Re: RTe: Location Specs (Was: [pushed v5] gdb/manual: Introduce location specs)

Eli Zaretskii via Gdb-patches
2022-06-02T11:49:28Z

> Date: Thu, 2 Jun 2022 12:10:54 +0100
> Cc: gdb-patches@sourceware.org
> From: Pedro Alves <pedro@palves.net>
>
> > A concrete code location in your program is uniquely identifiable by a
> > set of several attributes: its source line number, the name of its
> > source file, the fully-qualified and prototyped function in which it
> > is defined, and an instruction address. Because each inferior has its
> > own address space, the inferior number is also a necessary part of
> > these attributes. By contrast, location specs you type will many
>
> I built the manual here with the patch, to read in the html form in the browser,
> and found this paragraph very long and dense. I find it much more readable if we have a
> paragraph break here (line break + empty line), before "By contract". Above we talk
> about actual code locations. And below we talk about location specs.

Sure, breaking there is fine, thanks.

> > Several @value{GDBN} commands accept arguments that specify a location
> > or locations of your program's code. Since @value{GDBN} is a
> > source-level debugger, a location specification usually indicates some
> > -line in the source code, but it can also indicate a function name, an
> > -address, a label, and more.
> > +line in some source file, but it can also do that indirectly, by
> > +specifying a function name, an address, a label, etc.
>
> This is changing the meaning of what was said. It is now reading as if
> the line number is what are are after, and that function, address, etc.
> are merely means to get to the line number. While before, we were saying that
> usually you specify the line number, but you can also specify some
> function, or even a precise address. The new text gives a lot more emphasis to
> the resolved line number.

I didn't say "number", though, I just said "line". That's different:
since GDB is a source-level debugger (as the text says), the location
spec identifies some line in the source code. But it doesn't
necessarily do that via its number.

The point of that paragraph, as I interpret it, is to say that a
function name, a label, or an address all identify a certain line in
the source.

> I think it's a difference in the interpretation of "indicate". The original
> text uses it to mean the arguments the user can specify (otherwise it wouldn't
> be talking about "a label" or function _name_), while in your version you seem
> to be using "indicate" to mean the line number you want the spec to resolve to.
>
> There are commands that accept location specs and want to resolve them to
> addresses, others to lines, etc., and you can specify a line to find the address,
> and conversely you can also specify an address to find a line.
>
> Maybe we should say _that_ somehow, instead of the "Since @value{GDBN} is a
> source-level debugger, a location specification usually indicates some
> line" sentence, which I find kind of an unnecessary assertion. Specifying
> function names to break at the function's entry is very usual too, for example.

I'm not sure I understand the issue. "Indicates" was in your original
wording:

Several @value{GDBN} commands accept arguments that specify a location
or locations of your program's code. Since @value{GDBN} is a
source-level debugger, a location specification usually indicates some
line in the source code, but it can also indicate a function name, an
address, a label, and more.

The changes I made to these two sentences are really exceedingly
minor, so I wonder how could they change the meaning. Could you point
to the modifications which change the meaning?

If you meant what the user specifies, then I agree that perhaps
"indicate" is not the best word, but I didn't interpret the above as
alluding to what the user specifies, I interpreted it to what the user
_means_ by the spec: the user always means some source-code level
location.

> > @item
> > For a C@t{++} constructor, the @value{NGCC} compiler generates several
> > -instances of the function body, used in different cases.
> > +instances of the function body, used in different cases, but their
> > +source-level names are identical, unless you qualify them.
>
> What do you mean by "qualify" here?

The "fully-qualified and prototyped function" part.

> Otherwise this looks great!

Thanks.