Re: [PATCH] gdb/testsuite: fix gdb.base/dlmopen-ns-ids.exp racy test

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

On 4/10/25 06:40, Tom de Vries wrote:
> On 4/9/25 20:25, Guinevere Larsen wrote:
>> * using exp_continue caused the value of ns to be overwritten, returning
>>    the last SO_NS, instead of the first
> 
> Hi Gwen,
> 
> my guess is that this is the right solution, and that you can just check 
> for $ns == -1 to make sure only the first value is picked.

I tried this out, and got it working, after fixing the following.

There is a problem with the gdb_test_multiple.

It uses -lbl, which is the style of processing one line at a time, with 
\r\n at the start, and (?=\r\n) at the end, which matches but not 
consumes it (lookahead), always leaving an \r\n at the start of the next 
line.

This matches what -wrap (which is based on gdb_test) does which requires 
an \r\n before the prompt.

I got the test-case working using:
...
diff --git a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp 
b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
index 03b7a527af5..d3584a0a402 100644
--- a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
+++ b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
@@ -42,17 +42,17 @@ if { [build_executable "failed to build" $testfile 
$srcfile \
  proc get_first_so_ns {} {
      set ns -1
      gdb_test_multiple "info sharedlibrary" "get SO namespace" -lbl {
-	-re "From\\s+To\\s+\(NS\\s+\)?Syms\\s+Read\\s+Shared Object Library\r\n" {
+	-re "\r\nFrom\\s+To\\s+\(NS\\s+\)?Syms\\s+Read\\s+Shared Object 
Library(?=\r\n)" {
  	    exp_continue
  	}
-	-re 
"^$::hex\\s+$::hex\\s+\\\[\\\[($::decimal)\\\]\\\]\\s+\[^\r\n]+$::binfile_lib.*" 
{
-	    set ns $expect_out(1,string)
-	}
-	-re "^$::gdb_prompt $" {
-	}
-	-re "^\[^\r\n\]+\r\n" {
+	-re 
"\r\n$::hex\\s+$::hex\\s+\\\[\\\[($::decimal)\\\]\\\]\\s+\[^\r\n]+${::binfile_lib}(?=\r\n
)" {
+	    if { $ns == -1 } {
+		set ns $expect_out(1,string)
+	    }
  	    exp_continue
  	}
+	-re -wrap "" {
+	}
      }
      return $ns
  }
...

I also think that binfile_lib needs to be wrapped in string_to_regexp.

Thanks,
- Tom