14 Native Debugging

Several files control gdb's configuration for native support:

gdb/config/arch/xyz.mh
Specifies Makefile fragments needed by a native configuration on machine xyz. In particular, this lists the required native-dependent object files, by defining NATDEPFILES=.... Also specifies the header file which describes native support on xyz, by defining NAT_FILE= nm-xyz.h. You can also define NAT_CFLAGS, NAT_ADD_FILES, NAT_CLIBS, NAT_CDEPS, NAT_GENERATED_FILES, etc.; see Makefile.in.

Maintainer's note: The .mh suffix is because this file originally contained Makefile fragments for hosting gdb on machine xyz. While the file is no longer used for this purpose, the .mh suffix remains. Perhaps someone will eventually rename these fragments so that they have a .mn suffix.

gdb/config/arch/nm-xyz.h
(nm.h is a link to this file, created by configure). Contains C macro definitions describing the native system environment, such as child process control and core file support.
gdb/xyz-nat.c
Contains any miscellaneous C code required for this native support of this machine. On some machines it doesn't exist at all.

There are some “generic” versions of routines that can be used by various systems. These can be customized in various ways by macros defined in your nm-xyz.h file. If these routines work for the xyz host, you can just include the generic file's name (with .o, not .c) in NATDEPFILES.

Otherwise, if your machine needs custom support routines, you will need to write routines that perform the same functions as the generic file. Put them into xyz-nat.c, and put xyz-nat.o into NATDEPFILES.

inftarg.c
This contains the target_ops vector that supports Unix child processes on systems which use ptrace and wait to control the child.
procfs.c
This contains the target_ops vector that supports Unix child processes on systems which use /proc to control the child.
fork-child.c
This does the low-level grunge that uses Unix system calls to do a “fork and exec” to start up a child process.
infptrace.c
This is the low level interface to inferior processes for systems using the Unix ptrace call in a vanilla way.

14.1 ptrace

14.2 /proc

14.3 win32

14.4 shared libraries

14.5 Native Conditionals

When gdb is configured and compiled, various macros are defined or left undefined, to control compilation when the host and target systems are the same. These macros should be defined (or left undefined) in nm-system.h.

I386_USE_GENERIC_WATCHPOINTS
An x86-based machine can define this to use the generic x86 watchpoint support; see I386_USE_GENERIC_WATCHPOINTS.
SOLIB_ADD (filename, from_tty, targ, readsyms)
Define this to expand into an expression that will cause the symbols in filename to be added to gdb's symbol table. If readsyms is zero symbols are not read but any necessary low level processing for filename is still done.
SOLIB_CREATE_INFERIOR_HOOK
Define this to expand into any shared-library-relocation code that you want to be run just after the child process has been forked.
START_INFERIOR_TRAPS_EXPECTED
When starting an inferior, gdb normally expects to trap twice; once when the shell execs, and once when the program itself execs. If the actual number of traps is something other than 2, then define this macro to expand into the number expected.