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compiler warnung #66-D: enumeration value is out of "int" range

Gunnar Bohlen

Hello,
I'm getting many of this warning in my project which uses NXP header with enum definitions similat to this:

typedef enum _clock_attach_id
{
  kFRO12M_to_MAIN_CLK = MUX_A(CM_MAINCLKSELA, 0) | MUX_B(CM_MAINCLKSELB, 0),
  kNONE_to_NONE = 0x80000000UL,
} clock_attach_id_t;

The warning seems to be obvious because 0x80000000UL does not fit into int.

But the compiler manual v5.06 for µVision says about enum:


10.4 Structures, unions, enumeratons and bitfields in ARM C and C++

In C mode, and in C++ mode without --enum_is_int, if an enum contains only positive enumerator values, the storage type of the enum is the first unsigned type from the following list, according to the range of the enumerators in the enum. In other modes, and in cases where an enum contains any negative enumerator values, the storage type of the enum is the first of the following, according to the range of the
enumerators in the enum:
• unsigned char if not using --enum_is_int
• signed char if not using --enum_is_int
• unsigned short if not using --enum_is_int
• signed short if not using --enum_is_int
• signed int
• unsigned int except C with --strict
• signed long long except C with --strict
• unsigned long long except C with --strict

Maybe I misinterpret this, but I would think the compiler should choose "unsigned int" in this case. If so, why is there the warning?

The code works as expected, but I would like to minimize the number of warnings in the project (without code modification). Disableing this warning is also not good because it might hide a "real" problem.

Regards, Gunnar

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  • 0

    The problem is that enum constant is different from enumerated type. The paragraph from the manual that you posted, talks about the type of an enumeration and not the enum constant.

    AS per C99 standard, Section 6.7.2.2:

6.7.2.2 Enumeration specifiers
Syntax
1 enum-specifier:
enum identifieropt { enumerator-list }
enum identifieropt { enumerator-list , }
enum identifier
enumerator-list:
enumerator
enumerator-list , enumerator
enumerator:
enumeration-constant
enumeration-constant = constant-expression

Constraints
2 The expression that defines the value of an enumeration constant shall be an integer
constant expression that has a value representable as an int.

    It clearly mentions that the enum constant should have a value representable as an int. On a 32 bit machine int, the value 0x80000000 doesn't fit into an int and hence the warning.

    I am sorry but the behavior of your code is at the mercy of implementation and at best implementation defined.

Reply
  • 0

    The problem is that enum constant is different from enumerated type. The paragraph from the manual that you posted, talks about the type of an enumeration and not the enum constant.

    AS per C99 standard, Section 6.7.2.2:

6.7.2.2 Enumeration specifiers
Syntax
1 enum-specifier:
enum identifieropt { enumerator-list }
enum identifieropt { enumerator-list , }
enum identifier
enumerator-list:
enumerator
enumerator-list , enumerator
enumerator:
enumeration-constant
enumeration-constant = constant-expression

Constraints
2 The expression that defines the value of an enumeration constant shall be an integer
constant expression that has a value representable as an int.

    It clearly mentions that the enum constant should have a value representable as an int. On a 32 bit machine int, the value 0x80000000 doesn't fit into an int and hence the warning.

    I am sorry but the behavior of your code is at the mercy of implementation and at best implementation defined.

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