[bug #54675] avoid redundant recipe warning for identical recipes

[David Boyce]

URL:
<https://savannah.gnu.org/bugs/?54675>

Summary: avoid redundant recipe warning for identical recipes
Project: make
Submitted by: boyski
Submitted on: Tue 18 Sep 2018 01:23:09 AM UTC
Severity: 3 - Normal
Item Group: Enhancement
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
Component Version: SCM
Operating System: None
Fixed Release: None
Triage Status: None

_______________________________________________________

Details:

I'm wondering whether it might be reasonable to skip the redundant-recipe
warnings if the recipes are identical anyway. Test case:

% cat makefile
.PHONY: all
all:
foo:; touch $@
foo:; touch $@

% make
makefile:5: warning: overriding recipe for target 'foo'
makefile:4: warning: ignoring old recipe for target 'foo'
make: Nothing to be done for 'all'.

It looks like this might be avoidable with a strcmp in read.c around line 2113
(in current SCM) though I'm not in a position to try it now.

This comes up because I have various macros and helper makefiles which
generate rules to create directory paths. The recipe to create a directory
will in all cases be "mkdir $@" in my use case but when multiple macros end up
generating identical rules these spurious warnings are still printed. Of
course it can be programmed around but I wonder whether it's worth giving the
warning at all here.






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[Brian Vandenberg]

On the one hand that might seem convenient, but that would open the
door to mistakes being introduced that you would undoubtedly want to
avoid, eg:

* accidental copy/paste
* someone else adding conflicting recipes (disabling the warning would
make this unnoticeable)

I handled 'mkdir' stuff by adding mkdir to all the recipes. It's not
ideal but it works.

-brian

Post by David Boyce
<https://savannah.gnu.org/bugs/?54675>
Summary: avoid redundant recipe warning for identical recipes
Project: make
Submitted by: boyski
Submitted on: Tue 18 Sep 2018 01:23:09 AM UTC
Severity: 3 - Normal
Item Group: Enhancement
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
Component Version: SCM
Operating System: None
Fixed Release: None
Triage Status: None
_______________________________________________________
I'm wondering whether it might be reasonable to skip the redundant-recipe
% cat makefile
.PHONY: all
% make
makefile:5: warning: overriding recipe for target 'foo'
makefile:4: warning: ignoring old recipe for target 'foo'
make: Nothing to be done for 'all'.
It looks like this might be avoidable with a strcmp in read.c around line 2113
(in current SCM) though I'm not in a position to try it now.
This comes up because I have various macros and helper makefiles which
generate rules to create directory paths. The recipe to create a directory
generating identical rules these spurious warnings are still printed. Of
course it can be programmed around but I wonder whether it's worth giving the
warning at all here.
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<https://savannah.gnu.org/bugs/?54675>
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[David Boyce]

someone else adding conflicting recipes (disabling the warning would make

this unnoticeable)

But they wouldn't be *conflicting* recipes. The whole point of this
discussion is to remove warnings for *identical* recipes. The enhancement
request is indeed arguable, but it's not about conflicting recipes.

accidental copy/paste

Yes, a case can be made that people might want to be alerted to the fact
that they have redundant recipes as a result of accidental copy/paste or
similar. This is a reasonable subject for debate/discussion.

I handled 'mkdir' stuff by adding mkdir to all the recipes. It's not

ideal but it works.

Well, no, it isn't and it doesn't. We're getting well away from the initial
subject but I'll give the background anyway:

Depending on platform, mkdir in recipes is somewhere between broken and
inelegant. I've written this up in detail for my employer but the short
version is that mkdir is a particularly complex case in parallel builds due
to race conditions when creating shared parent directories. In the end
there's only one threadsafe, portable, and clean way of making directories
and that's to hand the job to make via an order-only dependency:

$(list-of-required-directories):
mkdir $@

target: | <parent-directory>

Directory creation in recipes is subject to random failure in -j scenarios
but you can get away with it on GNU platforms such as Linux because GNU
mkdir has a builtin retry mechanism. Thus, on GNU platforms it's merely
inelegant while on non-GNU platforms it's unsafe.

It's worth noting that the above can be made simpler by use of
.SECONDEXPANSION:

target: | $$(@D)

David

On the one hand that might seem convenient, but that would open the
door to mistakes being introduced that you would undoubtedly want to
* accidental copy/paste
* someone else adding conflicting recipes (disabling the warning would
make this unnoticeable)
I handled 'mkdir' stuff by adding mkdir to all the recipes. It's not
ideal but it works.
-brian

Post by David Boyce
<https://savannah.gnu.org/bugs/?54675>
Summary: avoid redundant recipe warning for identical

recipes

Post by David Boyce
Project: make
Submitted by: boyski
Submitted on: Tue 18 Sep 2018 01:23:09 AM UTC
Severity: 3 - Normal
Item Group: Enhancement
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
Component Version: SCM
Operating System: None
Fixed Release: None
Triage Status: None
_______________________________________________________
I'm wondering whether it might be reasonable to skip the redundant-recipe
% cat makefile
.PHONY: all
% make
makefile:5: warning: overriding recipe for target 'foo'
makefile:4: warning: ignoring old recipe for target 'foo'
make: Nothing to be done for 'all'.
It looks like this might be avoidable with a strcmp in read.c around

line 2113

Post by David Boyce
(in current SCM) though I'm not in a position to try it now.
This comes up because I have various macros and helper makefiles which
generate rules to create directory paths. The recipe to create a

directory
end up

Post by David Boyce
generating identical rules these spurious warnings are still printed. Of
course it can be programmed around but I wonder whether it's worth

giving the

Post by David Boyce
warning at all here.
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