[v2,0/4] GDB support for DW_AT_trampoline

  Hi,

please find attached a series of patches that attempts to enable GDB to
handle the DW_AT_trampoline attribute on functions and inlined
functions.

DW_AT_trampoline can be emitted by the compiler for functions that are
compiler generated trampolines (e.g. wrapping other function calls).
In doing so, the compiler can specify a target as the value of
DW_AT_trampoline which the trampoline is wrapping.

This series enables GDB to recognize the DW_AT_trampoline and store the
target for a given function.  Patch 3 adapts GDB's stepping behavior
when dealing with trampolines and attempts to - by default - hide these
trampolines from the user.  When about to step into a trampoline,
instead, GDB will try and step through the trampoline and directly
towards the target.  Patch 4 in V2 now skip trampoline frames
in the stack for printing or finish command.  A new setting has been
introduced to turn off this modified stepping behavior or printing of stack
for trampolines.

The motivation for these patches comes from ifx which emits the
attribute for some of its compiler generated functions.  As I do not
know of any other compiler (especially gcc/gfortran) emitting
DW_AT_trampoline, I added a gdb.dwarf2 test to this series in order to
test the trampoline handling within GDB.

Changes since V1:
  * Skip trampoline frames in the stack for printing or finish
    command.
  * Code reviews related changes:
        - Removed Changelog entries in commit messages.
        - Removed minimum symbol address search and addtional section
          offset for trampolines during symbol read.
        - Fix typo and improve description for option
          "skip-trampoline-functions".
        - Handling of data offset for trampoline target address is removed
          from dwarf reader.
        - Update trampoline function type bitfield handling in func_type
          structure.

V1 series of patches can be found here:
https://sourceware.org/pipermail/gdb-patches/2022-July/190566.html

No regression seen on testing unix/unix32/gdbserver/gdbserver-extended
test configurations for these changes using Ubuntu 18.

Thanks & Best Regards,
Abdul Basit Ijaz

Abdul Basit Ijaz (1):
  gdb: Skip trampoline frames in the stack for printing or finish
    command.

Nils-Christian Kempke (3):
  gdb, dwarf: add support for DW_AT_trampoline in DWARF reader
  gdb/symtab: add lookup for trampoline functions
  gdb/infrun: handle stepping through functions with DW_AT_trampoline

 gdb/NEWS                                      |  14 +
 gdb/doc/gdb.texinfo                           |  46 ++++
 gdb/dwarf2/read.c                             |  43 ++-
 gdb/gdbtypes.c                                |  35 ++-
 gdb/gdbtypes.h                                | 103 +++++++-
 gdb/infcmd.c                                  |  14 +
 gdb/infrun.c                                  |  81 +++++-
 gdb/infrun.h                                  |  10 +
 gdb/stack.c                                   |   8 +
 gdb/symtab.c                                  |  80 ++++++
 gdb/symtab.h                                  |  19 ++
 .../gdb.dwarf2/dw2-function-trampolines.c     |  80 ++++++
 .../gdb.dwarf2/dw2-function-trampolines.exp   | 245 ++++++++++++++++++
 gdb/testsuite/gdb.fortran/func-trampoline.exp |  69 +++++
 gdb/testsuite/gdb.fortran/func-trampoline.f90 |  39 +++
 .../gdb.fortran/mixed-lang-stack.exp          |  10 +-
 16 files changed, 882 insertions(+), 14 deletions(-)
 create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-function-trampolines.c
 create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-function-trampolines.exp
 create mode 100644 gdb/testsuite/gdb.fortran/func-trampoline.exp
 create mode 100644 gdb/testsuite/gdb.fortran/func-trampoline.f90