[PATCH 03/12] gdb: include breakpoint number in testing condition error message

[Andrew Burgess <aburgess@redhat.com>]

When GDB fails to test the condition of a conditional breakpoint, for
whatever reason, the error message looks like this:

  (gdb) break foo if (*(int *) 0) == 1
  Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
  (gdb) r
  Starting program: /tmp/bpcond
  Error in testing breakpoint condition:
  Cannot access memory at address 0x0

  Breakpoint 1, foo () at bpcond.c:11
  11	  int a = 32;
  (gdb)

The line I'm interested in for this commit is this one:

  Error in testing breakpoint condition:

In the case above we can figure out that the problematic breakpoint
was #1 because in the final line of the message GDB reports the stop a
breakpoint #1.

However, in the next few patches I plan to change this.  In some cases
I don't think it makes sense for GDB to report the stop as being at
breakpoint #1, consider this case:

  (gdb) list some_func
  1	int
  2	some_func ()
  3	{
  4	  int *p = 0;
  5	  return *p;
  6	}
  7
  8	void
  9	foo ()
  10	{
  (gdb) break foo if (some_func ())
  Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
  (gdb) r
  Starting program: /tmp/bpcond

  Program received signal SIGSEGV, Segmentation fault.
  0x0000000000401116 in some_func () at bpcond.c:5
  5	  return *p;
  Error in testing breakpoint condition:
  The program being debugged was signaled while in a function called from GDB.
  GDB remains in the frame where the signal was received.
  To change this behavior use "set unwindonsignal on".
  Evaluation of the expression containing the function
  (some_func) will be abandoned.
  When the function is done executing, GDB will silently stop.

  Program received signal SIGSEGV, Segmentation fault.

  Breakpoint 1, 0x0000000000401116 in some_func () at bpcond.c:5
  5	  return *p;
  (gdb)

Notice that, the final lines of output report the stop as being at
breakpoint #1, even though we are actually located within some_func.

I find this behaviour confusing, and propose that this should be
changed.  However, if I make that change then every reference to
breakpoint #1 will be lost from the error message.

So, in this commit, in preparation for the later commits, I propose to
change the 'Error in testing breakpoint condition:' line to this:

  Error in testing condition for breakpoint NUMBER:

where NUMBER will be filled in as appropriate.  Here's the first
example with the updated error:

  (gdb) break foo if (*(int *) 0) == 0
  Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
  (gdb) r
  Starting program: /tmp/bpcond
  Error in testing condition for breakpoint 1:
  Cannot access memory at address 0x0

  Breakpoint 1, foo () at bpcond.c:11
  11	  int a = 32;
  (gdb)

The breakpoint number does now appear twice in the output, but I don't
see that as a negative.

This commit just changes the one line of the error, and updates the
few tests that either included the old error in comments, or actually
checked for the error in the expected output.

As the only test that checked the line I modified is a Python test,
I've added a new test that doesn't rely on Python that checks the
error message in detail.

While working on the new test, I spotted that it would fail when run
with native-gdbserver and native-extended-gdbserver target boards.
This turns out to be due to a gdbserver bug.  To avoid cluttering this
commit I've added a work around to the new test script so that the
test passes for the remote boards, in the next few commits I will fix
gdbserver, and update the test script to remove the work around.
---
 gdb/breakpoint.c                              |  3 +-
 gdb/testsuite/gdb.base/bp-cond-failure.c      | 30 +++++++
 gdb/testsuite/gdb.base/bp-cond-failure.exp    | 83 +++++++++++++++++++
 .../gdb.base/catch-signal-siginfo-cond.exp    |  2 +-
 gdb/testsuite/gdb.base/gnu-ifunc.exp          |  2 +-
 .../gdb.python/py-finish-breakpoint.exp       |  2 +-
 gdb/testsuite/lib/gdb.exp                     |  8 ++
 7 files changed, 126 insertions(+), 4 deletions(-)
 create mode 100644 gdb/testsuite/gdb.base/bp-cond-failure.c
 create mode 100644 gdb/testsuite/gdb.base/bp-cond-failure.exp

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 91e13a03360..4f5a27a6fe8 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -5412,7 +5412,8 @@ bpstat_check_breakpoint_conditions (bpstat *bs, thread_info *thread)
 	  catch (const gdb_exception &ex)
 	    {
 	      exception_fprintf (gdb_stderr, ex,
-				 "Error in testing breakpoint condition:\n");
+				 "Error in testing condition for breakpoint %d:\n",
+				 b->number);
 	    }
 	}
       else
diff --git a/gdb/testsuite/gdb.base/bp-cond-failure.c b/gdb/testsuite/gdb.base/bp-cond-failure.c
new file mode 100644
index 00000000000..be9d1fdcf2d
--- /dev/null
+++ b/gdb/testsuite/gdb.base/bp-cond-failure.c
@@ -0,0 +1,30 @@
+/* Copyright 2022 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+int
+foo ()
+{
+  return 0;	/* Breakpoint here.  */
+}
+
+int
+main ()
+{
+  int res = foo ();
+
+  return res;
+}
diff --git a/gdb/testsuite/gdb.base/bp-cond-failure.exp b/gdb/testsuite/gdb.base/bp-cond-failure.exp
new file mode 100644
index 00000000000..6f89771d187
--- /dev/null
+++ b/gdb/testsuite/gdb.base/bp-cond-failure.exp
@@ -0,0 +1,83 @@
+# Copyright 2022 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/>.
+
+# Check the format of the error message given when a breakpoint
+# condition fails.
+#
+# In this case the breakpoint condition does not make use of inferior
+# function calls, instead, the expression used for the breakpoint
+# condition will throw an error when evaluated.
+#
+# We check that the correct breakpoint number appears in the error
+# message, and that the error is reported at the correct source
+# location.
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" ${binfile} "${srcfile}" \
+	  {debug}] == -1 } {
+    return
+}
+
+# This test relies on reading address zero triggering a SIGSEGV.
+if { [is_address_zero_readable] } {
+    return
+}
+
+# Where the breakpoint will be placed.
+set bp_line [gdb_get_line_number "Breakpoint here"]
+
+proc run_test { cond_eval } {
+    clean_restart ${::binfile}
+
+    if {![runto_main]} {
+	fail "run to main"
+	return -1
+    }
+
+    if { $cond_eval != "auto" } {
+	gdb_test_no_output "set breakpoint condition-evaluation ${cond_eval}"
+    }
+
+    # Setup the conditional breakpoint and record its number.
+    gdb_breakpoint "${::srcfile}:${::bp_line} if (*(int *) 0) == 0"
+    set bp_num [get_integer_valueof "\$bpnum" "*UNKNOWN*"]
+
+    gdb_test "continue" \
+	[multi_line \
+	     "Continuing\\." \
+	     "Error in testing condition for breakpoint ${bp_num}:" \
+	     "Cannot access memory at address 0x0" \
+	     "" \
+	     "Breakpoint ${bp_num}, foo \\(\\) at \[^\r\n\]+:${::bp_line}" \
+	     "${::decimal}\\s+\[^\r\n\]+Breakpoint here\[^\r\n\]+"]
+}
+
+# If we're using a remote target then conditions could be evaulated
+# locally on the host, or on the remote target.  Otherwise, conditions
+# are always evaluated locally (which is what auto will select).
+#
+# NOTE: 'target' is not included here for remote targets as a
+# gdbserver bug prevents the test from passing.  This will be fixed in
+# the next commit, and this test updated.
+if { [gdb_is_remote_or_extended_remote_target] } {
+    set cond_eval_modes { "host" }
+} else {
+    set cond_eval_modes { "auto" }
+}
+
+foreach_with_prefix cond_eval $cond_eval_modes {
+    run_test $cond_eval
+}
diff --git a/gdb/testsuite/gdb.base/catch-signal-siginfo-cond.exp b/gdb/testsuite/gdb.base/catch-signal-siginfo-cond.exp
index 85a55b29ea5..d5fdbae2409 100644
--- a/gdb/testsuite/gdb.base/catch-signal-siginfo-cond.exp
+++ b/gdb/testsuite/gdb.base/catch-signal-siginfo-cond.exp
@@ -18,7 +18,7 @@
 #
 # (gdb) continue
 # Continuing.
-# Error in testing breakpoint condition:
+# Error in testing condition for breakpoint NUM:
 # Selected thread is running.
 #
 # Catchpoint 3 (signal SIGUSR1), 0x0000003615e35877 in __GI_raise (sig=10) at raise.c:56
diff --git a/gdb/testsuite/gdb.base/gnu-ifunc.exp b/gdb/testsuite/gdb.base/gnu-ifunc.exp
index 3fbf237c71c..cbdcbbf07b4 100644
--- a/gdb/testsuite/gdb.base/gnu-ifunc.exp
+++ b/gdb/testsuite/gdb.base/gnu-ifunc.exp
@@ -282,7 +282,7 @@ proc misc_tests {resolver_attr resolver_debug final_debug} {
 
     # Also test a former patch regression:
     # Continuing.
-    # Error in testing breakpoint condition:
+    # Error in testing condition for breakpoint NUM:
     # Attempt to take address of value not located in memory.
     #
     # Breakpoint 2, main () at ./gdb.base/gnu-ifunc.c:33
diff --git a/gdb/testsuite/gdb.python/py-finish-breakpoint.exp b/gdb/testsuite/gdb.python/py-finish-breakpoint.exp
index c525337990e..d873fd5cd0f 100644
--- a/gdb/testsuite/gdb.python/py-finish-breakpoint.exp
+++ b/gdb/testsuite/gdb.python/py-finish-breakpoint.exp
@@ -193,7 +193,7 @@ with_test_prefix "finish in normal frame" {
     gdb_test "python TestBreakpoint()" "TestBreakpoint init" "set BP in condition"
 
     gdb_test "continue" \
-	"test don't stop: 1.*test don't stop: 2.*test stop.*Error in testing breakpoint condition.*The program being debugged stopped while in a function called from GDB.*" \
+	"test don't stop: 1.*test don't stop: 2.*test stop.*Error in testing condition for breakpoint ${::decimal}.*The program being debugged stopped while in a function called from GDB.*" \
 	"stop in condition function"
 
     gdb_test "continue" "Continuing.*" "finish condition evaluation"
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index c510ab25365..528e97bf099 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -9122,5 +9122,13 @@ gdb_caching_proc have_epilogue_line_info {
     }
 }
 
+# Return true if we are currently testing the 'remote' or
+# 'extended-remote' targets.
+proc gdb_is_remote_or_extended_remote_target {} {
+    return [target_info exists gdb_protocol]
+	   && ([target_info gdb_protocol] == "remote"
+	       || [target_info gdb_protocol] == "extended-remote")
+}
+
 # Always load compatibility stuff.
 load_lib future.exp
-- 
2.25.4