On 08/23/2017 11:24 PM, Mathieu Lirzin wrote:
> Michael Haubenwallner <michael.haubenwall...@ssi-schaefer.com> writes:
>> On 08/22/2017 12:40 AM, Mathieu Lirzin wrote:
>>> Michael Haubenwallner <michael.haubenwall...@ssi-schaefer.com> writes:
>>>
>>>> In this case let me come up with attached patch for now
>>>> (without deeper knowledge of automake internals though).
>>>
>>> I have tested this patch, and confirm that it fixes the bug. However I
>>> have on question regarding the added code.
>>>
>>>> From c3d51adb53400fc8bf65c0e003d810b2e7166d0d Mon Sep 17 00:00:00 2001
>>>> From: Michael Haubenwallner <michael.haubenwall...@ssi-schaefer.com>
>>>> Date: Wed, 16 Aug 2017 18:16:12 +0200
>>>> Subject: [PATCH] automake: Depend on LIBOBJDIR for LIBOBJS.
>>>>
>>>> This change fixes automake bug#27781.
>>>>
>>>> * bin/automake.in: Add Makefile dependency on LIBOBJDIR/dirstamp for
>>>> each LIBOBJS/ALLOCA variable used.
>>>> ---
>>>> bin/automake.in | 11 ++++++++++-
>>>> 1 file changed, 10 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/bin/automake.in b/bin/automake.in
>>>> index 9c4cb86..b82e8c5 100644
>>>> --- a/bin/automake.in
>>>> +++ b/bin/automake.in
>>>> @@ -2153,10 +2153,19 @@ sub handle_LIBOBJS_or_ALLOCA
>>>> $dir = backname ($relative_dir) . "/$dir"
>>>> if $relative_dir ne '.';
>>>> define_variable ('LIBOBJDIR', "$dir", INTERNAL);
>>>> + my $dirstamp = '';
>>>> + # Abusing $clean_files{"$(VAR)"} as indicator for whether
>>>> + # we have added the "$(VAR): $dirstamp" dependency already.
>>>
>>> I am not sure to understand what this comment really means. Can you
>>> explain it in other words?
>>>
>>>> + $dirstamp = require_build_directory ($dir)
>>
>> Thing is, $dirstamp is calculated only when ...
>>
>>>> + if ! defined $clean_files{"\$($var)"};
>>
>> ... $clean_files{} was defined, which is done ...
>>
>>>> $clean_files{"\$($var)"} = MOSTLY_CLEAN;
>>
>> ... here. Subsequently, $output_rules is extended only when $dirstamp was
>> calculated:
>>
>>>> + $output_rules .= "\$($var): $dirstamp\n" if ($dirstamp);
>>
>> But the name "clean_files" feels somewhat unrelated to the dirstamp
>> dependency
>> (as in causing a different output by itself), because I use it to make sure
>> the dirstamp rule is added only once to $output_rules:
>> Within flex, I've seen handle_LIBOBJS_or_ALLOCA to be called thrice, but this
>> dirstamp rule is enough once, as "\$($var)" holds all three object files.
>> While I have also thought about adding this dependency for each explicit
>> object file separately - which would not need the "clean_files" indicator,
>> I've failed to identify where to get the correct object file name from.
>
> OK so this is mostly an optimization, since having multiple time the
> same line shouldn't hurt.
Agreed.
> Let's first fix the without such optimization.
I'm going to look into the (other subthread's) AC_LIBOBJ thing,
for adding the rule per explicit object file instead.
>>
>>>> # If LTLIBOBJS is used, we must also clear LIBOBJS (which might
>>>> # be created by libtool as a side-effect of creating LTLIBOBJS).
>>>> - $clean_files{"\$($var)"} = MOSTLY_CLEAN if $var =~ s/^LT//;
>>>> + if ($var =~ s/^LT//) {
>>>> + $clean_files{"\$($var)"} = MOSTLY_CLEAN;
>>>> + $output_rules .= "\$($var): $dirstamp\n" if ($dirstamp);
>>>> + }
>>>> }
>>>>
>>>> return $dir;
>>
>
> Regarding that part of the code even before you made it seems to me that
> the conditional second '$clean_files{"\$($var)"} = MOSTLY_CLEAN'
> statement is useless. Am I overlooking something?
It took a while for me too to understand what's going on here:
Consider $var = 'LTLIBOBJS';
> Here is the snippet of the code before your changed.
>
> --8<---------------cut here---------------start------------->8---
> define_variable ('LIBOBJDIR', "$dir", INTERNAL);
> $clean_files{"\$($var)"} = MOSTLY_CLEAN;
here, unconditionally: $clean_files{'$(LTLIBOBJS)'} = MOSTLY_CLEAN;
> # If LTLIBOBJS is used, we must also clear LIBOBJS (which might
> # be created by libtool as a side-effect of creating LTLIBOBJS).
> $clean_files{"\$($var)"} = MOSTLY_CLEAN if $var =~ s/^LT//;
Crucial here is that trailing { if $var =~ s/^LT// }:
First, leading 'LT' eventually is dropped: $var = 'LIBOBJS';
If the leading 'LT' was actually found: $clean_files{'LIBOBJS'} = MOSTLY_CLEAN;
> --8<---------------cut here---------------end--------------->8---
>
>> Another thought about the final "$(LIBOBJS): .../.dirstamp" Makefile line:
>> If I remember correctly, there have been (non-GNU) make implementations that
>> choke on this rule when LIBOBJS is an empty variable:
>> Am I wrong here, or is GNU make required anyway these days?
>
> GNU make is not required for current Automake version. I didn't find
> any reference of this issue with empty variable target in Autoconf
> "Portable Make programming" section [1] but if it is actually the case
> then it would be nice to find a solution for that.
>
/haubi/
