[edk2-devel] [PATCH v2 1/1] MdePkg: Add STATIC_ASSERT macro

Thu Aug 15 01:59:04 UTC 2019

Vitaly:
  As you know, edk2 201908 stable tag will start soft freeze tomorrow. Dose this patch plan to catch this stable tag?
 If yes, please ask the feedback from Tianocore Stewards. I have cc this patch to all Stewards.

Thanks
Liming
From: devel at edk2.groups.io [mailto:devel at edk2.groups.io] On Behalf Of Yao, Jiewen
Sent: Thursday, August 15, 2019 9:05 AM
To: devel at edk2.groups.io; vit9696 at protonmail.com; Kinney, Michael D <michael.d.kinney at intel.com>
Cc: Laszlo Ersek <lersek at redhat.com>
Subject: Re: [edk2-devel] [PATCH v2 1/1] MdePkg: Add STATIC_ASSERT macro

Good input.
I think we should separate the work to convert all EDKII code to use STATIC_ASSERT.
We can do that work once we add STATIC_ASSERT.

I recommend:

1)      Step 1: Add STATIS_ASSERT - this patch and this Bugzilla

2)      Step 2: Convert VERIFY_SIZE_OF to STATIS_ASSERT, and remove VERIFY_SIZE_OF – the other patch and the other Bugzilla

3)      Step 3: Scan the rest, if there is need. – Another patch and another Bugzilla

Thank you
Yao Jiewen

From: devel at edk2.groups.io<mailto:devel at edk2.groups.io> [mailto:devel at edk2.groups.io] On Behalf Of Vitaly Cheptosv via Groups.Io
Sent: Thursday, August 15, 2019 12:23 AM
To: Kinney, Michael D <michael.d.kinney at intel.com<mailto:michael.d.kinney at intel.com>>
Cc: devel at edk2.groups.io<mailto:devel at edk2.groups.io>; Laszlo Ersek <lersek at redhat.com<mailto:lersek at redhat.com>>
Subject: Re: [edk2-devel] [PATCH v2 1/1] MdePkg: Add STATIC_ASSERT macro

Michael, Liming, Laszlo,

Static assertions via _Static_assert are standard C11 functionality, thus any at least C11 (ISO/IEC 9899 2011) conforming compiler is required to support the second argument with the diagnostic description.

The notation without the message currently is only present in C++, not in C, thus the two-argument notation is the only allowed notation for _Static_assert for at least C17 (ISO/IEC 9899 2018) and below.

In the bottom of this message I included a quote from C17 for the relevant section (6.7.10).

GCC and CLANG (including Xcode) appear to be conforming to the standard for this section, and MSVC compiler static_assert extension also supports the diagnostic message argument. This is pretty much all we care about.

As for examples, I see little reason to clarify STATIC_ASSERT behaviour outside of the standard reference in its description and actual usage in the source code, but can do that just fine if you think that it may help somebody.

I fully agree that VERIFY_SIZE_OF usage should be converted to STATIC_ASSERT, and in fact I also suggest VERIFY_SIZE_OF to be entirely removed from Base.h. This should be fairly costless, as apparently it is only used in Base.h and MdeModulePkg/Library/ResetUtilityLib/ResetUtility.c, which I can replace in the same patch set.

As for select ASSERT usage switching to STATIC_ASSERT, this would also be great, as let us be honest, the use of ASSERT in EDK II codebase is very questioning. In fact, this was one of the reasons we introduced our own static assertions some time ago. However, fixing up all broken assertions is unlikely a best place to fit into this patchset, but I can surely add a few examples, in case somebody points them out. This will be useful for reference purposes and may help the maintainers to get a better idea when static assertions are to be used.

Looking forward to hearing your opinions.

Best regards,
Vitaly

6.7.10 Static assertions

Syntax
1 static_assert-declaration:
_Static_assert ( constant-expression , string-literal ) ;

Constraints
2 The constant expression shall compare unequal to 0.

Semantics
3 The constant expression shall be an integer constant expression. If the value of the constant expression compares unequal to 0, the declaration has no effect. Otherwise, the constraint is violated and the implementation shall produce a diagnostic message that includes the text of the string literal, except that characters not in the basic source character set are not required to appear in the message.

Forward references: diagnostics (7.2).

7.2 Diagnostics <assert. h>

3 The macro
static_assert
expands to _Static_assert.

> 14 авг. 2019 г., в 18:47, Kinney, Michael D <michael.d.kinney at intel.com<mailto:michael.d.kinney at intel.com>> написал(а):
>
>
> Liming,
>
> I think a good candidate to demonstrate this
> feature are the checks made in MdePkg/Include/Base.h.
> The current implementation forces a divide by 0
> in the C pre-processor to break the build.
> STATIC_ASSERT() would be a better way to do this.
> I would also remove unused externs from the builds.
>
> /**
>  Verifies the storage size of a given data type.
>
>  This macro generates a divide by zero error or a zero size array declaration in
>  the preprocessor if the size is incorrect.  These are declared as "extern" so
>  the space for these arrays will not be in the modules.
>
>  @param  TYPE  The date type to determine the size of.
>  @param  Size  The expected size for the TYPE.
>
> **/
> #define VERIFY_SIZE_OF(TYPE, Size) extern UINT8 _VerifySizeof##TYPE[(sizeof(TYPE) == (Size)) / (sizeof(TYPE) == (Size))]

>
> //
> // Verify that ProcessorBind.h produced UEFI Data Types that are compliant with
> // Section 2.3.1 of the UEFI 2.3 Specification.
> //
> VERIFY_SIZE_OF (BOOLEAN, 1);
> VERIFY_SIZE_OF (INT8, 1);
> VERIFY_SIZE_OF (UINT8, 1);
> VERIFY_SIZE_OF (INT16, 2);
> VERIFY_SIZE_OF (UINT16, 2);
> VERIFY_SIZE_OF (INT32, 4);
> VERIFY_SIZE_OF (UINT32, 4);
> VERIFY_SIZE_OF (INT64, 8);
> VERIFY_SIZE_OF (UINT64, 8);
> VERIFY_SIZE_OF (CHAR8, 1);
> VERIFY_SIZE_OF (CHAR16, 2);
>
> //
> // The following three enum types are used to verify that the compiler
> // configuration for enum types is compliant with Section 2.3.1 of the
> // UEFI 2.3 Specification. These enum types and enum values are not
> // intended to be used. A prefix of '__' is used avoid conflicts with
> // other types.
> //
> typedef enum {
>  __VerifyUint8EnumValue = 0xff
> } __VERIFY_UINT8_ENUM_SIZE;
>
> typedef enum {
>  __VerifyUint16EnumValue = 0xffff
> } __VERIFY_UINT16_ENUM_SIZE;
>
> typedef enum {
>  __VerifyUint32EnumValue = 0xffffffff
> } __VERIFY_UINT32_ENUM_SIZE;
>
> VERIFY_SIZE_OF (__VERIFY_UINT8_ENUM_SIZE, 4);
> VERIFY_SIZE_OF (__VERIFY_UINT16_ENUM_SIZE, 4);
> VERIFY_SIZE_OF (__VERIFY_UINT32_ENUM_SIZE, 4);
>
> A couple examples.  Do all the compilers support the message parameter too?
>
> STATIC_ASSERT (sizeof (BOOLEAN) == 1, "sizeof (BOOLEAN) does not meet UEFI Specification Data Type requirements")
> STATIC_ASSERT (sizeof (UINT16)  == 2, "sizeof (UINT16) does not meet UEFI Specification Data Type requirements")
> STATIC_ASSERT (sizeof (INT32)   == 4, "sizeof (INT32) does not meet UEFI Specification Data Type requirements")
> STATIC_ASSERT (sizeof (CHAR16)  == 2, "sizeof (CHAR16) does not meet UEFI Specification Data Type requirements")
> STATIC_ASSERT (sizeof (__VERIFY_UINT8_ENUM_SIZE) == 4, "Size of enum does not meet UEFI Specification Data Type requirements")

> STATIC_ASSERT (sizeof (__VERIFY_UINT32_ENUM_SIZE) == 4, "Size of enum does not meet UEFI Specification Data Type requirements")

>
> Thanks,
>
> Mike
>
>> -----Original Message-----
>> From: devel at edk2.groups.io<mailto:devel at edk2.groups.io> [mailto:devel at edk2.groups.io]
>> On Behalf Of Liming Gao
>> Sent: Wednesday, August 14, 2019 6:50 AM
>> To: devel at edk2.groups.io<mailto:devel at edk2.groups.io>; vit9696 at protonmail.com<mailto:vit9696 at protonmail.com>
>> Subject: Re: [edk2-devel] [PATCH v2 1/1] MdePkg: Add
>> STATIC_ASSERT macro
>>
>> Can you add the sample usage of new macro STATIC_ASSERT?
>>
>> Or, give the link of static_assert or _Static_assert.
>>
>> If so, the developer knows how to use them in source
>> code.
>>
>> Thanks
>> Liming
>>> -----Original Message-----
>>> From: devel at edk2.groups.io<mailto:devel at edk2.groups.io>
>> [mailto:devel at edk2.groups.io] On Behalf Of
>>> vit9696 via Groups.Io
>>> Sent: Tuesday, August 13, 2019 4:17 PM
>>> To: devel at edk2.groups.io<mailto:devel at edk2.groups.io>
>>> Subject: [edk2-devel] [PATCH v2 1/1] MdePkg: Add
>> STATIC_ASSERT macro
>>>
>>>
>> REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2048
>>>
>>> Provide a macro for compile time assertions.
>>> Equivalent to C11 static_assert macro from assert.h.
>>>
>>> Signed-off-by: Vitaly Cheptsov
>> <vit9696 at protonmail.com<mailto:vit9696 at protonmail.com>>
>>> ---
>>> MdePkg/Include/Base.h | 11 +++++++++++
>>> 1 file changed, 11 insertions(+)
>>>
>>> diff --git a/MdePkg/Include/Base.h
>> b/MdePkg/Include/Base.h index
>>> ce20b5f01dce..f85f7028a262 100644
>>> --- a/MdePkg/Include/Base.h
>>> +++ b/MdePkg/Include/Base.h
>>> @@ -843,6 +843,17 @@ typedef UINTN  *BASE_LIST;
>> #define
>>> OFFSET_OF(TYPE, Field) ((UINTN) &(((TYPE *)0)->Field))
>> #endif
>>>
>>> +///
>>> +/// Portable definition for compile time assertions.
>>> +/// Equivalent to C11 static_assert macro from
>> assert.h.
>>> +/// Takes condtion and error message as its
>> arguments.
>>> +///
>>> +#ifdef _MSC_EXTENSIONS
>>> +  #define STATIC_ASSERT static_assert #else
>>> +  #define STATIC_ASSERT _Static_assert #endif
>>> +
>>> /**
>>>   Macro that returns a pointer to the data structure
>> that contains a specified field of
>>>   that data structure.  This is a lightweight method
>> to hide
>>> information by placing a
>>> --
>>> 2.20.1 (Apple Git-117)
>>>
>>>
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