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

[Tom de Vries <tdevries@suse.de>]

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On 5/19/25 15:23, Pedro Alves wrote:
> I wrote a test like this:
> 
>      gdb_test_multiple "command" "" -lbl {
>         -re "^\r\nprefix foo(?=\r\n)" {
>             exp_continue
>         }
>         -re "^\r\nprefix bar(?=\r\n)" {
>             exp_continue
>         }
>         -re "^\r\prefix (?=\r\n)" {

Hi Pedro,

Missing n in "\r\n".

>             exp_continue
>         }
>         -re "^\r\n$::gdb_prompt $" {
>         	   pass $gdb_test_name
>         }
>      }
> 
> Anchors are needed in my case to avoid too-eager matching due to the
> common prefix. 
I'm not saying you don't need anchors, maybe you do or maybe you don't, 
but I don't understand how a common prefix is a reason to need one.

Also, if you need anchors, you need to match the command as well, so you 
need a -re "^command(?=\r\n)" clause.

> The intent is for the prompt match above to override the built-in
> prompt match.  However, it doesn't and the test fails with output like
> this:
> 
>    (gdb) command
>    prefix foo
>    prefix bar
>    meant-to-be-matched-by-lbl
>    (gdb)
> 
> That's because the built-in match for the prompt matches before the
> -lbl pattern for this expect buffer:
> 
>    \r\nmeant-to-be-matched-by-lbl\r\n(gdb)
>

You can fix that by dropping the anchor and using "\r\n$::gdb_prompt $" 
instead.  Even more simple, use -wrap "".

> This this by anchoring the built-in prompt match if -lbl was
> requested.
> 

This might be a good idea indeed.

FWIW, the intent of -lbl was to handle except buffers overflows, so the 
-lbl pattern is meant to match lines in absence of a prompt.

But AFAIU, your patch will make matching more predictable, so that's a 
good thing.

I created a mockup test-case to emulate the case you describe above. 
I've left the anchoring in place for the prefix lines, but for the gdb 
output printed by gdb.sh, it doesn't look necessary. [ The test-case has 
hardcoded paths in it. ]

Thanks,
- Tom


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From 91363128b5918a16a8426ca31b43927004d1535d Mon Sep 17 00:00:00 2001
From: Tom de Vries <tdevries@suse.de>
Date: Wed, 21 May 2025 17:13:55 +0200
Subject: [PATCH] try

---
 .../gdb.testsuite/gdb-test-multiple.exp       | 25 ++++++++++
 gdb/testsuite/gdb.testsuite/gdb.sh            | 47 +++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 gdb/testsuite/gdb.testsuite/gdb-test-multiple.exp
 create mode 100755 gdb/testsuite/gdb.testsuite/gdb.sh

diff --git a/gdb/testsuite/gdb.testsuite/gdb-test-multiple.exp b/gdb/testsuite/gdb.testsuite/gdb-test-multiple.exp
new file mode 100644
index 00000000000..ac0674ef20f
--- /dev/null
+++ b/gdb/testsuite/gdb.testsuite/gdb-test-multiple.exp
@@ -0,0 +1,25 @@
+set GDB $srcdir/$subdir/gdb.sh
+clean_restart
+
+gdb_test_multiple "command" "" -lbl {
+    -re "^command(?=\r\n)" {
+	verbose -log <COMMAND>
+	exp_continue
+    }
+    -re "^\r\nprefix foo(?=\r\n)" {
+	verbose -log <PREFIX-FOO>
+	exp_continue
+    }
+    -re "^\r\nprefix bar(?=\r\n)" {
+	verbose -log <PREFIX-BAR>
+	exp_continue
+    }
+    -re "^\r\nprefix (?=\r\n)" {
+	verbose -log <PREFIX>
+	exp_continue
+    }
+    -re -wrap "" {
+	verbose -log "<PROMPT>"
+	pass $gdb_test_name
+    }
+}
diff --git a/gdb/testsuite/gdb.testsuite/gdb.sh b/gdb/testsuite/gdb.testsuite/gdb.sh
new file mode 100755
index 00000000000..9c358f1a204
--- /dev/null
+++ b/gdb/testsuite/gdb.testsuite/gdb.sh
@@ -0,0 +1,47 @@
+#!/bin/sh
+
+while [ $# -gt 0 ]; do
+    case $1 in
+	--version)
+	    echo "gdb.sh"
+	    exit 0
+	    ;;
+	*)
+	    ;;
+    esac
+
+    shift
+done
+
+while true; do
+    echo -n "(gdb) "
+    read line
+
+    if [ "$line" = "set height 0" ]; then
+	continue
+    fi
+
+    if [ "$line" = "set width 0" ]; then
+	continue
+    fi
+
+    if [ "$line" = "dir" ]; then
+	echo -n "Reinitialize source path to empty? (y or n) "
+	read response
+	echo 'Source directories searched: $cdir:$cwd'
+	continue
+    fi
+
+    if [ "$line" = "dir /data/vries/gdb/src/gdb/testsuite/gdb.testsuite" ]; then
+	echo "Source directories searched: /data/vries/gdb/src/gdb/testsuite/gdb.testsuite:$cdir:$cwd"
+	continue
+    fi
+
+    if [ "$line" = "command" ]; then
+	echo "prefix foo"
+	echo "prefix bar"
+	for n in $(seq 1 1); do
+	    echo "meant-to-be-matched-by-lbl-$n"
+	done
+    fi
+done

base-commit: 14dd98b0f7f04d25bc7bc63de3ab958bdd51641d
-- 
2.43.0