Fortran Common Blocks

["Knott, Martin" <martin at epc dot co dot uk>]

Hi 

I am currently attempting to generate Dwarf2 information for common blocks.
However, I am a little curious by the messages that DwarfDump produces:

<1><  123>      DW_TAG_subprogram
                DW_AT_decl_line             1
                DW_AT_decl_column           0
                DW_AT_decl_file             1
                DW_AT_sibling               <192>
                DW_AT_accessibility         DW_ACCESS_public
                DW_AT_name                  main.program
                DW_AT_type                  <115>
                DW_AT_prototyped            no
                DW_AT_high_pc               0x8048d20
                DW_AT_low_pc                0x8048c50
                DW_AT_external              yes(1)
*** DWARF CHECK: DW_TAG_common_block: tag-tree relation is not valid ***
<2><  159>      DW_TAG_common_block
                DW_AT_decl_line             6
                DW_AT_decl_column           0
                DW_AT_decl_file             1
                DW_AT_sibling               <191>
                DW_AT_declaration           yes(1)
                DW_AT_name                  acommon
*** DWARF CHECK: DW_TAG_variable: tag-tree relation is not valid ***
<3><  176>      DW_TAG_variable
                DW_AT_decl_line             6
                DW_AT_decl_column           0
                DW_AT_decl_file             1
                DW_AT_accessibility         DW_ACCESS_public
                DW_AT_name                  arr
                DW_AT_type                  <192>
                DW_AT_external              no

(I downloaded DwarfDump from http://reality.sgi.com/davea/objectinfo.html). 

The above output suggests that:
a) DW_TAG_common_block cannot be a child of DW_TAG_subprogram, and
b) DW_TAG_variable cannot be a child of DW_TAG_common_block.

I notice also that in the Dwarf2 draft spec the use of
DW_TAG_common_inclusion is mentioned in relation to DW_TAG_subprogram
entries.

Could anyone enlighten me as to how the standard envisages common blocks to
be handled, who the parent of a DW_TAG_common_block DIE is supposed to be,
and who its children can be?

Thanks
Martin Knott

Edinburgh Portable Compilers Ltd
17 Alva Street
Edinburgh
Scotland