[Bug breakpoints/15902] New: Hardware watchpoints on remote targets do not automatically fall back to software watchpoints

[Bug breakpoints/15902] New: Hardware watchpoints on remote targets do not automatically fall back to software watchpoints

[jeremy.bennett at embecosm dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=15902

            Bug ID: 15902
           Summary: Hardware watchpoints on remote targets do not
                    automatically fall back to software watchpoints
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: breakpoints
          Assignee: unassigned at sourceware dot org
          Reporter: jeremy.bennett at embecosm dot com

Created attachment 7168
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7168&action=edit
Patch to update user manual for this issue.

The GDB manual (section 5.1.2, "Setting Watchpoints") states: "If gdb cannot
set a hardware watchpoint, it sets a software watchpoint,..."

This appears to only be true for native targets. On a remote target connecting
over Remote Serial Protocol, GDB will just report that hardware breakpoints are
not supported.

  Could not insert hardware breakpoints:
  You may have requested too many hardware breakpoints/watchpoints

The user must explicitly request software watchpoints using

  set can-use-hw-watchpoints 0

Problem found using GDB for ARC.

This really needs fixing in remote.c, but in the meantime, I attach a small
patch to the documentation:

2013-05-13  Jeremy Bennett  <jeremy.bennett@embecosm.com>

    * doc/gdb.texinfo (Setting Watchpoints): Note that automatic
    fallback to software watchpoints does not happen with remote
    targets.

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[Bug breakpoints/15902] Hardware watchpoints on remote targets do not automatically fall back to software watchpoints

[akolesov at synopsys dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=15902

Anton Kolesov <akolesov at synopsys dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |akolesov at synopsys dot com

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[Bug breakpoints/15902] Hardware watchpoints on remote targets do not automatically fall back to software watchpoints

[akolesov at synopsys dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=15902

--- Comment #1 from Anton Kolesov <akolesov at synopsys dot com> ---
I was able to reproduce this with x86_64 host and GDB 7.6 from release tarball
after I commented handling of Z2 packet in gdbserver source code.

  (gdb) watch a
  Hardware watchpoint 2: a
  (gdb) c
  Continuing.
  Warning:
  Could not insert hardware watchpoint 2.
  Could not insert hardware breakpoints:
  You may have requested too many hardware breakpoints/watchpoints.

  main () at test.c:4
  4           a = 2;
  (gdb)

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