@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
@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.
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
@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
projects / deliverable / binutils-gdb.git / blobdiff