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* gdbint.texinfo (Algorithms): More accurate description of

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STOPPED_BY_WATCHPOINT.  Point out that target_stopped_data_address
	is not needed unless data-read and data-access watchpoints are
	supported.  Add a description of how GDB checks whether the
	inferior stopped because a watchpoint was hit.
This commit is contained in:
Eli Zaretskii 2004-12-04 14:02:44 +00:00
parent 256d90da48
commit b6b8ece66c
2 changed files with 42 additions and 7 deletions
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8
gdb/doc/ChangeLog
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@ -1,3 +1,11 @@
2004-12-04 Eli Zaretskii <eliz@gnu.org>
* gdbint.texinfo (Algorithms): More accurate description of
STOPPED_BY_WATCHPOINT. Point out that target_stopped_data_address
is not needed unless data-read and data-access watchpoints are
supported. Add a description of how GDB checks whether the
inferior stopped because a watchpoint was hit.
2004-11-23 Eli Zaretskii <eliz@gnu.org>
* gdb.texinfo (Files): Add cross-reference to description of

41
gdb/doc/gdbint.texinfo
View file

@ -397,6 +397,18 @@ single-step the program being debugged and test the value of the
watched expression(s) after each instruction. The rest of this
section is mostly irrelevant for software watchpoints.
When the inferior stops, @value{GDBN} tries to establish, among other
possible reasons, whether it stopped due to a watchpoint being hit.
For a data-write watchpoint, it does so by evaluating, for each
watchpoint, the expression whose value is being watched, and testing
whether the watched value has changed. For data-read and data-access
watchpoints, @value{GDBN} needs the target to supply a primitive that
returns the address of the data that was accessed or read (see the
description of @code{target_stopped_data_address} below): if this
primitive returns a valid address, @value{GDBN} infers that a
watchpoint triggered if it watches an expression whose evaluation uses
that address.
@value{GDBN} uses several macros and primitives to support hardware
watchpoints:
@ -431,17 +443,18 @@ defined.
@findex TARGET_DISABLE_HW_WATCHPOINTS
@item TARGET_DISABLE_HW_WATCHPOINTS (@var{pid})
Disables watchpoints in the process identified by @var{pid}. This is
used, e.g., on HP-UX which provides operations to disable and enable
the page-level memory protection that implements hardware watchpoints
on that platform.
used, e.g., on HPPA-RISC machines running HP-UX, which provide
operations to disable and enable the page-level memory protection that
implements hardware watchpoints on that platform.
@findex TARGET_ENABLE_HW_WATCHPOINTS
@item TARGET_ENABLE_HW_WATCHPOINTS (@var{pid})
Enables watchpoints in the process identified by @var{pid}. This is
used, e.g., on HP-UX which provides operations to disable and enable
the page-level memory protection that implements hardware watchpoints
on that platform.
used, e.g., on HPPA-RISC machines running HP-UX, which provide
operations to disable and enable the page-level memory protection that
implements hardware watchpoints on that platform.
@cindex insert or remove hardware watchpoint
@findex target_insert_watchpoint
@findex target_remove_watchpoint
@item target_insert_watchpoint (@var{addr}, @var{len}, @var{type})
@ -480,7 +493,11 @@ two macros can use them for their internal purposes.
@item target_stopped_data_address (@var{addr_p})
If the inferior has some watchpoint that triggered, place the address
associated with the watchpoint at the location pointed to by
@var{addr_p} and return non-zero. Otherwise, return zero.
@var{addr_p} and return non-zero. Otherwise, return zero. Note that
this primitive is used by @value{GDBN} only on targets that support
data-read or data-access type watchpoints, so targets that have
support only for data-write watchpoints need not implement these
primitives.
@findex HAVE_STEPPABLE_WATCHPOINT
@item HAVE_STEPPABLE_WATCHPOINT
@ -506,6 +523,16 @@ watchpoints before stepping the inferior.
@item STOPPED_BY_WATCHPOINT (@var{wait_status})
Return non-zero if stopped by a watchpoint. @var{wait_status} is of
the type @code{struct target_waitstatus}, defined by @file{target.h}.
Normally, this macro is defined to invoke the function pointed to by
the @code{to_stopped_by_watchpoint} member of the structure (of the
type @code{target_ops}, defined on @file{target.h}) that describes the
target-specific operations; @code{to_stopped_by_watchpoint} ignores
the @var{wait_status} argument.
@value{GDBN} does not require the non-zero value returned by
@code{STOPPED_BY_WATCHPOINT} to be 100% correct, so if a target cannot
determine for sure whether the inferior stopped due to a watchpoint,
it could return non-zero ``just in case''.
@end table
@subsection x86 Watchpoints