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Re: [PATCH] Failure to stop at duplicate breakpoints


On 20/09/2012 7:40 PM, Sergio Durigan Junior wrote:
> On Thursday, September 20 2012, Andrew Burgess wrote:
> 
>> When two breakpoints are created at the same location, one of them is
>> marked as a duplicate.  When gdb inserts the breakpoints we only
>> really insert one breakpoint at any unique location.
>>
>> By creating duplicate breakpoints and deleting or disabling them in
>> the right order it is possible to get into a state where gdb has a
>> single breakpoint with a single location, but that location is marked
>> duplicate and so is never inserted, with the result we don't stop at
>> the breakpoint.
>>
>> Patch and test included below.
> 
> Thanks for the patches, but your mail client messed with them, probably.
> They are malformed in several places.

Sorry for the badly formatted patch, I believe I've fixed the issue, and
the version below should be more readable.

OK to apply?

Thanks,
Andrew


gdb/ChangeLog

2012-09-20  Andrew Burgess  <aburgess@broadcom.com>

	* breakpoint.c (update_global_location_list): Ignore previous
	duplicate status of a breakpoint when starting a new scan for
	duplicate breakpoints.


diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index b841bcd..f771d06 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -12463,7 +12463,7 @@ update_global_location_list (int should_insert)
       struct bp_location **loc_first_p;
       b = loc->owner;
 
-      if (!should_be_inserted (loc)
+      if (!unduplicated_should_be_inserted (loc)
 	  || !breakpoint_address_is_meaningful (b)
 	  /* Don't detect duplicate for tracepoint locations because they are
 	   never duplicated.  See the comments in field `duplicate' of

gdb/testsuite/ChangeLog

2012-09-20  Andrew Burgess  <aburgess@broadcom.com>

	* gdb.base/duplicate-bp.c: New file.
	* gdb.base/duplicate-bp.exp: New file.

diff --git a/gdb/testsuite/gdb.base/duplicate-bp.c b/gdb/testsuite/gdb.base/duplicate-bp.c
new file mode 100644
index 0000000..50145b4
--- /dev/null
+++ b/gdb/testsuite/gdb.base/duplicate-bp.c
@@ -0,0 +1,23 @@
+void
+spacer ()
+{
+  /* Nothing.  */
+}
+
+void
+breakpt ()
+{
+  /* Nothing.  */
+}
+
+int
+main ()
+{
+  spacer ();
+
+  breakpt ();
+
+  spacer ();
+  
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/duplicate-bp.exp b/gdb/testsuite/gdb.base/duplicate-bp.exp
new file mode 100644
index 0000000..021aa30
--- /dev/null
+++ b/gdb/testsuite/gdb.base/duplicate-bp.exp
@@ -0,0 +1,137 @@
+# Copyright 2012 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if { [prepare_for_testing duplicate-bp.exp "duplicate-bp" {duplicate-bp.c} {debug nowarnings}] } {
+    return -1
+}
+set srcfile "duplicate-bp.c"
+
+# Setup for the test, create COUNT breakpoints at the function BREAKPT.
+proc test_setup { count } {
+    upvar srcfile srcfile
+
+    clean_restart duplicate-bp
+
+    if ![runto_main] then { 
+	fail "can't run to main" 
+	return 0
+    }
+
+    for {set i 1} {$i <= $count} {incr i} {
+	gdb_breakpoint "breakpt"
+	gdb_test_no_output "set \$bp_num_${i} = \$bpnum"
+    }
+
+    gdb_test "step" "spacer \\(\\) at .*$srcfile:\[0-9\]+.*"
+    
+    return 1
+}
+
+
+# Test 1: Create two breakpoints at BREAKPT.  Delete #1 and expect to stop
+# at #2.
+test_setup 2
+
+gdb_test_no_output {delete $bp_num_1}
+
+gdb_test continue "Continuing\\..*Breakpoint \[0-9\]+, breakpt \\(\\) at .*$srcfile:\[0-9\]+.*" \
+			"delete #1, stop at #2"
+
+# Test 2: Create two breakpoints at BREAKPT.  Delete #2 and expect to stop
+# at #1.
+test_setup 2 
+
+gdb_test_no_output {delete $bp_num_2}
+
+gdb_test continue "Continuing\\..*Breakpoint \[0-9\]+, breakpt \\(\\) at .*$srcfile:\[0-9\]+.*" \
+			"delete #2, stop at #1"
+
+# Test 3: Create three breakpoints at BREAKPT.  Disable #1, delete #2,
+# expect to stop at #3.
+test_setup 3
+
+gdb_test_no_output {disable $bp_num_1}
+
+gdb_test "step" ".*"
+
+gdb_test_no_output {delete $bp_num_2}
+
+gdb_test continue "Continuing\\..*Breakpoint \[0-9\]+, breakpt \\(\\) at .*$srcfile:\[0-9\]+.*" \
+			"disable #1, delete #2, stop at #3"
+
+# Test 4: Create three breakpoints at BREAKPT.  Disable #2, delete #1,
+# expect to stop at #3.
+test_setup 3
+
+gdb_test_no_output {disable $bp_num_2}
+
+gdb_test "step" ".*"
+
+gdb_test_no_output {delete $bp_num_1}
+
+gdb_test continue "Continuing\\..*Breakpoint \[0-9\]+, breakpt \\(\\) at .*$srcfile:\[0-9\]+.*" \
+			"disable #2, delete #1, stop at #3"
+
+# Test 5: Create three breakpoints at BREAKPT.  Disable #1, delete #3,
+# expect to stop at #1.
+test_setup 3
+
+gdb_test_no_output {disable $bp_num_1}
+
+gdb_test "step" ".*"
+
+gdb_test_no_output {delete $bp_num_3}
+
+gdb_test continue "Continuing\\..*Breakpoint \[0-9\]+, breakpt \\(\\) at .*$srcfile:\[0-9\]+.*" \
+			"disable #1, delete #3, stop at #1"
+
+# Test 6: Create three breakpoints at BREAKPT.  Disable #3, delete #1,
+# expect to stop at #2.
+test_setup 3
+
+gdb_test_no_output {disable $bp_num_3}
+
+gdb_test "step" ".*"
+
+gdb_test_no_output {delete $bp_num_1}
+
+gdb_test continue "Continuing\\..*Breakpoint \[0-9\]+, breakpt \\(\\) at .*$srcfile:\[0-9\]+.*" \
+			"disable #3, delete #1, stop at #2"
+
+# Test 7: Create three breakpoints at BREAKPT.  Disable #2, delete #3,
+# expect to stop at #1.
+test_setup 3
+
+gdb_test_no_output {disable $bp_num_2}
+
+gdb_test "step" ".*"
+
+gdb_test_no_output {delete $bp_num_3}
+
+gdb_test continue "Continuing\\..*Breakpoint \[0-9\]+, breakpt \\(\\) at .*$srcfile:\[0-9\]+.*" \
+			"disable #2, delete #3, stop at #1"
+
+# Test 6: Create three breakpoints at BREAKPT.  Disable #3, delete #2,
+# expect to stop at #1.
+test_setup 3
+
+gdb_test_no_output {disable $bp_num_3}
+
+gdb_test "step" ".*"
+
+gdb_test_no_output {delete $bp_num_2}
+
+gdb_test continue "Continuing\\..*Breakpoint \[0-9\]+, breakpt \\(\\) at .*$srcfile:\[0-9\]+.*" \
+			"disable #3, delete #2, stop at #1"



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