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

Guinevere Larsen
2025-04-09T18:25:58Z

The recently included gdb.base/dlmopen-ns-ids.exp test can sometimes
fail the call to get_integer_valueof when trying to check the namespace
ID of the fourth dlopened SO, for apparently no reason.

What's happening is that the call to get_first_so_ns doesn't necessarily
consume the GDB prompt, and so get_integer_valueof will see the prompt
immediately and not find the value the test is looking for.

To fix this, a call to gdb_test is added to the end of get_first_so_ns
to consume the prompt if it wasn't consumed by the previous
gdb_test_multiple call. If the namespace was found (and so ns is not
-1), we can guarantee that the prompt was not consumed.

I tried several other ways to solve that problem, but they each caused
different problems:
* using -wrap in the second block of the gdb_test_multiple resulted in
every call timing out
* reducing the output with a pattern on the "info shared" call and
adding -wrap caused the line to not be recognized
* using exp_continue caused the value of ns to be overwritten, returning
the last SO_NS, instead of the first

With all these problems, adding the gdb_test call seemed the least
fragile option.
---
gdb/testsuite/gdb.base/dlmopen-ns-ids.exp | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
index 03b7a527af5..5c65162d98f 100644
--- a/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
+++ b/gdb/testsuite/gdb.base/dlmopen-ns-ids.exp
@@ -45,7 +45,7 @@ proc get_first_so_ns {} {
-re "From\\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]+$::binfile_lib.*" {
+ -re "^$::hex\\s+$::hex\\s+\\\[\\\[($::decimal)\\\]\\\]\\s+\[^\r\n]+$::binfile_lib\r\n" {
set ns $expect_out(1,string)
}
-re "^$::gdb_prompt $" {
@@ -54,6 +54,14 @@ proc get_first_so_ns {} {
exp_continue
}
}
+ # Clear the prompt from the previous test, if it was not consumed.
+ # This can't be done in the previous test because we need to leave on
+ # the first occurrence of the library, otherwise we'll overwrite the
+ # namespace found, and just adding gdb_prompt to the end of the success
+ # case caused several timeouts.
+ if {$ns != -1} {
+ gdb_test -nopass "" ".*"
+ }
return $ns
}

base-commit: d8c3e4901650e35ddf5083f693b8a21b9d24fcc6
--
2.49.0