GDB system pretty printers for new objfiles not available

GDB system pretty printers don't work if they are declared in autoloaded Python scripts and the objfiles are loaded dynamically. An example to reproduce is this scenario including the rr debugger.

Steps to reproduce:

1. in GDB settings ("Tools" -> "Options" -> "Debugger" -> "GDB", set these settings:
   1. enable "Load system GDB pretty printers"
   2. set these additional startup commands:

      1. set auto-load safe-path /
         set sysroot /
         set solib-search-path /tmp/gdb-pretty-printer-objfile-sample/
         

1. extract the attached sample project "gdb-pretty-printer-objfile-sample.zip" into /tmp/ and change into the directory /tmp/gdb-pretty-printer-objfile-sample
2. build using bear, so that a compile_commands.json is created:

   1. bear -- make
      

1. record a run of the test program using rr

   1. rr record ./test
      

1. replay using rr (providing debugging server to connect to later):

1. 1. rr replay -s 50505 -k
      

1. load the project into Qt Creator using the compile_commands.json file created in step 3 (experimental CompilationDatabaseProjectManager" plugin must be enabled)
2. set breakpoint in line 5 of py-autoloaded-pretty-printers-in-newobjfile-event-main.cc (return statement)
3. start debugging by connecting to the debugging server provided by rr/gdb (s. step 5):
   1. "Debug" -> "Start debugging" -> "Attach to running debug server"
   2. in the dialog, make sure that these are set:
      1. Server port: 50505
      2. executable: /tmp/gdb-pretty-printer-objfile-sample/test
   3. press OK
4. check how value for variable "test" is displayed in the locals view when reaching the breakpoint

Actual result: just a pointer value is shown

Expected result: The value as printed by the pretty-printed should be used, as is the case when directly running the program in GDB (i.e. not with rr and the debug server) or when using plain GDB instead of Qt Creator: "MyClassTestLib object, id: 1"

Plain GDB:

(gdb) p test
$1 = "MyClassTestLib object, id: 1"

Further information: I have analyzed this a bit, will add more information in follow-up comments.