Re: [edk2] tautological-constant-out-of-range-compare

Subject: Re: [edk2] tautological-constant-out-of-range-compare

From: Isakov Sergey <isakov-sl@bk.ru>

To: edk2-devel@lists.sourceforge.net

Date: 2013-01-21 08:42:11

Hi,
If we will always cast enum to UINT32 then in your sample we get e_s_neg > e_s_pos
while without cast e_s_neg < e_s_pos.
It is not a method to work. 
EFI_MEMORY_TYPE must be defined as INT32 but not questionable enum.

Sergey

On 21.01.2013, at 0:18, Joe Vernaci wrote:

Hi Nikolai,

I think your recast as a UINT32 is the correct change.  From the UEFI spec 6.2 when allocating "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."

ANSI and ISO C state that named enumeration constants must be type (signed) int but may be physically stored as either signed int or unsigned int which is implementation specific (ISO 9998:201x 6.7.2.2).  Some people interpret this as enums must always be signed int.  However the norm seems to be treat it as unsigned unless a negative constant is used in the enum definition.  If your compiler is treating this enum as a signed int then yes PoolType will always be less than 0x7fffffff.  If you have not changed the EFI_MEMORY_TYPE definition using a negative I'm not sure why it is doing this.

Here is a simple example:
#include <stdio.h>

typedef enum {
    e_s_neg_1 = -1,  // <-- valid
    e_s_pos_1 = 1,
    e_s_pos_2 = 2
} e_s;

typedef enum {
    e_u_pos_1 = 1,
    e_u_pos_2 = 2
} e_u;

typedef enum {
    e_und_0,
    e_und_pos_1
} e_und;

typedef enum {
    e_inv_pos_1 = 1,
    e_inv_pos_2 = 2,
    e_inv_neg_1 = 0xffffffff  // <-- invalid but same value as (-1)
} e_inv;

void func_s(e_s e) {
    if (e <= 0x7fffffff) {  // <-- should use test/jns or cmp/jg
        printf("func_s: 0x%08x\n", e);
    }
}

void func_u(e_u e) {
    if (e <= 0x7fffffff) {  // <-- should use test/js or cmp/ja
        printf("func_u: 0x%08x\n", e);
    }
}

void func_und(e_und e) {
    if (e <= 0x7fffffff) {  // <-- should use test/js or cmp/ja
        printf("func_und: 0x%08x\n", e);
    }
}

void func_inv(e_inv e) {
    if (e <= 0x7fffffff) {  // <-- should use test/js or cmp/ja
        printf("func_inv: 0x%08x\n", e);
    }
}

int main(int argc, char **argv) {
    func_s(-1);  // <-- only function that should print
    func_u(-1);
    func_und(-1);
    func_inv(-1);
    return 0;
}

--Joe

On Sat, Jan 19, 2013 at 1:19 AM, Nikolai Saoukh <nms@otdel-1.org> wrote:
I just added handcrafted toolchain (ELFCLANG) to Conf/tools_def.txt.
And tried to compile DuetPkg -- DEBUG & IA32. Command lines follows

"clang" -ffreestanding -m32 -fshort-wchar -fno-strict-aliasing -Wall
-c -include /tiano/edk2/Build/DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/DEBUG/AutoGen.h
-D
STRING_ARRAY_NAME=DxeCoreStrings -o
/tiano/edk2/Build/DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/OUTPUT/Mem/Pool.obj
-I/tiano/edk2/MdeModulePkg/Core/Dxe/DxeMain
 -I/tiano/edk2/MdeModulePkg/Core/Dxe/Dispatcher
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Event
-I/tiano/edk2/MdeModulePkg/Core/Dxe/FwVol
-I/tiano/edk2/MdeModulePkg/Core/Dxe/FwVolBlock
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Mem
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Gcd
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Hand
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Library -I/tiano/edk2/
MdeModulePkg/Core/Dxe/Misc -I/tiano/edk2/MdeModulePkg/Core/Dxe/Image
-I/tiano/edk2/MdeModulePkg/Core/Dxe/SectionExtraction
-I/tiano/edk2/MdeModulePkg/Core/Dxe -I/tiano/edk2/Build/
DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/DEBUG
-I/tiano/edk2/MdePkg -I/tiano/edk2/MdePkg/Include
-I/tiano/edk2/MdePkg/Include/Ia32 -I/tiano/edk2/MdeModulePkg
-I/tiano/edk2/MdeModulePkg/Include /tiano/edk2/MdeModulePkg/Core/Dxe/Mem/Pool.c
/tiano/edk2/MdeModulePkg/Core/Dxe/Mem/Pool.c:188:49: warning:
comparison of constant 2147483647 with expression of type
'EFI_MEMORY_TYPE' is always true [-Wtautological-constant-o
ut-of-range-compare]
  if ((PoolType >= EfiMaxMemoryType && PoolType <= 0x7fffffff) ||
                                       ~~~~~~~~ ^  ~~~~~~~~~~
1 warning generated.
"echo" Symbol renaming not needed for
/tiano/edk2/Build/DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/OUTPUT/Mem/Pool.obj
Symbol renaming not needed for
/tiano/edk2/Build/DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/OUTPUT/Mem/Pool.obj
"clang" -ffreestanding -m32 -fshort-wchar -fno-strict-aliasing -Wall
-c -include /tiano/edk2/Build/DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/DEBUG/AutoGen.h
-DSTRING_ARRAY_NAME=DxeCoreStrings -o
/tiano/edk2/Build/DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/OUTPUT/Mem/Page.obj
-I/tiano/edk2/MdeModulePkg/Core/Dxe/DxeMain
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Dispatcher
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Event
-I/tiano/edk2/MdeModulePkg/Core/Dxe/FwVol
-I/tiano/edk2/MdeModulePkg/Core/Dxe/FwVolBlock
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Mem
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Gcd
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Hand
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Library
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Misc
-I/tiano/edk2/MdeModulePkg/Core/Dxe/Image
-I/tiano/edk2/MdeModulePkg/Core/Dxe/SectionExtraction
-I/tiano/edk2/MdeModulePkg/Core/Dxe
-I/tiano/edk2/Build/DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/DEBUG
-I/tiano/edk2/MdePkg -I/tiano/edk2/MdePkg/Include
-I/tiano/edk2/MdePkg/Include/Ia32 -I/tiano/edk2/MdeModulePkg
-I/tiano/edk2/MdeModulePkg/Include
/tiano/edk2/MdeModulePkg/Core/Dxe/Mem/Page.c
/tiano/edk2/MdeModulePkg/Core/Dxe/Mem/Page.c:528:40: warning:
comparison of constant 2147483647 with expression of type
'EFI_MEMORY_TYPE' is always true
[-Wtautological-constant-out-of-range-compare]
  if (Type >= EfiMaxMemoryType && Type <= 0x7fffffff) {
                                  ~~~~ ^  ~~~~~~~~~~
/tiano/edk2/MdeModulePkg/Core/Dxe/Mem/Page.c:1101:53: warning:
comparison of constant 2147483647 with expression of type
'EFI_MEMORY_TYPE' is always true
[-Wtautological-constant-out-of-range-compare]
  if ((MemoryType >= EfiMaxMemoryType && MemoryType <= 0x7fffffff) ||
                                         ~~~~~~~~~~ ^  ~~~~~~~~~~
2 warnings generated.
"echo" Symbol renaming not needed for
/tiano/edk2/Build/DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/OUTPUT/Mem/Page.obj
Symbol renaming not needed for
/tiano/edk2/Build/DuetPkgIA32/DEBUG_ELFCLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/OUTPUT/Mem/Page.obj


On Wed, Jan 16, 2013 at 6:21 AM, Tian, Feng <feng.tian@intel.com> wrote:
> Hi, Saoukh
>
>
>
> What tool-chain and build option are you using? Are you changing
> tools_def.txt in Conf directory?
>
> Could you paste the entire command line of building this .c file to us?
>
>
>
> Thanks
>
> Feng
>
>
>
> From: Nikolai Saoukh [mailto:nms@otdel-1.org]
> Sent: Tuesday, January 15, 2013 22:27
>
>
> To: edk2-devel@lists.sourceforge.net
> Subject: [edk2] tautological-constant-out-of-range-compare
>
>
>
> This particular case was discussed already
>
>
>
> /tiano/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) ||
>
>                                        ~~~~~~~~ ^  ~~~~~~~~~~
>
>
>
> /tiano/edk2/MdeModulePkg/Core/Dxe/Mem/Page.c:528:40: error: comparison of
> constant 2147483647 with expression of type 'EFI_MEMORY_TYPE' is always true
> [-Werror,-Wtautological-constant-out-of-range-compare]
>
>   if (Type >= EfiMaxMemoryType && Type <= 0x7fffffff) {
>
>                                   ~~~~ ^  ~~~~~~~~~~
>
>
>
> .................
>
>
>
> "i686-pc-mingw32-objcopy" --redefine-sym _memcpy=_CopyMem --redefine-sym
> _memset=_SetMem
> /tiano/edk2/Build/DuetPkgIA32/DEBUG_PECLANG/IA32/MdeModulePkg/Core/Dxe/DxeMain/OUTPUT/Mem/Pool.obj
>
> /tiano/edk2/MdeModulePkg/Core/Dxe/Mem/Page.c:1101:53: error: comparison of
> constant 2147483647 with expression of type 'EFI_MEMORY_TYPE' is always true
> [-Werror,-Wtautological-constant-out-of-range-compare]
>
>   if ((MemoryType >= EfiMaxMemoryType && MemoryType <= 0x7fffffff) ||
>
>                                          ~~~~~~~~~~ ^  ~~~~~~~~~~
>
>
>
>
>
> I guess it should be written like this
>
>
>
> if ((PoolType >= EfiMaxMemoryType && ((UINT32)PoolType <= 0x7fffffff)) ...
>
>
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