On 06/25/20 09:59, PierreGondois wrote:
> From: Pierre Gondois <pierre.gond...@arm.com>
>
> While building with the following command line:
> build -b DEBUG -a AARCH64 -t VS2017 -p
> edk2\MdeModulePkg\MdeModulePkg.dsc
>
> A missing cast triggers the following warning,
> then triggering an error:
> edk2/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c(652):
> warning C4152: nonstandard extension, function/data pointer
> conversion in expression
>
> This patch adds a cast, removing the warning.
>
> Signed-off-by: Pierre Gondois <pierre.gond...@arm.com>
> ---
>
> The changes can be seen at:
> https://github.com/PierreARM/edk2/commits/831_Fix_implicit_cast_v1
>
> Notes:
> v1:
> - Add (void*) cast. [Pierre]
>
> ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> index
> 222ff817956feb738325fc78fbaf064de98802a9..7df7c75d4a571403209e4fee0f0a06ed6e3513fa
> 100644
> --- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> +++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
> @@ -649,7 +649,7 @@ ArmMmuBaseLibConstructor (
> // The ArmReplaceLiveTranslationEntry () helper function may be invoked
> // with the MMU off so we have to ensure that it gets cleaned to the PoC
> //
> - WriteBackDataCacheRange (ArmReplaceLiveTranslationEntry,
> + WriteBackDataCacheRange ((VOID*)ArmReplaceLiveTranslationEntry,
> ArmReplaceLiveTranslationEntrySize);
>
> return RETURN_SUCCESS;
>
Converting a pointer-to-function to a pointer-to-void (or
pointer-to-object, or pointer-to-incomplete-type) is not defined by the
C standard. So if we want to fix this warning cleanly, we should convert
first to UINTN, and then to (VOID*).
Because (from C99, 6.3.2.3 Pointers):
6 Any pointer type may be converted to an integer type. Except as
previously specified, the result is implementation-defined. If the
result cannot be represented in the integer type, the behavior is
undefined. The result need not be in the range of values of any
integer type.
and
5 An integer may be converted to any pointer type. Except as
previously specified, the result is implementation-defined, might
not be correctly aligned, might not point to an entity of the
referenced type, and might be a trap representation. [56]
Footnote 56: The mapping functions for converting a pointer to an
integer or an integer to a pointer are intended to be
consistent with the addressing structure of the execution
environment.
So when we write (VOID*)(UINTN)ArmReplaceLiveTranslationEntry, then we
get a pass at least as "implementation-defined".
Thanks,
Laszlo
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