Bug 1905701

+++ This bug was initially created as a clone of Bug #1905687 +++

Originally reported/triaged by Andrew Dinn:

I have run up against a problem with the versions of gdb that are out in the field that relates to the use of data_location properties on DWARF class/struct info records. I need to use this DWARF feature in order to fully implement Java debuginfo for GraalVM native Java apps. The data_location attribute is needed to ensure that Java oops (typed as DWARF pointer types which reference the underlying class/struct data) are adjusted from a Java-specific encoding of the address to a direct memory pointer before gdb dereferences the oop to locate the underlying data.

 - In one mode of image generation oops are addresses modulo extra tag info in the bottom 3 bits so a locexpr describes how to mask off the relevant bits.

 - In another mode of image generation oops are offsets from a heap base held in a register so a locexpr describes how to fetch the relevant register value and add it to the oop (offset).

The data_location attribute on the target object provides the necessary locexpr.

My problem is not to do with the conversion itself. That all works fine. It goes wrong when I ask gdb to print the relevant object data (see example after sig). The value that gets inserted into the history has an unresolved dynamic type and this trips an assert .

This problem should be caught and dealt with before the value is passed to the print code and indeed it has been fixed in gdb 10.1. The patch is detailed in the asssociated ChangeLog as follows:

2020-07-25  Andrew Burgess  <andrew.burgess>

    PR fortran/23051
    PR fortran/26139
    * valops.c (value_ind): Pass address to
    readjust_indirect_value_type.
    * value.c (readjust_indirect_value_type): Make parameter
    non-const, and add extra address parameter.  Resolve original type
    before using it.
    * value.h (readjust_indirect_value_type): Update function
    signature and comment.

--- Additional comment from Keith Seitz on 2020-12-08 20:30:10 UTC ---



--- Additional comment from Keith Seitz on 2020-12-08 20:31:00 UTC ---

Testing patch.