tree f93f75fc0a78464b07d9f046e6fe45e96fac6910
parent 903ea49d4780084fe8e6aac38e326cf29281eb08
author Simon Marchi <simon.marchi@efficios.com> 1754508696 -0400
committer Simon Marchi <simon.marchi@efficios.com> 1755190160 -0400

gdb/dwarf: clear per_bfd::num_{comp,type}_units on error

Commit bedd6a7a44 ("gdb/dwarf: track compilation and type unit count")
causes this internal error:

    $ ./gdb -nx -q --data-directory=data-directory testsuite/outputs/gdb.dwarf2/debug-names-duplicate-cu/debug-names-duplicate-cu -ex "save gdb-index -dwarf-5 /tmp" -batch

    warning: Section .debug_names has incorrect number of CUs in CU table, ignoring .debug_names.
    /home/smarchi/src/binutils-gdb/gdb/dwarf2/index-write.c:1454: internal-error: write_debug_names: Assertion `comp_unit_counter == per_bfd->num_comp_units' failed.

This is visible when running this test:

    $ make check TESTS="gdb.dwarf2/debug-names-duplicate-cu.exp" RUNTESTFLAGS="--target_board=cc-with-debug-names"
    ...
    Running /home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.dwarf2/debug-names-duplicate-cu.exp ...
    gdb compile failed, warning: Section .debug_names has incorrect number of CUs in CU table, ignoring .debug_names.
    /home/smarchi/src/binutils-gdb/gdb/dwarf2/index-write.c:1454: internal-error: write_debug_names: Assertion `comp_unit_counter == per_bfd->num_comp_units' failed.
    ...
                    === gdb Summary ===

    # of untested testcases         1

However, it's easy to miss because it only causes an "UNTESTED" to be
recorded, not a FAIL or UNRESOLVED.  This is because the problem happens
while trying to create the .debug_names index, as part of the test case
compilation.

The problem is: when we bail out from using .debug_names because we
detect it is inconsistent with the units in .debug_info, we clear
per_bfd->all_units, to destroy all units previously created, before
proceeding to read the units with an index.  However, we don't clear
per_bfd->num_{comp,type}_units.  As a result, per_bfd->all_units
contains one unit, while per_bfd->num_comp_units is 2.  Whenever we
clear per_bfd->all_units, we should also clear
per_bfd->num_{comp,type}_units.

While at it, move this logic inside a scoped object.

I added an assertion in finalize_all_units to verify that the size of
per_bfd->all_units equals per_bfd->num_comp_units +
per_bfd->num_type_units.  This makes the problem (if omitting the fix)
visible when running gdb.dwarf2/debug-names-duplicate-cu.exp with the
unix (default) target board:

    ERROR: Couldn't load debug-names-duplicate-cu into GDB (GDB internal error).
    FAIL: gdb.dwarf2/debug-names-duplicate-cu.exp: find index type (GDB internal error)
    FAIL: gdb.dwarf2/debug-names-duplicate-cu.exp: find index type, check type is valid

                    === gdb Summary ===

    # of expected passes            1
    # of unexpected failures        2
    # of unresolved testcases       1

I considered changing the code to build a local vector of units first,
then move it in per_bfd->all_units on success, that would avoid having
to clean it up on error.  I did not do it because it's a much larger
change, but we could consider it.

Change-Id: I49bcc0cb4b34aba3d882b27c8a93c168e8875c08
Approved-By: Tom Tromey <tom@tromey.com>