https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78212
John DelSignore <jdelsignore at perforce dot com> changed:
What |Removed |Added
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CC| |jdelsignore at perforce dot com
--- Comment #2 from John DelSignore <jdelsignore at perforce dot com> ---
A user recently reported that TotalView could not print the value of Fortran
variable length character strings in user defined types. Here is the test
program they submitted, which is similar to the one contained in this bug
report:
program test
implicit none
type my_type
character(:), allocatable :: str
end type my_type
type (my_type) a
character(:), allocatable :: t
allocate (character(10):: t)
t = 'abc'
a%str = 'xyz'
print *, 't="', t, '", a%str="', a%str, '"'
end program test
The DWARF for "t" is OK, but the DWARF for field "str" in "my_type" is not.
The GNU Fortran (gfortran) compiler does not generate a DWARF string length
attribute for the string type.
Dumping the DWARF for gfortran 10.2.0, we see:
<1><2e>: Abbrev Number: 2 (DW_TAG_structure_type)
<2f> DW_AT_name : (indirect string, offset: 0x0): my_type
<33> DW_AT_byte_size : 16
<34> DW_AT_decl_file : 1
<35> DW_AT_decl_line : 4
<36> DW_AT_sibling : <0x55>
<2><3a>: Abbrev Number: 3 (DW_TAG_member)
<3b> DW_AT_name : str
<3f> DW_AT_decl_file : 1
<40> DW_AT_decl_line : 7
<41> DW_AT_decl_column : 37
<42> DW_AT_type : <0x57>
<46> DW_AT_data_member_location: 0
<2><47>: Abbrev Number: 4 (DW_TAG_member)
<48> DW_AT_name : (indirect string, offset: 0x188): _str_length
<4c> DW_AT_decl_file : 1
<4d> DW_AT_decl_line : 4
<4e> DW_AT_decl_column : 12
<4f> DW_AT_type : <0x5d>
<53> DW_AT_data_member_location: 8
<1><57>: Abbrev Number: 6 (DW_TAG_pointer_type)
<58> DW_AT_byte_size : 8
<59> DW_AT_type : <0x55>
<1><55>: Abbrev Number: 5 (DW_TAG_string_type)
Member "str" is at offset 0 in the structure and has a type that
references DIE <57>.
DIE <57> is a pointer type, which isn't the correct way of handling
Fortran, but TotalView is smart enough to automatically dereference pointer
types in Fortran codes. The target of the pointer type is a reference
to DIE <55>.
DIE <55> is a string type, but it does not contain an attribute that
provides the string length, which I think is a compiler bug.
The compiler DOES generate the correct DWARF string type DIE for "t",
which is:
<2><f9>: Abbrev Number: 12 (DW_TAG_variable)
<fa> DW_AT_name : t
<fc> DW_AT_decl_file : 1
<fd> DW_AT_decl_line : 10
<fe> DW_AT_decl_column : 32
<ff> DW_AT_type : <0x10e>
<103> DW_AT_location : 2 byte block: 91 68 (DW_OP_fbreg: -24)
<1><10e>: Abbrev Number: 6 (DW_TAG_pointer_type)
<10f> DW_AT_byte_size : 8
<110> DW_AT_type : <0x107>
<1><107>: Abbrev Number: 14 (DW_TAG_string_type)
<108> DW_AT_string_length: 5 byte block: 99 ee 0 0 0 (DW_OP_call4:
<0xee>)
<2><ee>: Abbrev Number: 13 (DW_TAG_variable)
<ef> DW_AT_name : .t
<f2> DW_AT_type : <0x5d>
<f6> DW_AT_artificial : 1
<f6> DW_AT_location : 2 byte block: 91 60 (DW_OP_fbreg: -32)
Notice that the compiler generates a string type with a string length
attribute, which is a reference to an artificial variable that holds
the length of the string.
I think that DWARF 5 can support this by generating an string length attribute
that is an exprloc containing an operation that pushes the object address and
adds the offset to the length field.
