On Tue, Jun 16, 2020 at 09:34:30AM +0900, AKASHI Takahiro wrote:
On Mon, Jun 15, 2020 at 10:34:56AM -0400, Tom Rini wrote:
On Sun, Jun 14, 2020 at 09:58:48PM -0600, Simon Glass wrote:
Hi Akashi,
On Sun, 14 Jun 2020 at 20:59, AKASHI Takahiro takahiro.akashi@linaro.org wrote:
On Thu, Jun 04, 2020 at 07:39:35PM -0400, Tom Rini wrote:
On Fri, May 22, 2020 at 04:32:40PM -0600, Simon Glass wrote:
There is a lot of use of #ifdefs in U-Boot. In an effort reduce this, suggest using the compile-time construct.
Signed-off-by: Simon Glass sjg@chromium.org
Applied to u-boot/master, thanks!
This check is simple, but IMHO, too simple. It will generate false-positive, or pointless, warnings for some common use cases. Say,
In an include header, #ifdef CONFIG_xxx extern int foo_data; int foo(void); #endif
We should try to avoid this in header files. But I sent a patch earlier today to turn off the check for header files and device tree.
Right, in a header that's a bad idea unless it's:
I'm not sure that it is a so bad idea; I think that it will detect some configuration error immediately rather than at the link time.
We prefer link time failures as -Werror is not the default in a regular build.
... #else static inline foo(void) {} #endif
Well, in this case, a corresponding C file often has a definition like: #ifdef CONFIG_xxx int foo(void) { ... } #endif
Right, and that's fine. But headers do not get guards around functions unless it's else-inline-to-nop-it-out.
Or in a C file (foo_common.c), #ifdef CONFIG_xxx_a int foo_a(void) ... #endif #ifdef CONFIG_xxx_b int foo_b(void) ... #endif
Perhaps the if() could be inside those functions in some cases?
Yeah, that's less clearly an example of something bad.
Again, I'm not sure that it is a bad idea. Such a use can be seen quite often in library code where there are many configurable options. The only way to avoid such a style of coding is that we would put each function into a separate C file even if it can be very small. It also requires more (common/helper) functions, which are essentially local to that library, to be declared as global.
Is this what you want?
It comes down to what the code reads best as, yes. A checkpatch error isn't a fatal you must fix it error. But you must be able to explain why it's wrong. And I think we're getting away from the main point here. Generally, #ifdef CONFIG_FOO .... #endif, in a function is ugly and we can do better. It also means better code analysis as I believe some tools will still evaluate if (0) { ... } but will not evaluate #if 0 ... #endif.
Or,
struct baa baa_list[] = { #ifdef CONFIG_xxx data_xxx, #endif
I'm not sure how to handle this one.
Rasmus' series to add CONFIG_IS_ENABLED(SYM, true, false) stuff would be handy here.
Ah, I didn't notice that. We can now have the code like: struct baa baa_list[] = { ... CONFIG_IS_ENABLED(xxx, (data_xxx,)) ... }
## I think the comma after 'data_xxx' is required, isn't it?
But what is the merit?
And, data_xxx itself has to be declared anyway like: #ifdef CONFIG_xxx struct baa data_xxx = { ... }; #endif
We _could_ have that yes, he's posted an RFC I need to reply to directly. As you would probably also need a __maybe_unused on the struct itself. Is that better?
...
They are harmless and can be ignored, but also annoying. Can you sophisticate this check?
Yes I agree we should avoid false negatives. It is better not to have a check than have one that is unreliable.
In addition, if I want to stick to this rule, there can co-exist an "old" style and "new" style of code in a single file. (particularly tons of examples in UEFI subsystem)
How should we deal with this?
Convert it?
Yes, code should be cleaned up and converted to using if (...) when possible. That we have new code that doesn't make use of this is because we didn't have tooling warning about when it wasn't used.
So if we want to add a new commit that complies with this rule while the file to which it will be applied has an old style of code, do you *require* that this existing file should be converted first in any case?
I honestly don't know. Is it a problem to look over the code and make use of if (IS_ENABLED(...)) { ... } when it would make the code read better and get better analysis?