Re: Unable to access fields of a record type in some cases

[David Malcolm <dmalcolm at redhat dot com>]

On Mon, 2016-09-19 at 10:09 +0200, Richard Biener wrote:
> On Mon, Sep 19, 2016 at 3:52 AM, Swati Rathi <
> swatirathi@cse.iitb.ac.in> wrote:
> > Hello,
> > 
> > We want to fetch fields of a record type from the formal arguments
> > of a
> > function.
> > For a RECORD_TYPE, we fetch the fields using TYPE_FIELDS.
> > 
> > In the program 471.omnetpp (from the SPEC CPU2006 benchmark suite),
> > we
> > encountered a case where we were not able to access the fields.
> > Below is the
> > dump of the same record type showing different output in different
> > functions. We are not able to access fields of the record type for
> > the first
> > case.
> > 
> > Can you tell us the reason for different type nodes?
> 
> The first is a pointer to an incomplete struct like what you'd get
> from
> 
>  struct Foo *p;
> 
> without a definition of struct Foo.
> 
> > Also can you suggest an approach to solve our problem.
> 
> Sorry, no.

Are you running this from a gcc plugin?

If so, maybe your code is running too early, before the record type is
fully parsed?  If that's the case, you could try running your code late
r.  Presumably you're hooking in to a callback, or registering a new
pass relative to a pre-existing one.  You could try hooking onto a
different callback, or running the pass later.  

Hope this is helpful
Dave


> Richard.
> 
> > -------------------------------------------------------------------
> > ------------------------
> > Pointer declared as "struct cMessage *" is a parameter in one
> > function.
> > Below is the dump of node "struct cMessage *".
> > 
> > <pointer_type 0x2b8fad7baa80
> >     type <record_type 0x2b8fad7bab28 cMessage VOID
> >         align 8 symtab 0 alias set -1 canonical type 0x2b8faa800690
> > context
> > <translation_unit_decl 0x2b8fad76e958 D.82130>
> >         pointer_to_this <pointer_type 0x2b8fad7baa80> chain
> > <type_decl
> > 0x2b8fad7b3730 cMessage>>
> >     unsigned DI
> >     size <integer_cst 0x2b8faa6c1ec0 type <integer_type
> > 0x2b8faa6d20a8
> > bitsizetype> constant 64>
> >     unit size <integer_cst 0x2b8faa6c1ee0 type <integer_type
> > 0x2b8faa6d2000
> > sizetype> constant 8>
> >     align 64 symtab 0 alias set -1 canonical type 0x2b8faa800e70
> >     pointer_to_this <pointer_type 0x2b8fad7d9000>>
> > 
> > 
> > Another pointer also declared as "struct cMessage *" is a parameter
> > in
> > second function. Below is the dump of node "struct cMessage *".
> > 
> > <pointer_type 0x2b8faa834150
> >     type <record_type 0x2b8faa82e1f8 cMessage addressable needs
> > -constructing
> > BLK
> >         size <integer_cst 0x2b8faa8186c0 constant 1408>
> >         unit size <integer_cst 0x2b8faa818720 constant 176>
> >         align 64 symtab 0 alias set -1 canonical type
> > 0x2b8faa834c78
> >         fields <field_decl 0x2b8faa826850 D.2814 type <record_type
> > 0x2b8faa819150 cObject>
> >             ignored BLK file omnet_include/cmessage.h line 84 col
> > 15
> >             size <integer_cst 0x2b8faa6d4620 constant 448>
> >             unit size <integer_cst 0x2b8faa7f0620 constant 56>
> >             align 64 offset_align 128
> >             offset <integer_cst 0x2b8faa6c1f00 constant 0>
> >             bit offset <integer_cst 0x2b8faa6c1f60 constant 0>
> > context
> > <record_type 0x2b8faa82e1f8 cMessage> chain <field_decl
> > 0x2b8faa8268e8
> > swati_test>> context <translation_unit_decl 0x2b8faa6dcf18 D.2350>
> >         pointer_to_this <pointer_type 0x2b8faa82e2a0>
> > reference_to_this
> > <reference_type 0x2b8fab219c78> chain <type_decl 0x2b8faa82b678
> > cMessage>>
> >     public unsigned DI
> >     size <integer_cst 0x2b8faa6c1ec0 type <integer_type
> > 0x2b8faa6d20a8
> > bitsizetype> constant 64>
> >     unit size <integer_cst 0x2b8faa6c1ee0 type <integer_type
> > 0x2b8faa6d2000
> > sizetype> constant 8>
> >     align 64 symtab 0 alias set -1 canonical type 0x2b8faa800e70
> >     pointer_to_this <pointer_type 0x2b8faa8a3d20>>
> > 
> > -------------------------------------------------------------------
> > ------------------------
> > 
> > Thank you.
> > 
> > Regards,
> > Swati