Re: Debugging the tree object constructed by cp_parser

[Stan Srednyak <stan.sredn@gmail.com>]

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Hi David,

Thanks for your suggestion. I really appreciate it.

But I would like to modify the trees as they are constructed. So the first
step is to understand how to print them out ( using debug_tree() or even
printf()) from inside cp_parser.cc.

I think it is a reasonable question: where are the ASTs ( or parts that
correspond to translation units, or something smaller) stored as they are
constructed by the parser.

thanks,
sincerely yours,
Stan

On Mon, Dec 4, 2023 at 10:46 AM David Malcolm <dmalcolm@redhat.com> wrote:

> On Mon, 2023-12-04 at 10:09 -0500, Stan Srednyak wrote:
> > Hi David, thanks for your email. I really appreciate it.
> >
> > Your notes are certainly of help, but I also had a specific question:
> > how
> > to access the trees as they are being constructed by the front end.
> > Do you
> > have an answer to this?
>
> You could try putting a breakpoint on "make_node", and then
> conditionalizing it so it only fires when code ==
> TRANSLATION_UNIT_DECL:
>
> (gdb) break make_node
> Breakpoint 5 at 0x1675250: file ../../src/gcc/tree.cc, line 1188.
>
> (gdb) cond 5 code==TRANSLATION_UNIT_DECL
>
> (gdb) run
> The program being debugged has been started already.
> Start it from the beginning? (y or n) y
>
> [...snip...]
>
> Breakpoint 5, make_node (code=TRANSLATION_UNIT_DECL) at
> ../../src/gcc/tree.cc:1188
> 1188    {
>
> (gdb) bt
> #0  make_node (code=TRANSLATION_UNIT_DECL) at
> ../../src/gcc/tree.cc:1188
> #1  0x0000000001675aae in build_decl (loc=0,
> code=TRANSLATION_UNIT_DECL, name=<identifier_node 0x7fffea664b00
> /tmp/t.c>, type=<tree 0x0>)
>     at ../../src/gcc/tree.cc:5379
> #2  0x000000000169644c in build_translation_unit_decl (name=<optimized
> out>) at ../../src/gcc/tree.cc:5432
> #3  0x0000000000b1e181 in cxx_init_decl_processing () at
> ../../src/gcc/tree.h:3749
> #4  0x0000000000b6b904 in cxx_init () at ../../src/gcc/cp/lex.cc:336
> #5  0x0000000000a4e23a in lang_dependent_init (name=0x34bd820
> "/tmp/t.c") at ../../src/gcc/toplev.cc:1838
> #6  do_compile () at ../../src/gcc/toplev.cc:2136
> #7  toplev::main (this=this@entry=0x7fffffffdd6e, argc=<optimized out>,
> argc@entry=22, argv=<optimized out>, argv@entry=0x7fffffffde78)
>     at ../../src/gcc/toplev.cc:2307
> #8  0x0000000000a502f5 in main (argc=22, argv=0x7fffffffde78) at
> ../../src/gcc/main.cc:39
>
>
> Dave
>
> >
> > I looked into GCC internals docs. The section on the front  end (sec
> > 5) is
> > wonderfully concise, of course, but it does not answer this question.
> > Do
> > you know any sources where this is documented?
> >
> > best regards,
> > Stan
> >
> > On Sun, Dec 3, 2023 at 1:00 PM David Malcolm <dmalcolm@redhat.com>
> > wrote:
> >
> > > On Sat, 2023-12-02 at 17:41 -0500, Stan Srednyak via Gcc wrote:
> > > > Dear GCC community,
> > > >
> > > > I am assigned the task to debug the trees as being produced by
> > > > the
> > > > cp_parser. I was able to print some of the trees using the
> > > > debug_tree()
> > > > function. But I am still confused as to where is the tree object
> > > > that
> > > > corresponds to the translation unit being parsed. There is no
> > > > such
> > > > field in
> > > > cp_parser, and in the few tiers of functions calls starting from
> > > > parse_file() function that I followed so far, I was not able to
> > > > find
> > > > any
> > > > variable remotely similar to the AST of functions/structs etc.
> > > > that
> > > > must be
> > > > constructed by this great piece of software. I would very much
> > > > appreciate
> > > > any explanation from the great experts in gcc on this mailing
> > > > list. I
> > > > posted a thread at gcc-help, but apparently it is too obvious of
> > > > a
> > > > question
> > > > to be addressed there.
> > >
> > > Hi Stan
> > >
> > > FWIW I've written some notes on debugging GCC:
> > > https://gcc-newbies-guide.readthedocs.io/en/latest/debugging.html
> > >
> > > and in particular you might find the following useful:
> > >
> > >
> https://gcc-newbies-guide.readthedocs.io/en/latest/debugging.html#how-do-i-find-where-a-particular-tree-was-created
> > >
> > > Hope this is helpful
> > > Dave
> > >
> > >
>
>