Re: [pushed] [gdb/testsuite] Fix gdb.threads/dlopen-libpthread.exp for upstream glibc

[Simon Marchi <simark@simark.ca>]

On 1/11/23 04:17, Tom de Vries via Gdb-patches wrote:
> On 1/10/23 19:05, Simon Marchi wrote:
>>> Attached patch fixes things.
>>>
>>> WDYT?
>>>
>>> Thanks,
>>> - Tom
>>
>>
>> Here:
>>
>>> # We link the exec without -lpthread, but libpthread.so may already be loaded at main
>>> # due to LD_PRELOAD.
>>> set libpthread_maybe_preloaded 0
>>> set binfile [standard_output_file $executable]
>>> if { [has_dependency $binfile libpthread\\.so] == 1 } {
>>>      set libpthread_maybe_preloaded 1
>>> }
>>
>> Ok, so this works because ldd is influenced by LD_PRELOAD, I didn't
>> know.
>>
> 
> Yes, while lddtree is not, which had me confused for a while.
> 
>>>
>>> # We link the shlib with -lpthread, but since glibc 2.34 libpthread has been
>>> # merged with libc, so libpthread.so may not be a dependency.
>>> set libpthread_missing 0
>>> if { [has_dependency $binfile libpthread\\.so] == 0 } {
>>>      set libpthread_missing 1
>>> }
>>
>> The two has_dependency calls use $binfile.  Should one of them use
>> $binfile_lib?  The second one I think.
> 
> Yes, thanks for catching this.
> 
> I'll commit after another build & test cycle.

Hmm, I still see the failure.  I think the second has_dependency doesn't
work.  It returns 1 when it shouldn't, because of the
dlopen-libpthread.so.d line:

    output of ldd /home/smarchi/build/binutils-gdb/gdb/testsuite/outputs/gdb.threads/dlopen-libpthread/dlopen-libpthread.so is
            linux-vdso.so.1 (0x00007ffc809ee000)^M
            libc.so.6 => /home/smarchi/build/binutils-gdb/gdb/testsuite/outputs/gdb.threads/dlopen-libpthread/dlopen-libpthread.so.d/libc.so.6 (0x00007f0a5cf03000)^M
            /lib64/ld-linux-x86-64.so.2 (0x00007f0a5d132000)^M

This directory is created by build_executable_own_libs in
lib/prelink-support.exp (used by the test).

Tweaking the regexp to include a forward slash makes it work for me:

  diff --git a/gdb/testsuite/gdb.threads/dlopen-libpthread.exp b/gdb/testsuite/gdb.threads/dlopen-libpthread.exp
  index 134265ff470..c97e0284475 100644
  --- a/gdb/testsuite/gdb.threads/dlopen-libpthread.exp
  +++ b/gdb/testsuite/gdb.threads/dlopen-libpthread.exp
  @@ -68,14 +68,14 @@ if { !$have_probe } {
   # due to LD_PRELOAD.
   set libpthread_maybe_preloaded 0
   set binfile [standard_output_file $executable]
  -if { [has_dependency $binfile libpthread\\.so] == 1 } {
  +if { [has_dependency $binfile /libpthread\\.so] == 1 } {
       set libpthread_maybe_preloaded 1
   }

   # We link the shlib with -lpthread, but since glibc 2.34 libpthread has been
   # merged with libc, so libpthread.so may not be a dependency.
   set libpthread_missing 0
  -if { [has_dependency $binfile_lib libpthread\\.so] == 0 } {
  +if { [has_dependency $binfile_lib /libpthread\\.so] == 0 } {
       set libpthread_missing 1
   }

Simon