[PATCH v2] of [PATCH v2 42/47] gdb_test_multiple: Anchor prompt match if -lbl

[Pedro Alves <pedro@palves.net>]

Hi!

On 2025-05-28 00:20, Pedro Alves wrote:
> On 2025-05-27 23:41, Pedro Alves wrote:
> 
> Somehow I didn't recall that we can define commands in the CLI with "define foo".  :-)
> 
> I think the best & simplest in this case is to do just that.  Like, put this in a gdb script (*):
> 
> define command
>   echo prefix \n
>   echo prefix foo\n
>   echo prefix bar\n
>   echo prefix \n
> end
> 
> then run the testcase with GDB as normal, load the script, and use gdb_test_multiple, all as usual.
> 
> I can take care of that.

I went ahead and did this.  Here's the new patch, now with a testcase, and a new commit log,
with a better explanation.

Let me know what you think of this one.

--- 8< ---
From d3a75f89b701d32958cc3f54642204054984c17c Mon Sep 17 00:00:00 2001
From: Pedro Alves <pedro@palves.net>
Date: Wed, 28 May 2025 10:40:46 +0100
Subject: [PATCH] gdb_test_multiple: Anchor prompt match if -lbl

The testcase added by this patch has a gdb_test_multiple call that
wants to match different lines of output that all have a common
prefix, and do different actions on each.  Instead of a single regular
expression with alternatives, its clearer code if the different
expressions are handled with different "-re", like so:

  gdb_test_multiple "command" "" -lbl {
     -re "^command(?=\r\n)" {
	 exp_continue
     }
     -re "^\r\nprefix foo(?=\r\n)" {
	 # some action
	 exp_continue
     }
     -re "^\r\nprefix bar(?=\r\n)" {
	 # some other action
	 exp_continue
     }
     -re "^\r\nprefix (?=\r\n)" {
	 # yet another action
	 exp_continue
     }
     -re "^\r\n$::gdb_prompt $" {
	 gdb_assert {$all_prefixes_were_seen} $gdb_test_name
     }
  }

Above, the leading anchors in the "^\r\nprefix..." matches are needed
to avoid too-eager matching due to the common prefix.  Without the
anchors, if the expect output buffer happens to contain at least:

  "\r\nprefix \r\nprefix foo\r\n"

... then the "prefix foo" pattern match inadvertently consumes the
first "prefix " line.

Without the anchor in the prompt match, like:

  -re "\r\n$::gdb_prompt $" {
      gdb_assert {$all_prefixes_were_seen} $gdb_test_name
  }

Or the equivalent:

  -re -wrap "" {
      gdb_assert {$all_prefixes_were_seen} $gdb_test_name
  }

... then if the expect buffer contains:

  "\r\nmeant-to-be-matched-by-lbl\r\nprefix foo\r\n$gdb_prompt "

... then the prompt regexp matches this, consuming the "prefix" line
inadvertently, and we get a FAIL.  The built-in regexp matcher for
-lbl doesn't get a chance to match the
"\r\nmeant-to-be-matched-by-lbl\r\n" part, because the built-in prompt
match appears first within gdb_test_multiple.

By adding the anchor to the prompt regexp, then we avoid that problem.

However, the same expect output buffer contents will still match the
built-in prompt match.  That is what is fixed by this patch.  It makes
it so that if -lbl is specified, the built-in prompt regexp has a
leading anchor.

Original idea for turning this into a gdb.testsuite/ testcase by Tom
de Vries <tdevries@suse.de>.

Change-Id: Ic2571ec793d856a89ee0d533ec363e2ac6036ea2
---
 .../gdb.testsuite/gdb_test_multiple-lbl.exp   | 84 +++++++++++++++++++
 .../gdb.testsuite/gdb_test_multiple-lbl.gdb   | 25 ++++++
 gdb/testsuite/lib/gdb.exp                     |  4 +-
 3 files changed, 112 insertions(+), 1 deletion(-)
 create mode 100644 gdb/testsuite/gdb.testsuite/gdb_test_multiple-lbl.exp
 create mode 100755 gdb/testsuite/gdb.testsuite/gdb_test_multiple-lbl.gdb

diff --git a/gdb/testsuite/gdb.testsuite/gdb_test_multiple-lbl.exp b/gdb/testsuite/gdb.testsuite/gdb_test_multiple-lbl.exp
new file mode 100644
index 00000000000..1ed352ddad7
--- /dev/null
+++ b/gdb/testsuite/gdb.testsuite/gdb_test_multiple-lbl.exp
@@ -0,0 +1,84 @@
+# Copyright 2025 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/>.
+
+# Test gdb_test_multiple -lbl, particularly with patterns that share a
+# common prefix.
+
+standard_testfile
+
+clean_restart
+
+gdb_test_no_output "source ${srcdir}/${subdir}/$testfile.gdb" \
+    "source gdb test script"
+
+set saw_prompt 0
+set saw_prefix 0
+set saw_command 0
+set saw_prefix_foo 0
+set saw_prefix_bar 0
+
+# #1 - We need anchors so that the "prefix foo" pattern below does not
+# match when the expect output buffer contains:
+#
+#  "\r\nprefix \r\n\prefix foo\r\n"
+#
+# #2 - We need an anchor on the prompt match as otherwise the prompt
+# regexp would match:
+#
+#  "\r\nmeant-to-be-matched-by-lbl-2\r\nprefix \r\n(gdb) "
+#
+# This test would fail if -lbl did not force the built-in prompt match
+# regexp to have an anchor as well, as without it, the built-in prompt
+# regexp would have the exact same issue as #2 above.
+
+gdb_test_multiple "command" "" -lbl {
+    -re "^command(?=\r\n)" {
+	verbose -log <COMMAND>
+	incr saw_command
+	exp_continue
+    }
+    -re "^\r\nprefix foo(?=\r\n)" {
+	verbose -log <PREFIX-FOO>
+	incr saw_prefix_foo
+	exp_continue
+    }
+    -re "^\r\nprefix bar(?=\r\n)" {
+	verbose -log <PREFIX-BAR>
+	incr saw_prefix_bar
+	exp_continue
+    }
+    -re "^\r\nprefix (?=\r\n)" {
+	verbose -log <PREFIX>
+	incr saw_prefix
+	exp_continue
+    }
+    -re "^\r\n$gdb_prompt $" {
+	verbose -log <PROMPT>
+	incr saw_prompt
+	pass $gdb_test_name
+    }
+}
+
+verbose -log "saw_command: $saw_command"
+verbose -log "saw_prefix_foo: $saw_prefix_foo"
+verbose -log "saw_prefix_bar: $saw_prefix_bar"
+verbose -log "saw_prefix: $saw_prefix"
+verbose -log "saw_prompt: $saw_prompt"
+
+gdb_assert {$saw_command == 1}
+gdb_assert {$saw_prefix_foo == 1}
+gdb_assert {$saw_prefix_bar == 1}
+gdb_assert {$saw_prefix == 3}
+gdb_assert {$saw_prompt == 1}
diff --git a/gdb/testsuite/gdb.testsuite/gdb_test_multiple-lbl.gdb b/gdb/testsuite/gdb.testsuite/gdb_test_multiple-lbl.gdb
new file mode 100755
index 00000000000..710c5e057ba
--- /dev/null
+++ b/gdb/testsuite/gdb.testsuite/gdb_test_multiple-lbl.gdb
@@ -0,0 +1,25 @@
+# Copyright 2025 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/>.
+
+define command
+  echo prefix \n
+  echo meant-to-be-matched-by-lbl-1\n
+  echo prefix foo\n
+  echo prefix bar\n
+  echo meant-to-be-matched-by-lbl-2\n
+  echo prefix \n
+  echo prefix \n
+  echo meant-to-be-matched-by-lbl-3\n
+end
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 0caa9cccd80..eefb6382a27 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -1127,6 +1127,7 @@ proc gdb_test_multiple { command message args } {
     global any_spawn_id
 
     set line_by_line 0
+    set lbl_anchor_re ""
     set prompt_regexp ""
     set prompt_anchor 1
     for {set i 0} {$i < [llength $args]} {incr i} {
@@ -1136,6 +1137,7 @@ proc gdb_test_multiple { command message args } {
 	    set prompt_regexp [lindex $args $i]
 	} elseif { $arg == "-lbl" } {
 	    set line_by_line 1
+	    set lbl_anchor_re "^"
 	} elseif { $arg == "-no-prompt-anchor" } {
 	    set prompt_anchor 0
 	} else {
@@ -1394,7 +1396,7 @@ proc gdb_test_multiple { command message args } {
 	    fail "$errmsg"
 	    set result -1
 	}
-	-re "\r\n$prompt_regexp" {
+	-re "${lbl_anchor_re}\r\n$prompt_regexp" {
 	    if {![string match "" $message]} {
 		fail "$message"
 	    }

base-commit: f601ffb52199a883f16df385b73a14e756b3e19a
-- 
2.49.0