[Bug 460894] Review Request: ocsigen - Web programming framework

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https://bugzilla.redhat.com/show_bug.cgi?id=460894





--- Comment #10 from Richard W.M. Jones <rjones at redhat.com>  2009-01-14 07:19:58 EDT ---
(In reply to comment #9)
> > Debuginfo isn't really that useful for OCaml programs, since
> > gdb doesn't know about OCaml.  So you end up having to debug
> > assembler.
> 
> I take it the symbols are of use to ocamldebug then?  Or could we just strip
> useless baggage and discard?

In ordinary Fedora C packages, foo-debuginfo contains the unstripped
object files (ie. containing DWARF debugging info).  The base
package ('foo') is stripped of course.  However the programs in
the base package contain a special buildid section, which, with a
suitably modified version of gdb, causes gdb to get the right
symbols out of the corresponding foo-debuginfo file.

All well and good for ordinary C/C++ programs.  However OCaml has
its own native code generator (ie. it generates machine code directly).
This code generator doesn't embed any DWARF debugging info, and as
a result if you try to generate a ocaml-foo-debuginfo subpackage
it will usually be empty.  (Except in some special cases, ie.
where C code is linked in to the program).  Thus we disable
generation of ocaml-foo-debuginfo subpackages as a matter of policy.

There's a separate issue which is that gdb is still able to
find ordinary symbols in unstripped OCaml executables, but because
gdb doesn't have DWARF info and in any case doesn't know anything
about the OCaml language, all it can do is show symbol locations
in assembler.  Believe it or not, I have debugged OCaml programs
on many occasions using gdb like this ...

ocamldebug is quite separate.  Firstly it only works on bytecode-
compiled OCaml programs.  Secondly, OCaml bytecode contains its
own debugging information, not related to and totally incompatible
with DWARF, which is only understood by ocamldebug and a few other
programs like ocamlprof.

Some enterprising person with LOTS of time on their hands needs
to add DWARF output to the OCaml native code generator(s), and
add support for the OCaml language in gdb.

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