Re: [PATCH v3] docs/misra: document the expected sizes of integer types

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Stefano,

> On 4 Apr 2024, at 03:12, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> 
> Xen makes assumptions about the size of integer types on the various
> architectures. Document these assumptions.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
> ---
> Changes in v3:
> - add links to System V, AAPCS32 and AAPCS64
> 
> ---
> docs/misra/C-language-toolchain.rst | 69 +++++++++++++++++++++++++++++
> 1 file changed, 69 insertions(+)
> 
> diff --git a/docs/misra/C-language-toolchain.rst 
> b/docs/misra/C-language-toolchain.rst
> index b7c2000992..84b21992bc 100644
> --- a/docs/misra/C-language-toolchain.rst
> +++ b/docs/misra/C-language-toolchain.rst
> @@ -480,4 +480,73 @@ The table columns are as follows:
>      - See Section "4.13 Preprocessing Directives" of GCC_MANUAL and Section 
> "11.1 Implementation-defined behavior" of CPP_MANUAL.
> 
> 
> +Sizes of Integer types
> +______________________
> +
> +Xen expects System V ABI on x86_64:
> +  https://gitlab.com/x86-psABIs/x86-64-ABI
> +
> +Xen expects AAPCS32 on ARMv8-A AArch32:
> +  https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst
> +
> +Xen expects AAPCS64 LP64 on ARMv8-A AArch64:
> +  https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst

We still support armv7 somehow so we should add something for it here.

> +
> +A summary table of data types, sizes and alignment is below:
> +
> +.. list-table::
> +   :widths: 10 10 10 45
> +   :header-rows: 1
> +
> +   * - Type
> +     - Size
> +     - Alignment
> +     - Architectures
> +
> +   * - char 
> +     - 8 bits
> +     - 8 bits
> +     - all architectures
> +
> +   * - short
> +     - 16 bits
> +     - 16 bits
> +     - all architectures
> +
> +   * - int
> +     - 32 bits
> +     - 32 bits
> +     - all architectures
> +
> +   * - long
> +     - 32 bits
> +     - 32 bits 
> +     - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32)

Same here armv7 should be mentioned.

> +
> +   * - long
> +     - 64 bits
> +     - 64 bits 
> +     - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64)
> +
> +   * - long long
> +     - 64-bit
> +     - 32-bit
> +     - x86_32
> +
> +   * - long long
> +     - 64-bit
> +     - 64-bit
> +     - 64-bit architectures, ARMv8-A AArch32, ARMv8-R AArch32

Should this be all architecture except x86_32 ?

> +
> +   * - pointer
> +     - 32-bit
> +     - 32-bit
> +     - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32)

Armv7 missing here.

> +
> +   * - pointer
> +     - 64-bit
> +     - 64-bit
> +     - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64)
> +
> +
> END OF DOCUMENT.
> -- 
> 2.25.1
> 

Cheers
Bertrand