Re: [Patch v2 1/3] MdePkg/Include/IndustryStandard: Add Operator and Xor field names

["Pedro Falcato" <pedro.falcato@gmail.com>]

On Tue, May 30, 2023 at 7:53 PM Michael D Kinney
<michael.d.kinney@intel.com> wrote:
>
> Update Tpm12.h and Tpm20.h and not use c++ reserved keywords
> operator and xor in C structures to support use of these
> include files when building with a C++ compiler.
>
> This patch temporarily introduces an anonymous union to add
> Operator and Xor fields to support migration from the current
> field names to the new field names.
>
> Warning 4201 is disabled for VS20xx tool chains is a temporary
> change to allow the use of anonymous unions.
>
> Cc: Liming Gao <gaoliming@byosoft.com.cn>
> Cc: Zhiguang Liu <zhiguang.liu@intel.com>
> Cc: Oliver Smith-Denny <osde@linux.microsoft.com>
> Cc: Pedro Falcato <pedro.falcato@gmail.com>
> Cc: Aaron Pop <aaronpop@microsoft.com>
> Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
> ---
>  MdePkg/Include/IndustryStandard/Tpm12.h | 22 ++++++++++++++++++++--
>  MdePkg/Include/IndustryStandard/Tpm20.h | 25 +++++++++++++++++++++++--
>  2 files changed, 43 insertions(+), 4 deletions(-)
>
> diff --git a/MdePkg/Include/IndustryStandard/Tpm12.h b/MdePkg/Include/IndustryStandard/Tpm12.h
> index 155dcc9f5f99..56e89d9d0835 100644
> --- a/MdePkg/Include/IndustryStandard/Tpm12.h
> +++ b/MdePkg/Include/IndustryStandard/Tpm12.h
> @@ -9,6 +9,14 @@
>  #ifndef _TPM12_H_
>  #define _TPM12_H_
>
> +///
> +/// Temporary disable 4201 to support anonymous unions
> +///
> +#if defined (_MSC_EXTENSIONS)
> +#pragma warning( push )
> +#pragma warning ( disable : 4201 )
> +#endif
> +
>  ///
>  /// The start of TPM return codes
>  ///
> @@ -744,8 +752,11 @@ typedef struct tdTPM_PERMANENT_FLAGS {
>    BOOLEAN              TPMpost;
>    BOOLEAN              TPMpostLock;
>    BOOLEAN              FIPS;
> -  BOOLEAN                           operator;
> -  BOOLEAN                           enableRevokeEK;
> +  union {
> +    BOOLEAN            operator;
> +    BOOLEAN            Operator;
> +  };

Do you know if this works cleanly for the other toolchains? i.e
supported GCCs and CLANGs?
I don't *think* there's a warning for anonymous unions beyond passing
-pedantic + -std=c<something>, but it'd be good to know.
If so, we may need a pragma for this.

> +  BOOLEAN              enableRevokeEK;
>    BOOLEAN              nvLocked;
>    BOOLEAN              readSRKPub;
>    BOOLEAN              tpmEstablished;
> @@ -2162,4 +2173,11 @@ typedef struct tdTPM_RSP_COMMAND_HDR {
>
>  #pragma pack ()
>
> +///
> +/// Temporary disable 4201 to support anonymous unions
> +///
> +#if defined (_MSC_EXTENSIONS)
> +#pragma warning( pop )
> +#endif
> +
>  #endif
> diff --git a/MdePkg/Include/IndustryStandard/Tpm20.h b/MdePkg/Include/IndustryStandard/Tpm20.h
> index 4440f3769f26..a602c0d9c289 100644
> --- a/MdePkg/Include/IndustryStandard/Tpm20.h
> +++ b/MdePkg/Include/IndustryStandard/Tpm20.h
> @@ -15,6 +15,14 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
>
>  #include <IndustryStandard/Tpm12.h>
>
> +///
> +/// Temporary disable 4201 to support anonymous unions
> +///
> +#if defined (_MSC_EXTENSIONS)
> +#pragma warning( push )
> +#pragma warning ( disable : 4201 )
> +#endif
> +
>  #pragma pack (1)
>
>  // Annex A Algorithm Constants
> @@ -1247,7 +1255,10 @@ typedef union {
>    TPMI_AES_KEY_BITS    aes;
>    TPMI_SM4_KEY_BITS    SM4;
>    TPM_KEY_BITS         sym;
> -  TPMI_ALG_HASH     xor;
> +  union {
> +    TPMI_ALG_HASH      xor;
> +    TPMI_ALG_HASH      Xor;
> +  };
>  } TPMU_SYM_KEY_BITS;
>
>  // Table 123 - TPMU_SYM_MODE Union
> @@ -1320,7 +1331,10 @@ typedef struct {
>  // Table 136 - TPMU_SCHEME_KEYEDHASH Union
>  typedef union {
>    TPMS_SCHEME_HMAC    hmac;
> -  TPMS_SCHEME_XOR  xor;
> +  union {
> +    TPMS_SCHEME_XOR   xor;
> +    TPMS_SCHEME_XOR   Xor;
> +  };
>  } TPMU_SCHEME_KEYEDHASH;
>
>  // Table 137 - TPMT_KEYEDHASH_SCHEME Structure
> @@ -1809,4 +1823,11 @@ typedef struct {
>  #define HASH_ALG_SHA512   0x00000008
>  #define HASH_ALG_SM3_256  0x00000010
>
> +///
> +/// Temporary disable 4201 to support anonymous unions
> +///
> +#if defined (_MSC_EXTENSIONS)
> +#pragma warning( pop )
> +#endif
> +
>  #endif
> --
> 2.40.1.windows.1
>

All in all, this looks ok to me. Although I have to say, I'm not a
huge fan of the naming style inconsistency introduced here (i.e Xor vs
hmac).
What if we made all the struct members MixedCase? Or what if we did
something like calling them xor_ and operator_?

-- 
Pedro