40
Chapter 7. Stopping and Continuing
gdb automatically deletes watchpoints that watch local (automatic) variables, or expressions that in-
volve such variables, when they go out of scope, that is, when the execution leaves the block in which
these variables were defined. In particular, when the program being debugged terminates,
all
local
variables go out of scope, and so only watchpoints that watch global variables remain set. If you rerun
the program, you will need to set all such watchpoints again. One way of doing that would be to set a
code breakpoint at the entry to the
main
function and when it breaks, set all the watchpoints.
Warning:
In multi-thread programs, watchpoints have only limited usefulness. With the current watchpoint
implementation, gdb can only watch the value of an expression
in a single thread
. If you are confident that
the expression can only change due to the current thread’s activity (and if you are also confident that no
other thread can become current), then you can use watchpoints as usual. However, gdb may not notice
when a non-current thread’s activity changes the expression.
HP-UX Warning:
In multi-thread programs, software watchpoints have only limited usefulness. If gdb cre-
ates a software watchpoint, it can only watch the value of an expression
in a single thread
. If you are
confident that the expression can only change due to the current thread’s activity (and if you are also con-
fident that no other thread can become current), then you can use software watchpoints as usual. However,
gdb may not notice when a non-current thread’s activity changes the expression. (Hardware watchpoints, in
contrast, watch an expression in all threads.)
7.1.3. Setting catchpoints
You can use
catchpoints
to cause the debugger to stop for certain kinds of program events, such as
C
++
exceptions or the loading of a shared library. Use the
catch
command to set a catchpoint.
catch
event
Stop when
event
occurs.
event
can be any of the following:
throw
The throwing of a C
++
exception.
catch
The catching of a C
++
exception.
exec
A call to
exec
. This is currently only available for HP-UX.
fork
A call to
fork
. This is currently only available for HP-UX.
vfork
A call to
vfork
. This is currently only available for HP-UX.
load
load
libname
The dynamic loading of any shared library, or the loading of the library
libname
. This is
currently only available for HP-UX.
Summary of Contents for ENTERPRISE LINUX 4 - DEVELOPER TOOLS GUIDE
Page 1: ...Red Hat Enterprise Linux 4 Debugging with gdb ...
Page 12: ...2 Chapter 1 Debugging with gdb ...
Page 28: ...18 Chapter 4 Getting In and Out of gdb ...
Page 34: ...24 Chapter 5 gdb Commands ...
Page 44: ...34 Chapter 6 Running Programs Under gdb ...
Page 68: ...58 Chapter 8 Examining the Stack ...
Page 98: ...88 Chapter 10 Examining Data ...
Page 112: ...102 Chapter 12 Tracepoints ...
Page 118: ...108 Chapter 13 Debugging Programs That Use Overlays ...
Page 138: ...128 Chapter 14 Using gdb with Different Languages ...
Page 144: ...134 Chapter 15 Examining the Symbol Table ...
Page 170: ...160 Chapter 19 Debugging remote programs ...
Page 198: ...188 Chapter 21 Controlling gdb ...
Page 204: ...194 Chapter 22 Canned Sequences of Commands ...
Page 206: ...196 Chapter 23 Command Interpreters ...
Page 216: ...206 Chapter 25 Using gdb under gnu Emacs ...
Page 296: ...286 Chapter 27 gdb Annotations ...
Page 300: ...290 Chapter 28 Reporting Bugs in gdb ...
Page 322: ...312 Chapter 30 Using History Interactively ...
Page 362: ...352 Appendix D gdb Remote Serial Protocol ...
Page 380: ...370 Appendix F GNU GENERAL PUBLIC LICENSE ...
Page 386: ...376 Appendix G GNU Free Documentation License ...
Page 410: ......