llvm dev - Jun 2019 - [RFC] [tools] Changing Behavior of LLVM binutils When No File Is Specified

Sounds good, I'll work on removing these in favor of defaulting to stdin
then?
> I think it would be much friendlier to just print "file or pipe
expected"
and then print the help.
Do you have thoughts on this? I'm not sure there is a clean way to do this,
the cleanest would be through getFileOrSTDIN(), but I'm not sure all of its
users want this behavior. I don't think we need it personally, but if you
think its a good quality of life change to the tools and worth working on,
I'd be happy to do so.

On Wed, Jun 26, 2019 at 1:41 AM Fāng-ruì Sòng <maskray at google.com>
wrote:
> GNU addr2line, nm, objdump, and size default to a.out when no input file
> is specified.
> Among llvm binary utilities, llvm-nm llvm-objdump llvm-size llvm-dwarfdump
> default to a.out.
>
> I agree with Michael that a.out behavior may not be used by many people.
> If people don't care too much
> about these utilities' compatibility with GNU, deleting the default
a.out
> LGTM.
>
> (I am opposed to make more utilities default to a.out)
>
> On Wed, Jun 26, 2019 at 9:02 AM Alex Brachet-Mialot via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> > Does anyone actually use the default to a.out behavior?
>> This is a good point. What bugs me is continuity across the tools, I
>> agree with you that it isn't particularly useful to default to
a.out. But
>> we are kind of stuck with the weird way that GNU's binutils do
things. I am
>> not in favor of llvm-objdump defaulting to a.out, but llvm-readelf
giving
>> this warning message. My guess is that moving away from using a.out by
>> default for llvm-objdump, llvm-nm and others whose gnu counter parts do
>> this would be more disruptive than my proposal.
>>
>> As Jake pointed out we use "-" to describe stdin/stdout,
GNU's tools do
>> not do this, so I think there is some precedence for us slightly
modifying
>> behavior when we can reasonably say things will not happen, like the
file
>> "-" existing.
>>
>> On Tue, Jun 25, 2019 at 8:28 PM Michael Spencer <bigcheesegs at
gmail.com>
>> wrote:
>>
>>> On Tue, Jun 25, 2019 at 4:58 PM Alex Brachet-Mialot via llvm-dev
<
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> Some binutils, nm comes to mind, when to input file is
specified will
>>>> default to a.out. Others do not do this and read from stdin by
default. The
>>>> rest of this email will be specifically referencing these which
read from
>>>> stdin, and not the tools which for various reasons do things
differently.
>>>>
>>>> I propose that we change the behavior of these tools to use
a.out when
>>>> appropriate. By appropriate I mean firstly, no input file
specified and
>>>> also no stream redirection to stdin. These are the file types
of stdin in
>>>> these scenarios:
>>>> $ writes-to-stdout | prog # named pipe (fifo)
>>>> $ prog < file # regular file
>>>> $ prog # reading from tty, character device
>>>>
>>>> Perhaps if stdin is a named pipe or regular file, then the
default
>>>> behavior should be as it always was, to read from stdin, but if
stdin is a
>>>> tty then we should use a.out as a default file. This lets these
tools act
>>>> the same as their gnu counterparts (when meaningful) but also
adds what I
>>>> think is convenient to not have to specify a.out.
>>>>
>>>> This proposal would look something like this:
>>>> $ llvm-strings # not meanigful to read from stdin here, look
for a.out
>>>> $ llvm-strings < file # use stdin
>>>>
>>>> I may have got the behavior of stream redirection wrong here,
or missed
>>>> a situation when reading from the terminal is useful. I would
love some
>>>> feedback.
>>>>
>>>> Best,
>>>> Alex
>>>>
>>>>
>>> Does anyone actually use the default to a.out behavior?  I think it
>>> would be much friendlier to just print "file or pipe
expected" and then
>>> print the help.
>>>
>>> - Michael Spencer
>>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
>
> --
> 宋方睿
>
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I agree with others that the a.out behaviour is weird (I've even thought
this about the linker output being called a.out since I started
programming, but perhaps that's a different story). The use-case I can
imagine is something like:

$ ld.lld test.o
$ llvm-objdump -d

I.e. using a tool immediately after generating the linker output. However,
I don't think this is likely actually done by anybody, and I think it's
probably safe to change the behaviour here. I'd rather be universal across
the tools (e.g. always read from stdin) than do this frankly. An error
message about a missing input file might be nice in some cases
(llvm-readelf, llvm-objdump, llvm-nm), but I think we definitely want to
support the option of stdin redirection if nothing else but for test
purposes. If it's complicated to achieve both the error under
non-redirection cases, and no error in redirection cases then I'd prefer
the latter.

Regards,

James

On Wed, 26 Jun 2019 at 08:28, Alex Brachet-Mialot via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Sounds good, I'll work on removing these in favor of defaulting to
stdin
> then?
>
> > I think it would be much friendlier to just print "file or pipe
> expected" and then print the help.
> Do you have thoughts on this? I'm not sure there is a clean way to do
> this, the cleanest would be through getFileOrSTDIN(), but I'm not sure
all
> of its users want this behavior. I don't think we need it personally,
but
> if you think its a good quality of life change to the tools and worth
> working on, I'd be happy to do so.
>
> On Wed, Jun 26, 2019 at 1:41 AM Fāng-ruì Sòng <maskray at google.com>
wrote:
>
>> GNU addr2line, nm, objdump, and size default to a.out when no input
file
>> is specified.
>> Among llvm binary utilities, llvm-nm llvm-objdump llvm-size
>> llvm-dwarfdump default to a.out.
>>
>> I agree with Michael that a.out behavior may not be used by many
people.
>> If people don't care too much
>> about these utilities' compatibility with GNU, deleting the default
a.out
>> LGTM.
>>
>> (I am opposed to make more utilities default to a.out)
>>
>> On Wed, Jun 26, 2019 at 9:02 AM Alex Brachet-Mialot via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> > Does anyone actually use the default to a.out behavior?
>>> This is a good point. What bugs me is continuity across the tools,
I
>>> agree with you that it isn't particularly useful to default to
a.out. But
>>> we are kind of stuck with the weird way that GNU's binutils do
things. I am
>>> not in favor of llvm-objdump defaulting to a.out, but llvm-readelf
giving
>>> this warning message. My guess is that moving away from using a.out
by
>>> default for llvm-objdump, llvm-nm and others whose gnu counter
parts do
>>> this would be more disruptive than my proposal.
>>>
>>> As Jake pointed out we use "-" to describe stdin/stdout,
GNU's tools do
>>> not do this, so I think there is some precedence for us slightly
modifying
>>> behavior when we can reasonably say things will not happen, like
the file
>>> "-" existing.
>>>
>>> On Tue, Jun 25, 2019 at 8:28 PM Michael Spencer <bigcheesegs at
gmail.com>
>>> wrote:
>>>
>>>> On Tue, Jun 25, 2019 at 4:58 PM Alex Brachet-Mialot via
llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>
>>>>> Some binutils, nm comes to mind, when to input file is
specified will
>>>>> default to a.out. Others do not do this and read from stdin
by default. The
>>>>> rest of this email will be specifically referencing these
which read from
>>>>> stdin, and not the tools which for various reasons do
things differently.
>>>>>
>>>>> I propose that we change the behavior of these tools to use
a.out when
>>>>> appropriate. By appropriate I mean firstly, no input file
specified and
>>>>> also no stream redirection to stdin. These are the file
types of stdin in
>>>>> these scenarios:
>>>>> $ writes-to-stdout | prog # named pipe (fifo)
>>>>> $ prog < file # regular file
>>>>> $ prog # reading from tty, character device
>>>>>
>>>>> Perhaps if stdin is a named pipe or regular file, then the
default
>>>>> behavior should be as it always was, to read from stdin,
but if stdin is a
>>>>> tty then we should use a.out as a default file. This lets
these tools act
>>>>> the same as their gnu counterparts (when meaningful) but
also adds what I
>>>>> think is convenient to not have to specify a.out.
>>>>>
>>>>> This proposal would look something like this:
>>>>> $ llvm-strings # not meanigful to read from stdin here,
look for a.out
>>>>> $ llvm-strings < file # use stdin
>>>>>
>>>>> I may have got the behavior of stream redirection wrong
here, or
>>>>> missed a situation when reading from the terminal is
useful. I would love
>>>>> some feedback.
>>>>>
>>>>> Best,
>>>>> Alex
>>>>>
>>>>>
>>>> Does anyone actually use the default to a.out behavior?  I
think it
>>>> would be much friendlier to just print "file or pipe
expected" and then
>>>> print the help.
>>>>
>>>> - Michael Spencer
>>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>
>>
>> --
>> 宋方睿
>>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Like James, Michael suggested, I would prefer the default behavior be consistent
across tools (either always read from stdin or no default at all /give error
messages)

From: James Henderson <jh7370.2008 at my.bristol.ac.uk>
Sent: Wednesday, June 26, 2019 2:31 AM
To: Alex Brachet-Mialot <alexbrachetmialot at gmail.com>
Cc: Fāng-ruì Sòng <maskray at google.com>; LLVMDev <llvm-dev at
lists.llvm.org>; Jordan Rupprecht <rupprecht at google.com>; Chen,
Yuanfang <Yuanfang.Chen at sony.com>
Subject: Re: [llvm-dev] [RFC] [tools] Changing Behavior of LLVM binutils When No
File Is Specified

I agree with others that the a.out behaviour is weird (I've even thought
this about the linker output being called a.out since I started programming, but
perhaps that's a different story). The use-case I can imagine is something
like:

$ ld.lld test.o
$ llvm-objdump -d

I.e. using a tool immediately after generating the linker output. However, I
don't think this is likely actually done by anybody, and I think it's
probably safe to change the behaviour here. I'd rather be universal across
the tools (e.g. always read from stdin) than do this frankly. An error message
about a missing input file might be nice in some cases (llvm-readelf,
llvm-objdump, llvm-nm), but I think we definitely want to support the option of
stdin redirection if nothing else but for test purposes. If it's complicated
to achieve both the error under non-redirection cases, and no error in
redirection cases then I'd prefer the latter.

Regards,

James

On Wed, 26 Jun 2019 at 08:28, Alex Brachet-Mialot via llvm-dev <llvm-dev at
lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
Sounds good, I'll work on removing these in favor of defaulting to stdin
then?
> I think it would be much friendlier to just print "file or pipe
expected" and then print the help.
Do you have thoughts on this? I'm not sure there is a clean way to do this,
the cleanest would be through getFileOrSTDIN(), but I'm not sure all of its
users want this behavior. I don't think we need it personally, but if you
think its a good quality of life change to the tools and worth working on,
I'd be happy to do so.

On Wed, Jun 26, 2019 at 1:41 AM Fāng-ruì Sòng <maskray at
google.com<mailto:maskray at google.com>> wrote:
GNU addr2line, nm, objdump, and size default to a.out when no input file is
specified.
Among llvm binary utilities, llvm-nm llvm-objdump llvm-size llvm-dwarfdump
default to a.out.

I agree with Michael that a.out behavior may not be used by many people. If
people don't care too much
about these utilities' compatibility with GNU, deleting the default a.out
LGTM.

(I am opposed to make more utilities default to a.out)

On Wed, Jun 26, 2019 at 9:02 AM Alex Brachet-Mialot via llvm-dev <llvm-dev at
lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>
wrote:
> Does anyone actually use the default to a.out behavior?
This is a good point. What bugs me is continuity across the tools, I agree with
you that it isn't particularly useful to default to a.out. But we are kind
of stuck with the weird way that GNU's binutils do things. I am not in favor
of llvm-objdump defaulting to a.out, but llvm-readelf giving this warning
message. My guess is that moving away from using a.out by default for
llvm-objdump, llvm-nm and others whose gnu counter parts do this would be more
disruptive than my proposal.

As Jake pointed out we use "-" to describe stdin/stdout, GNU's
tools do not do this, so I think there is some precedence for us slightly
modifying behavior when we can reasonably say things will not happen, like the
file "-" existing.

On Tue, Jun 25, 2019 at 8:28 PM Michael Spencer <bigcheesegs at
gmail.com<mailto:bigcheesegs at gmail.com>> wrote:
On Tue, Jun 25, 2019 at 4:58 PM Alex Brachet-Mialot via llvm-dev <llvm-dev at
lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
Some binutils, nm comes to mind, when to input file is specified will default to
a.out. Others do not do this and read from stdin by default. The rest of this
email will be specifically referencing these which read from stdin, and not the
tools which for various reasons do things differently.

I propose that we change the behavior of these tools to use a.out when
appropriate. By appropriate I mean firstly, no input file specified and also no
stream redirection to stdin. These are the file types of stdin in these
scenarios:
$ writes-to-stdout | prog # named pipe (fifo)
$ prog < file # regular file
$ prog # reading from tty, character device

Perhaps if stdin is a named pipe or regular file, then the default behavior
should be as it always was, to read from stdin, but if stdin is a tty then we
should use a.out as a default file. This lets these tools act the same as their
gnu counterparts (when meaningful) but also adds what I think is convenient to
not have to specify a.out.

This proposal would look something like this:
$ llvm-strings # not meanigful to read from stdin here, look for a.out
$ llvm-strings < file # use stdin

I may have got the behavior of stream redirection wrong here, or missed a
situation when reading from the terminal is useful. I would love some feedback.

Best,
Alex


Does anyone actually use the default to a.out behavior?  I think it would be
much friendlier to just print "file or pipe expected" and then print
the help.

- Michael Spencer
_______________________________________________
LLVM Developers mailing list
llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev


--
宋方睿
_______________________________________________
LLVM Developers mailing list
llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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