Re: [PATCH] Update testsuite mechanism to allow object files as source files.

[Andrew Burgess <andrew.burgess@embecosm.com>]

* Eric Christopher via Gdb-patches <gdb-patches@sourceware.org> [2020-07-16 14:16:46 -0700]:

> Should be just gas in the binutils-gdb checkout?

GDB's DWARF assembler is written in TCL, and generates a .S file
containing the debug sections and their contents.

A test will usually consist of some DWARF written in TCL and a C file.
The C file is compiled without debug information and the TCL code then
places references to symbols in the C file into the generated DWARF.

The DWARF assembler then creates a .S file, which is assembled and
linked with the C file.

We then start up GDB and debug as normal.

Thanks,
Andrew




> 
> -eric
> 
> On Thu, Jul 16, 2020 at 2:10 PM Caroline Tice via Gdb-patches <
> gdb-patches@sourceware.org> wrote:
> 
> > Has the DWARF assembler in the GDB testsuite been updated to handle
> > DWARF v5?  Or can it handle that automatically?  Is there a good
> > example I can look at to see how to use it?
> >
> > -- Caroline
> > cmtice@google.com
> >
> > On Thu, Jul 16, 2020 at 1:12 PM Tom Tromey <tom@tromey.com> wrote:
> > >
> > > Joseph> On general free software and reproducible builds principles:
> > > Joseph> * The source for any checked-in object file should be checked in.
> > > Joseph> * That source should include comments giving all information
> > required to
> > > Joseph> be able to reproduce the object file byte-for-byte
> > >
> > > In the past we tried this kind of thing, by taking the assembly
> > > generated by the compiler, then editing it and checking it in.
> > >
> > > However, IMO, this turned out to be a pain.  The hand editing was often
> > > not sufficiently documented, and the tests were still
> > > architecture-dependent.  Once or twice I think someone has had to edit
> > > the .S file later, which is error-prone.  Also, the earliest test suite
> > > additions like this didn't include the original source, making this
> > > harder to handle.
> > >
> > > The "DWARF assembler" in the test suite avoids all this, at least for
> > > tests that require particular debuginfo.  The main drawbacks of this
> > > approach are (again IMO) that sometimes it's a pain to write the DWARF
> > > by hand, and that sometimes the assembler framework itself needs
> > > upgrades before one can even begin.  However, the tests are much more
> > > robust.
> > >
> > > I'd encourage the extension of the latter approach as much as possible.
> > > It isn't perfect but IME has been better on the whole.
> > >
> > > Tom
> >