[clang][enum_overflow]Clang incorrectly thinks that enumerators of enum does not fit in the largest integer type

[zhaojiangkun-1]

Test case:

enum E {
  e1 = 0xffffffffffffffff,
  e2, e3
} e = e3;

#define SA(I,X) int a##I[(X)? 1 : -1]

SA(1, sizeof(E) == sizeof(__int128));

Backtrace:

warning: incremented enumerator value 18446744073709551616 is not representable in the largest integer type [-Wenum-too-large]
  e2, e3
  ^
./ext1/int128-3.C:11:1: error: 'a1' declared as an array with a negative size
SA(1, sizeof(E) == sizeof(__int128));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./ext1/int128-3.C:9:26: note: expanded from macro 'SA'
#define SA(I,X) int a##I[(X)? 1 : -1]
                         ^~~~~~~~~~~
1 warning and 1 error generated.

It can be compiled in gcc, but an error is reported in clang.

https://godbolt.org/z/4Pdxs5sEs

This problem has been fixed before, but is it not compatible with this yet?
#24667

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (zhaojiangkun-1)

Test case: ``` enum E { e1 = 0xffffffffffffffff, e2, e3 } e = e3;

#define SA(I,X) int a##I[(X)? 1 : -1]

SA(1, sizeof(E) == sizeof(__int128));

Backtrace:

warning: incremented enumerator value 18446744073709551616 is not representable in the largest integer type [-Wenum-too-large]
e2, e3
^
./ext1/int128-3.C:11:1: error: 'a1' declared as an array with a negative size
SA(1, sizeof(E) == sizeof(__int128));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./ext1/int128-3.C:9:26: note: expanded from macro 'SA'
#define SA(I,X) int a##I[(X)? 1 : -1]
^~~~~~~~~~~
1 warning and 1 error generated.

It can be compiled in gcc, but an error is reported in clang.

https://godbolt.org/z/4Pdxs5sEs

This problem has been fixed before, but is it not compatible with this yet?
https://github.com/llvm/llvm-project/issues/24667

</details>

[hstk30-hw]

C99 6.7.2.2p2

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

C99 6.7.2.2p4

Each enumerated type shall be compatible with char, a signed integer type, or an
unsigned integer type. The choice of type is implementation-defined,108) but shall be
capable of representing the values of all the members of the enumeration.

llvm-project/clang/lib/Sema/SemaDecl.cpp

Lines 19700 to 19711 in 060d62b

	// If we're not in C++, diagnose the overflow of enumerator values,
	// which in C99 means that the enumerator value is not representable in
	// an int (C99 6.7.2.2p2). However C23 permits enumerator values that
	// are representable in some larger integral type and we allow it in
	// older language modes as an extension.
	// Exclude fixed enumerators since they are diagnosed with an error for
	// this case.
	if (!getLangOpts().CPlusPlus && !T.isNull() && !Enum->isFixed())
	Diag(IdLoc, getLangOpts().C23
	? diag::warn_c17_compat_enum_value_not_int
	: diag::ext_c23_enum_value_not_int)
	<< 1 << toString(EnumVal, 10) << 1;