[Bug c++/41921] Cross language don't work with typedef unnamed structs

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2009-11-03 11:46 -------
The C++ FE for

extern "C" { typedef struct {} CvImage; }

creates

 <record_type 0x7ffff6f3f790 CvImage type_5 QI
    size <integer_cst 0x7ffff7ed5180 type <integer_type 0x7ffff7eea0b0
bit_size_type> constant 8>
    unit size <integer_cst 0x7ffff7ed51b0 type <integer_type 0x7ffff7eea000
long unsigned int> constant 1>
    align 8 symtab 0 alias set -1 canonical type 0x7ffff6f3f790
    fields <type_decl 0x7ffff6f3a6c0 ._0 type <record_type 0x7ffff6f3f790
CvImage>
        nonlocal decl_4 VOID file t1.C line 2 col 20
        align 1 context <record_type 0x7ffff6f3f790 CvImage>
       >
    full-name "struct CvImage"
    X() X(constX&) this=(X&) n_parents=0 use_template=0 interface-unknown
    chain <type_decl 0x7ffff6f3a600 ._0>>

thus, a named type.  The C frontend generates a named type with the
main-variant being an unnamed type.  The C++ frontend also assigns
different sizes to it.  C FE variant:

 <record_type 0x7ffff6eeabb0 CvImage type_0 BLK
    size <integer_cst 0x7ffff7ed5d80 type <integer_type 0x7ffff7ee70b0
bit_size_type> constant 0>
    unit size <integer_cst 0x7ffff7ed50f0 type <integer_type 0x7ffff7ee7000
long unsigned int> constant 0>
    align 8 symtab 0 alias set -1 canonical type 0x7ffff6eeab00
    chain <type_decl 0x7ffff6efb000 D.1607>>

and its main-variant (which is also its canonical type):

 <record_type 0x7ffff6eeab00 type_0 BLK
    size <integer_cst 0x7ffff7ed5d80 type <integer_type 0x7ffff7ee70b0
bit_size_type> constant 0>
    unit size <integer_cst 0x7ffff7ed50f0 type <integer_type 0x7ffff7ee7000
long unsigned int> constant 0>
    align 8 symtab 0 alias set -1 canonical type 0x7ffff6eeab00
    chain <type_decl 0x7ffff6efb000 D.1607>>


While we could try hard to workaround this in LTO I think this is a
C++ frontend bug.  extern "C" should cause it to behave like the C
frontend.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|rguenth at gcc dot gnu dot  |unassigned at gcc dot gnu
                   |org                         |dot org
             Status|ASSIGNED                    |NEW
          Component|lto                         |c++
           Keywords|                            |lto


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41921