diff options
Diffstat (limited to 'gdb/doc/gdb.texinfo')
| -rw-r--r-- | gdb/doc/gdb.texinfo | 70 |
1 files changed, 56 insertions, 14 deletions
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 92e4a21b392..d150881f608 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -2667,14 +2667,11 @@ is written into by the program and its value changes. @kindex rwatch @item rwatch @var{expr} Set a watchpoint that will break when watch @var{expr} is read by the program. -If you use both watchpoints, both must be set with the @code{rwatch} -command. @kindex awatch @item awatch @var{expr} Set a watchpoint that will break when @var{args} is read and written into -by the program. If you use both watchpoints, both must be set with the -@code{awatch} command. +by the program. @kindex info watchpoints @item info watchpoints @@ -2698,14 +2695,49 @@ Hardware watchpoint @var{num}: @var{expr} @noindent if it was able to set a hardware watchpoint. -The SPARClite DSU will generate traps when a program accesses -some data or instruction address that is assigned to the debug registers. -For the data addresses, DSU facilitates the @code{watch} command. -However the hardware breakpoint registers can only take two data watchpoints, -and both watchpoints must be the same kind. For example, you can set two -watchpoints with @code{watch} commands, two with @code{rwatch} -commands, @strong{or} two with @code{awatch} commands, but you cannot set one -watchpoint with one command and the other with a different command. +Currently, the @code{awatch} and @code{rwatch} commands can only set +hardware watchpoints, because accesses to data that don't change the +value of the watched expression cannot be detected without examining +every instruction as it is being executed, and @value{GDBN} does not do +that currently. If @value{GDBN} finds that it is unable to set a +hardware breakpoint with the @code{awatch} or @code{rwatch} command, it +will print a message like this: + +@smallexample +Expression cannot be implemented with read/access watchpoint. +@end smallexample + +Sometimes, @value{GDBN} cannot set a hardware watchpoint because the +data type of the watched expression is wider than what a hardware +watchpoint on the target machine can handle. For example, some systems +can only watch regions that are up to 4 bytes wide; on such systems you +cannot set hardware watchpoints for an expression that yields a +double-precision floating-point number (which is typically 8 bytes +wide). As a work-around, it might be possible to break the large region +into a series of smaller ones and watch them with separate watchpoints. + +If you set too many hardware watchpoints, @value{GDBN} might be unable +to insert all of them when you resume the execution of your program. +Since the precise number of active watchpoints is unknown until such +time as the program is about to be resumed, @value{GDBN} might not be +able to warn you about this when you set the watchpoints, and the +warning will be printed only when the program is resumed: + +@smallexample +Hardware watchpoint @var{num}: Could not insert watchpoint +@end smallexample + +@noindent +If this happens, delete or disable some of the watchpoints. + +The SPARClite DSU will generate traps when a program accesses some data +or instruction address that is assigned to the debug registers. For the +data addresses, DSU facilitates the @code{watch} command. However the +hardware breakpoint registers can only take two data watchpoints, and +both watchpoints must be the same kind. For example, you can set two +watchpoints with @code{watch} commands, two with @code{rwatch} commands, +@strong{or} two with @code{awatch} commands, but you cannot set one +watchpoint with one command and the other with a different command. @value{GDBN} will reject the command if you try to mix watchpoints. Delete or disable unused watchpoint commands before setting new ones. @@ -2713,6 +2745,16 @@ If you call a function interactively using @code{print} or @code{call}, any watchpoints you have set will be inactive until GDB reaches another kind of breakpoint or the call completes. +@value{GDBN} automatically deletes watchpoints that watch local +(automatic) variables, or expressions that involve 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, @emph{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 +@code{main} function and when it breaks, set all the watchpoints. + @quotation @cindex watchpoints and threads @cindex threads and watchpoints @@ -9820,11 +9862,11 @@ things without first using the debugger to find the facts. @c The readline documentation is distributed with the readline code @c and consists of the two following files: @c rluser.texinfo -@c inc-hist.texi +@c inc-hist.texinfo @c Use -I with makeinfo to point to the appropriate directory, @c environment var TEXINPUTS with TeX. @include rluser.texinfo -@include inc-hist.texi +@include inc-hist.texinfo @ifclear PRECONFIGURED |