[Bug backtrace/29395] blockframe.c:79: internal-error: get_frame_block: Assertion `bl != NULL' failed.

["simark at simark dot ca" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29395

Simon Marchi <simark at simark dot ca> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |simark at simark dot ca

--- Comment #9 from Simon Marchi <simark at simark dot ca> ---
I dissected the debug info a bit while looking at what GDB is doing.  The
execution is stopped in this hierarchy, in /usr/bin/kicad:

0x0000057d: DW_TAG_compile_unit
              DW_AT_producer    ("GNU C++14 12.2.0 -march=x86-64 -mtune=generic
-g -g -O2 -O2 -std=c++14 -fno-plt -fexceptions -fstack-clash-protection
-fcf-protection=full -fPIE -fvisibility=hidden -fvisibility-inlines-hidden")
              DW_AT_language    (DW_LANG_C_plus_plus_14)
              DW_AT_name       
("/usr/src/debug/kicad/kicad/kicad/dialogs/dialog_template_selector_base.cpp")
              DW_AT_comp_dir    ("/usr/src/debug/kicad/build/kicad")
              DW_AT_ranges      (0x0000187d
... snip ...
              DW_AT_low_pc      (0x0000000000000000)
              DW_AT_stmt_list   (0x00000178)


0x00031917:   DW_TAG_subprogram
                DW_AT_specification     (0x00009a0c
"_ZNSt7__cxx1112basic_stringIwSt11char_traitsIwESaIwEE9_M_assignERKS4_")
                DW_AT_decl_file
("/usr/include/c++/12.2.0/bits/basic_string.tcc")
                DW_AT_decl_line (273)
                DW_AT_decl_column       (0x05)
                DW_AT_object_pointer    (0x0003193b)
                DW_AT_low_pc    (0x00000000002946d0)
                DW_AT_high_pc   (0x00000000002947c8)
                DW_AT_frame_base        (DW_OP_call_frame_cfa)
                DW_AT_call_all_calls    (true)
                DW_AT_sibling   (0x00031ecf)

0x00031961:     DW_TAG_lexical_block
                  DW_AT_ranges  (0x000017a0
                     [0x00000000002946f5, 0x0000000000294729)
                     [0x0000000000294750, 0x00000000002947c2))
                  DW_AT_sibling (0x00031ec1)

0x00031c77:       DW_TAG_inlined_subroutine
                    DW_AT_abstract_origin       (0x000327c8
"_ZNSt7__cxx1112basic_stringIwSt11char_traitsIwESaIwEE13_M_set_lengthEm")
                    DW_AT_entry_pc      (0x000000000029471d)
                    DW_AT_GNU_entry_view        (0x0000)
                    DW_AT_ranges        (0x00001846
                       [0x000000000029471d, 0x0000000000294729)
                       [0x00000000002947ac, 0x00000000002947b8))
                    DW_AT_call_file    
("/usr/include/c++/12.2.0/bits/basic_string.tcc")
                    DW_AT_call_line     (293)
                    DW_AT_call_column   (0x11)
                    DW_AT_sibling       (0x00031d4e)

0x00031cee:         DW_TAG_inlined_subroutine
                      DW_AT_abstract_origin     (0x0003290b
"_ZNKSt7__cxx1112basic_stringIwSt11char_traitsIwESaIwEE7_M_dataEv")
                      DW_AT_entry_pc    (0x0000000000294721)
                      DW_AT_GNU_entry_view      (0x0001)
                      DW_AT_ranges      (0x00001858
                         [0x0000000000294721, 0x0000000000294721)
                         [0x00000000002947ac, 0x00000000002947b8))
                      DW_AT_call_file  
("/usr/include/c++/12.2.0/bits/basic_string.h")
                      DW_AT_call_line   (268)
                      DW_AT_call_column (0x1d)
                      DW_AT_sibling     (0x00031d17)


get_frame_block calls get_frame_address_in_block_if_available, which returns
0x2947ab (actually, the relocated version of it, but I'm using the unrelocated
version here so it matches the debug info above).  This is because
get_frame_address_in_block_if_available returns "pc - 1".  This address falls
outside the block the frame is in, if you look at the last
DW_TAG_inlined_subroutine's ranges.  Another unrelated block is returned by
block_for_pc.  The value returned by frame_inlined_callees (which counts the
number of inlined frame using the frame_infos) doesn't match the expected
number of "inlined subroutine block" we see by going up the block tree, we
eventually reach the global block and try to get its superblock.

So I think that the root of the problem is get_frame_address_in_block not
returning the right thing.

In addition to checking that `gdb_assert (bl != NULL);`, I think that
get_frame_block should check that the block obtained from `bl->superblock ()`
isn't the global block nor the static block.  I think we always expect to reach
a block that comes from a DW_TAG_subprogram or more precise.

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