Nikolai,
Based Section 2.3 of the UEFI Spec section on Calling Convention and Data
Types, my proposed code change for compatibility should use UINT32 instead of
UINTN:
if ((PoolType >= EfiMaxMemoryType && (UINT32)PoolType <= 0x7fffffff) ||
Does this code change resolve the clang compiler warning/error?
UEFI Spec defines EFI_MEMORY_TYPE as an enum, and ANSI C allows compilers to
have flexibility for enums to be signed or unsigned. Details from UEFI Spec
shown below. This means we cannot change the declaration of EFI_MEMORY_TYPE to
be a UINT32 and we cannot make any assumptions about EFI_MEMORY_TYPE being
signed or unsigned.
UEFI Specification Section 6.2 - Memory Allocation Services - AllocatePages()
defines EFI_MEMORY_TYPE to be an enum.:
//*******************************************************
//EFI_MEMORY_TYPE
//*******************************************************
// These type values are discussed in Table 24 and Table 25.
typedef enum {
EfiReservedMemoryType,
EfiLoaderCode,
EfiLoaderData,
EfiBootServicesCode,
EfiBootServicesData,
EfiRuntimeServicesCode,
EfiRuntimeServicesData,
EfiConventionalMemory,
EfiUnusableMemory,
EfiACPIReclaimMemory,
EfiACPIMemoryNVS,
EfiMemoryMappedIO,
EfiMemoryMappedIOPortSpace,
EfiPalCode,
EfiMaxMemoryType
} EFI_MEMORY_TYPE;
UEFI Specification Section 2.3.1 - Data Types - Table 6 has the following entry
for enumerated types:
<Enumerated Type>
Element of a standard ANSI C enum type declaration. Type INT32 or
UINT32.
ANSI C does not define the size of sign of an enum so they should never
be used in
structures. ANSI C integer promotion rules make INT32 or UINT32
interchangeable
when passed as an argument to a function.
The issue is that some compilers treat enums as signed and others as unsigned.
The EDK II implementation attempts to be compatible with both types of
compilers.
Best regards,
Mike
-----Original Message-----
From: Nikolai Saoukh [mailto:n...@otdel-1.org]
Sent: Friday, January 11, 2013 9:32 AM
To: edk2-devel@lists.sourceforge.net
Subject: Re: [edk2] clang compilation error
Well, what is wrong with UINT32 as type for EFI_MEMORY_TYPE?
Why EFI_MEMORY_TYPE should be signed?
On Fri, Jan 11, 2013 at 9:00 PM, Kinney, Michael D
<michael.d.kin...@intel.com> wrote:
> Sergey,
>
>
>
> The comparison against 0x7fffffff is required due to a UEFI Spec
> requirement. UEFI Specification 2.3.1 Section 6.2 AllocatePages() and
> AllocatePool() both have a MemoryType parameter that is defined as follows:
>
>
>
> MemoryType
>
>
>
> The type of memory to allocate. The type EFI_MEMORY_TYPE is defined in
> “Related Definitions” below. These memory types are also described in more
> detail in Table 24 and Table 25. Normal allocations (that is, allocations by
> any UEFI application) are of type EfiLoaderData. MemoryType values in the
> range 0x80000000..0xFFFFFFFF are reserved for use by UEFI OS loaders that
> are provided by operating system vendors. The only illegal memory type
> values are those in the range EfiMaxMemoryType..0x7FFFFFFF.
>
>
>
> Since we have to be compatible with both 32-bit and 64-bit CPUs, we cannot
> implement logic that depends on an enum being a 32-bit signed value.
>
>
>
> There are two ways to address this compiler error:
>
>
>
> 1) Disable this compiler warning for this one compiler in tools_def.txt
>
> 2) Update the sources to perform an unsigned comparison such as:
>
>
>
> if ((PoolType >= EfiMaxMemoryType && (UINTN)PoolType <= 0x7fffffff) ||
>
> Best regards,
>
>
>
> Mike
>
>
>
> From: Sergey Isakov [mailto:isakov...@bk.ru]
> Sent: Friday, January 11, 2013 2:15 AM
> To: edk2-devel@lists.sourceforge.net
> Subject: Re: [edk2] clang compilation error
>
>
>
> Ok, UEFI spec is wrong and as we have to follow them we should exclude the
> comparison.
>
>
>
> 11.01.2013, в 11:58, Tim Lewis написал(а):
>
>
>
> Sergey –
>
>
>
> It is an enum in the UEFI specification.
>
>
>
> Why not just remove the second comparison? Since the enum is an int (for
> UEFI cases), if it is more than or equal to EfiMaxMemoryType, it must be
> less than 0x7fffffff (if it is an int). Otherwise it would be less than 0.
>
>
>
> Tim
>
>
>
> From: Sergey Isakov [mailto:isakov...@bk.ru]
> Sent: Thursday, January 10, 2013 11:54 PM
> To: edk2-devel@lists.sourceforge.net
> Subject: [edk2] clang compilation error
>
>
>
> Hi,
>
> with clang 3.3 one has the follow
>
> ----------
>
> /edk2/MdeModulePkg/Core/Dxe/Mem/Pool.c:188:49: error: comparison of constant
> 2147483647 with expression of type 'EFI_MEMORY_TYPE' is always true
> [-Werror,-Wtautological-constant-out-of-range-compare] if ((PoolType >=
> EfiMaxMemoryType && PoolType <= 0x7fffffff) ||
> ~~~~~~~~ ^ ~~~~~~~~~~
> 1 error generated.
>
> ----------
>
> Again, it is enum and sholud not be compared.
>
> I will propose to make this as UINT32 and change enum list by a set of
> definitions like
>
> #define EfiACPIMemoryNVS 0x0A
>
>
>
> It will be better then mix enum and integer.
>
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