make them easier to remember
and use. In particular, the subcommands of
info and
show/set are grouped to make the former refer to the state
of your program, and the latter refer to the state of GDB itself.
See section Renamed Commands, for details on what commands were renamed.
- Shared Libraries
- GDB 4 can debug programs and core files that use SunOS, SVR4, or IBM RS/6000
shared libraries.
- Threads
- On some systems, GDB 4 has facilities to debug multi-thread programs.
- Reference Card
- GDB 4 has a reference card. See section Formatting Documentation, for instructions about how to print it.
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