Re: RFC Re: [PATCH] Shorter object file names under subdir-objects

[Mathieu Lirzin]

Hello,

Thomas Martitz <address@hidden> writes:

> Am 23.04.2017 um 18:39 schrieb Mathieu Lirzin:
>
>>> From 8cd0a71abac70bbdcaac804dc7964fa9f34753a0 Mon Sep 17 00:00:00 2001
>>> From: Thomas Martitz <address@hidden>
>>> Date: Mon, 13 Mar 2017 12:41:59 +0100
>>> Subject: [PATCH 1/3] Shorter object file names under subdir-objects
>>>
>>> With the %reldir% feature, object file names can become very long, because 
>>> the
>>> file names are prefixed with the %canon_reldir% substitution. The reason is 
>>> to
>>> achieve unique object file names when target-specific CFLAGS or similar are
>>> used. When subdir-objects is also in effect, these long file names are also
>>> placed in potentially deep subdirectories.
>>>
>>> But with subdir-objects this is unnecessary, since uniqueness of the object
>>> file names is already achieved by placing them next to the unique source 
>>> files.
>>>
>>> Therefore, this changes strips paths components, that are caused by
>>> %canon_reldir% or otherwise, from the object file names. The object file 
>>> name
>>> is prefixed by the target in case of target-specific CFLAGS. As a result, 
>>> the
>>> build tree looks less scary and many cases where $var_SHORTNAME was 
>>> necessary
>>> can now be avoided. Remember that the use of $var_SHORTNAME is discouraged 
>>> (and
>>> is not always an option since it does not work inside conditionals).
>>>
>>> There is one exception to the above: if the same source file is linked to
>>> separate programs/libraries with per-executable flags and the
>>> programs/libraries have identical names, then uniqueness of truncated object
>>> file names is broken. Therefore the truncation is prevented for these 
>>> targets
>>> if there happens to be identically named progams or libraries,
>>>
>>> Example:
>>> previously:
>>>   sub/Makefile.am:
>>>   AUTOMAKE_OPTIONS = subdir-objects
>>>   bin_PROGRAMS += %D%/foo
>>>   %C%_foo_CFLAGS = $(AM_CFLAGS) -g
>>>
>>> resulted in objects:
>>>   sub/sub_foo-foo.o
>>>
>>> now object file name is:
>>>   sub/foo-foo.o
>>> ---
>>>  NEWS                        |   6 +++
>>>  bin/automake.in             |  90 ++++++++++++++++++++++++++++++++--
>>>  t/list-of-tests.mk          |   1 +
>>>  t/subdir-objects-objname.sh | 115 
>>> ++++++++++++++++++++++++++++++++++++++++++++
>>>  4 files changed, 207 insertions(+), 5 deletions(-)
>>>  create mode 100644 t/subdir-objects-objname.sh
>>
>> [...]
>>
>>> From 5cf501dd932b4aabcc60b489e4f19c2ad8a757cc Mon Sep 17 00:00:00 2001
>>> From: Mathieu Lirzin <address@hidden>
>>> Date: Thu, 13 Apr 2017 14:19:15 +0200
>>> Subject: [PATCH 2/3] Test that should pass.
>>>
>>> The test ensures that programs with equal names get unique object files even
>>> if object file name truncation is in effect.
>>> ---
>>>  t/list-of-tests.mk        |  1 +
>>>  t/subobj-objname-clash.sh | 58 
>>> +++++++++++++++++++++++++++++++++++++++++++++++
>>>  2 files changed, 59 insertions(+)
>>>  create mode 100644 t/subobj-objname-clash.sh
>>
>> [...]
>>
>>> From 508b7e19745d88dbd1100b403fec440abfd151bb Mon Sep 17 00:00:00 2001
>>> From: Thomas Martitz <address@hidden>
>>> Date: Sat, 22 Apr 2017 00:51:44 +0200
>>> Subject: [PATCH 3/3] Extend subobj-objname-clash.sh test with such that it
>>>  also looks for clashes in libraries.
>>>
>>> ---
>>>  t/subobj-objname-clash.sh | 32 +++++++++++++++++++++++++++++---
>>>  1 file changed, 29 insertions(+), 3 deletions(-)
>>
>> At first glance, I think it would be reasonable to reduce the 3 tests to
>> only 1 which checks that there is no name clash between multiple
>> _PROGRAMS and _LIBRARIES.
>>
>> Can you send an updated patch which includes both your code and the
>> suggested test?
>
>
> Sorry, I don't get which 3 tests you refer to, please
> explain. 

There is one test in each patch you sent (including the patch I sent).

> Currently there are two test scripts included: one checks for
> the object file names to see if they are truncated (or not). 

Since Automake doesn't provide any garantee about object file names.  I
don't think we need to include such test in the test suite.

> The other one checks in an abstract way if the wrong object file was
> included in a binary (due to potential name clashes with my change).
>
> Also, do you suggest that I shall squash the 3 patch files into one? I
> didn't do so as to not lose the authorship information on your test
> script.

Yes, that was my suggestion.  In this particular case, I don't care
about my authorship information.  You deserve all the credits.  :)

Thanks.

-- 
Mathieu Lirzin
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