Re: [edk2-devel] VariablePolicy: Final Changes Thread 2 - ECC & UnitTest

["Michael D Kinney" <michael.d.kinney@intel.com>]

Hi Laszlo,

Option #3 looks really good to me.  And I agree that ECC should not generate 
an error if a STATIC CONST local variable is initialized.

Thanks,

Mike

> -----Original Message-----
> From: Laszlo Ersek <lersek@redhat.com>
> Sent: Wednesday, October 7, 2020 6:43 AM
> To: devel@edk2.groups.io; Kinney, Michael D <michael.d.kinney@intel.com>; Bret Barkelew <Bret.Barkelew@microsoft.com>
> Subject: Re: [edk2-devel] VariablePolicy: Final Changes Thread 2 - ECC & UnitTest
> 
> On 10/07/20 03:46, Michael D Kinney wrote:
> >
> > Bret,
> >
> > Initializing variable in declaration for structures and arrays
> > introduces use of intrinsics.  Since it is possible for unit test
> > sources to be used for both host and target tests, I recommend we
> > continue to follow the EDK II coding style for unit tests to support
> > maximum compatibility and code reuse.
> >
> > Using a module global variable with initializers instead of
> > initializing a local declaration is the same amount of work, so I do
> > not believe that will result in fewer tests.
> >
> > I agree it is useful to have the test data next to the test code. This
> > can be accomplished by breaking up into more files so the test data is
> > immediately above the test function the test data is used.  Does ECC
> > raise an error if a module global is placed between 2 functions?  A
> > 2nd approach to put the module global immediately above the test
> > function the test data is used.
> 
> Consider the following example structure type, for the sake of
> discussion:
> 
>   typedef struct {
>     UINT32 Value;
>   } TEST_DATA;
> 
> 
> * Case#1: block scope, automatic storage duration
> 
>   EFI_STATUS
>   FoobarTest (
>     VOID
>     )
>   {
>     TEST_DATA TestData = { 42 };
>     // ...
>   }
> 
> Problem: uses intrinsics.
> 
> 
> * Case#2: file scope, static storage duration.
> 
>   STATIC CONST TEST_DATA mTestData = { 42 };
> 
>   EFI_STATUS
>   FoobarTest (
>     VOID
>     )
>   {
>     // ...
>   }
> 
> Problem: either "mTestData" is textually far from FoobarTest(), or -- if
> we keep them close to each other -- we mix variable definitions with
> function definitions, at file scope.
> 
> 
> * Case #3: block scope, static storage duration.
> 
>   EFI_STATUS
>   FoobarTest (
>     VOID
>     )
>   {
>     STATIC CONST TEST_DATA TestData = { 42 };
>     // ...
>   }
> 
> Problem: there should be none. Does not involve intrinsics, and the
> object definition is part of the function's scope.
> 
> 
> If ECC does not recognize case#3 as valid, then that is an *ECC bug*.
> 
> ECC has no reason to prevent case#3, as case#3 does not involve
> intrinsics, and is a generally valid and useful C language construct (it
> combines the life cycle of case#2 with the visibility of case#1).
> 
> Again, if ECC rejects case#3, that's *definitely* a bug in ECC, and we
> should fix it first. Given that ECC includes a full-blown C language
> parser, the fix should not be too difficult -- check if the declaration
> has the "static" storage-class specifier.
> 
> ... In fact, I think that purely CONST-qualifying TestData might suffice
> for shutting up ECC. See the following in
> "BaseTools/Source/Python/Ecc/c.py", method
> "CheckFuncLayoutLocalVariable":
> 
> >         for Result in ResultSet:
> >             if len(Result[1]) > 0 and 'CONST' not in Result[3]:
> >                 PrintErrorMsg(ERROR_C_FUNCTION_LAYOUT_CHECK_NO_INIT_OF_VARIABLE, 'Variable Name: %s' % Result[0], FileTable,
> Result[2])
> 
> So case#3 should work through that avenue already, because case#3 has
> CONST *too*.
> 
> Now, in case#3, if "TestData" needs to undergo modifications, and so
> CONST is not immediately desirable, that's solvable:
> 
>   EFI_STATUS
>   FoobarTest (
>     VOID
>     )
>   {
>     STATIC CONST TEST_DATA TestDataTemplate = { 42 };
>     TEST_DATA TestData;
> 
>     CopyMem (&TestData, TestDataTemplate, sizeof (TEST_DATA));
>     // ...
>   }
> 
> Thanks
> Laszlo
> 
> >
> > Best regards,
> >
> > Mike
> >
> > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Bret Barkelew via groups.io
> > Sent: Tuesday, October 6, 2020 5:28 PM
> > To: devel@edk2.groups.io
> > Subject: [edk2-devel] VariablePolicy: Final Changes Thread 2 - ECC & UnitTest
> >
> > I\x19ve worked through all the ECC issues with Variable Policy (AND the UnitTests) on this branch:
> > Commits · corthon/edk2 (github.com)<https://github.com/corthon/edk2/commits/var_policy_dev_submission_v8>
> >
> > I even wrote the Main() entry point lib that Laszlo suggested (it works rather nicely):
> > TEMP: Staging for HostTest entry point · corthon/edk2@4ce5210
> (github.com)<https://github.com/corthon/edk2/commit/4ce52108b3e1bcb2ba78995be94c3949fe647eda>
> >
> > However, there\x19s one that I just can\x19t get past and I would like to take it up with the community. I don\x19t think that UnitTests
> should have to deal with the \x1ccan\x19t initialize variables in declaration\x1d check. Almost none of the solutions that I tested worked,
> and the ones that did were too cumbersome. They failed on two key points that are important for test writing:
> >
> >   *   They were annoying to write ===> fewer tests.
> >   *   They moved even more of the test case data away from the test ===> harder to read tests.
> >
> > I would like to move for an exception for unit tests (or at least host-based unit tests), but I don\x19t know how to accomplish that
> from a technical standpoint.
> >
> > Thoughts?
> >
> > - Bret
> >
> >
> >
> >
> > 
> >
> >