RE: [PATCH 1/2 ver 2] Fix reverse stepping multiple contiguous PC ranges over the line table.

[Carl Love <cel@us.ibm.com>]

Guinevere:

On Tue, 2023-08-08 at 12:04 +0200, Guinevere Larsen wrote:
> > 

<snip>

> On 07/08/2023 21:03, Carl Love wrote:
> > 
> > diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
> > index 36bf738c667..bffbbf38b09 100644
> > --- a/gdb/testsuite/lib/gdb.exp
> > +++ b/gdb/testsuite/lib/gdb.exp
> > @@ -4896,6 +4896,8 @@ proc quote_for_host { args } {
> >   #     debug information
> >   #   - text_segment=addr: Tell the linker to place the text
> > segment at ADDR.
> >   #   - build-id: Ensure the final binary includes a build-id.
> > +#   - no-column-info: Disable generation of column table
> > information.
> > +#   - column-info: Enable generation of column table information.
> >   #
> >   # And here are some of the not too obscure options understood by
> > DejaGnu that
> >   # influence the compilation:
> > @@ -5105,6 +5107,38 @@ proc gdb_compile {source dest type options}
> > {
> >               } else {
> >                   error "Don't know how to handle text_segment
> > option."
> >               }
> > +	} elseif { $opt == "column-info" } {
> > +	    # If GCC or clang does not support column-info, compilation
> > +	    # will fail and the usupported column-info option will be
> > +	    # reported as such.
> > +	    if {[test_compiler_info {gcc-*}]} {
> 
> I think you missed a bit on an old comment from simon. Way back in
> may, 
> in this email 
> https://sourceware.org/pipermail/gdb-patches/2023-May/199523.html ,
> he 
> mentioned:
> 
> For instance, if you used no-column-info with gcc 6
> (which doesn't support column info at all), gdb_compile should
> succeed,
> even if there isn't an option to disable column info with that
> compiler.
> If you used column-info with gcc 6, gdb_compile would fail.
> 
> So I think this bit should throw an error if it detects gcc-[1-6].

It has been awhile, but as I recall, we decided that the we would
specify column-info and if the compiler doesn't support it then the
compiler will complain (i.e. fail) and we will let the failure be
handled by the normal compiler failure path.  I think that will work
fine?  If there is some concern that is not sufficient, I would be
happy to put in the test   if {[test_compiler_info {gcc-[1-6]-*}]}  for
the $opt == "column-info"  to have the script flag the error. 
Thoughts?

In the case where the compiler doesn't handle the no-column-info flag,
i.e. gcc 1-6, we handle that case by not adding the flag so the
compiler will not flag the error and fail.  In that case, it isn't
going to generate the column info anyways so we don't need to specify
no-column info.


> 
> > +		lappend new_options "additional_flags=-gcolumn-info"
> > +
> > +	    } elseif {[test_compiler_info {clang-*}]} {
> 
> I did some digging, and column-info were added in llvm back in
> october 
> 2012 (commit a2f7eb7c52cdc), which seems to mean support was added
> in 
> llvm 3.2, but I don't see any mention in the release notes. In my 
> opinion, this is old enough that we don't need to have a special
> case, 
> but I wanted to mention, in case some maintainer thinks it should be 
> dealt with.
> 
> If we should, before then, it seems that clang WOULD add column info
> by 
> default, so it should compile with a warning here, and fail if the
> user 
> requested no column info
> 

                                             Carl