Make's "define" feature (macros) is subtle and it took me a long time to
convince myself this all works. In particular, we (prior to this commit)
are terribly inconsistent about the use of `$` vs `$$`. We mostly get
away with it because the "variables" are more like "constants", but the
inconsistency trips up some things. For example, using `$(shell)`
inside a macro will run at macro expansion time rather than when the
resulting make code is executed.
For a contrived, but concrete example, derived from our Makefile:
```
define MACRO
ifeq ($(DBG),1)
$(warning dbg is $(DBG))
endif
endef # macro
TGTS=a b c
$(foreach pfx, $(TGTS), $(eval $(MACRO)))
default:
@echo $@
```
yields:
```
$ make
Makefile:8: dbg is
Makefile:8: dbg is
Makefile:8: dbg is
default
$ make DBG=1
Makefile:8: dbg is 1
Makefile:8: dbg is 1
Makefile:8: dbg is 1
default
```
This is because `$(warning)` is evaluated as the macro is expanded.
Replace that with `$(shell)` and you can see how you might end up
running a bunch of things you didn't need to run. The fix is:
```
define MACRO
ifeq ($(DBG),1)
$$(warning dbg is $$(DBG))
endif
endef # macro
TGTS=a b c
$(foreach pfx, $(TGTS), $(eval $(MACRO)))
default:
@echo $@
```
which yields:
```
$ make
default
$ make DBG=1
Makefile:8: dbg is 1
Makefile:8: dbg is 1
Makefile:8: dbg is 1
default
```
We COULD have only changed `$(warning)` to `$$(warning)` and left
`$(DBG)` alone, because that's a cheap expansion. I chose NOT to do
that here because it requires brainpower to think about this all, and it
seems easier to set a simple rule: inside a `define`/`endef` block, you
always use `$$` unless you KNOW that you NEED expansion-time evaluation
(as in the `$(prefix)` in this commit, which is effectively an argument
to the macros).
Only build and run go2make on the first pass. If that generates a new
GO_PKGDEPS_FILE, make will restart the whole process and set MAKE_RESTARTS to
a numeric value.
We can use this to avoid re-running go2make, which saves a few seconds
each build.
The alternative to this would be to special-case code-generator. Since
it legit wants codegen, it seems wrong to make it be _examples (which tools
should ignore).
Make examples an "internal module" so the main go.mod for
k8s.io/code-generator does not get too polluted.
Because this comment is in a `define` which is later evaluated, the
syntactical `$(eval)` is treated like a variable exapansion. Just
change the comment.
Driving towards `make --warn-undefined-variables`.
As per #96015 and other reports, conversion-gen does the wrong thing if
dependent packages are not ALSO being re-generated. It creates new
versions of generated files that have missing conversions.
This change passes all packages as "extras" which will be parsed but not
regenerated (default already does exactly this).
This allows the execution of the Makefiles from distributions which do
have `bash` in a different path.
Signed-off-by: Sascha Grunert <sgrunert@suse.com>
Use GNU Make 4.2.1(such as fedora-29) to build k8s in a long directory,
it failed with `execvp: /bin/bash: Argument list too long'
[snip]
$ cd /buildarea1/hjia/wrlinux-1019/I_/suspect_/that_/if_/you_/create_/your_/project_/in_/a_/very_/deep_/directory/build_master-wr_qemux86-64_faw_2019090509/build/tmp-glibc/work/core2-64-wrs-linux/kubernetes/v1.16.0-alpha+git7054e3ead7e1a00ca6ac3ec47ea355b76061a35a-r0/kubernetes-v1.16.0-alpha+git7054e3ead7e1a00ca6ac3ec47ea355b76061a35a/src/import
$ make cross KUBE_BUILD_PLATFORMS=linux/amd64 GOLDFLAGS=""
|+++ [0804 16:38:32] Building go targets for linux/amd64:
| ./vendor/k8s.io/code-generator/cmd/deepcopy-gen
|make[1]: execvp: /bin/bash: Argument list too long
|make[1]: *** [Makefile.generated_files:184: pkg/kubectl/cmd/testing/zz_generated.deepcopy.go] Error 127
|make: *** [Makefile:557: generated_files] Error 2
...
[snip]
From make manual [1]
$?
The names of all the prerequisites that are newer than the target, with spaces between them.
While two `$?' was passed to bash in a line, it caused above failure,
drop a duplicated one could workaround the issue.
[1] https://www.gnu.org/software/make/manual/html_node/Automatic-Variables.html
Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Added explanation of the `k8s:conversion-gen-external-types` comment
tag.
Added explanation of how the developer can selectively override the
generated conversion functions.
Also updated description in Makefile.generated_files.
One can run:
make generated_files UPDATE_API_KNOWN_VIOLATIONS=true
to update the checked-in known API violation exceptions list.
Also updated README and the error message on how to resolve the
failure.
Automatic merge from submit-queue (batch tested with PRs 66341, 66405, 66403, 66264, 66447). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Move api rules list under api-approvers-owned package
Additions to this list should be rare and carefully reviewed
```release-note
NONE
```
check in existing API rule violations;
the Make rule fails if generated violation report differs from the
checked-in violation file and prints error message;
add documentation.
