Fix: Under Clang compilation constexpr variable 'INVALID_HANDLE' must be initialized by a constant expression

[Khalyutin]

The compiler does not consider "#define INVALID_HANDLE_VALUE ((HANDLE)(LONG_PTR)-1)" as a constant - compilation error: constexpr variable 'INVALID_HANDLE' must be initialized by a constant expression

In Windows 10.0.26100.0 INVALID_HANDLE_VALUE define C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\um\handleapi.h as
#define INVALID_HANDLE_VALUE ((HANDLE)(LONG_PTR)-1)

clang interpret "((HANDLE)(.." as reinterpret_cast operation and raise error:

[build]    77 |         constexpr static Handle INVALID_HANDLE = INVALID_HANDLE_VALUE;
[build] /code/src/remote\../remote\../common/ThreadStart.h:77:26: error: constexpr variable 'INVALID_HANDLE' must be initialized by a constant expression
[build]    77 |         constexpr static Handle INVALID_HANDLE = INVALID_HANDLE_VALUE;
[build]       |                                 ^                ~~~~~~~~~~~~~~~~~~~~
[build] /code/src/remote\../remote\../common/ThreadStart.h:77:43: note: cast that performs the conversions of a reinterpret_cast is not allowed in a constant expression
[build]    77 |         constexpr static Handle INVALID_HANDLE = INVALID_HANDLE_VALUE;
[build]       |                                                  ^
[build] C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\um\handleapi.h:27:31: note: expanded from macro 'INVALID_HANDLE_VALUE'
[build]    27 | #define INVALID_HANDLE_VALUE ((HANDLE)(LONG_PTR)-1)
[build]       |                               ^

No excepton in MSVS compiler. Clang has more hard control of a constant expression...

[aafemt]

Why not to return to #define INVALID_HANDLE INVALID_HANDLE_VALUE?

[Khalyutin]

Why not to return to #define INVALID_HANDLE INVALID_HANDLE_VALUE?

We're trying to solve the problem of compiling and building CMake+Clang without changing the approaches adopted in Firebird to avoid things complicating...

[AlexPeshkoff]

Suggest to add a comment why constexpr not used here. Or this change may become cleanup victim.

[Khalyutin]

Suggest to add a comment why constexpr not used here. Or this change may become cleanup victim.

Would this commentary be suitable?

/*
"constexpr" not applicable for Handle INVALID_HANDLE = INVALID_HANDLE_VALUE because in Windows INVALID_HANDLE_VALUE define in handleapi.h as 
"#define INVALID_HANDLE_VALUE ((HANDLE)(LONG_PTR)-1)"
The Clang++ compiler does not consider it`s as a constant and raise compilation error: 
"constexpr variable 'INVALID_HANDLE' must be initialized by a constant expression"
*/

[AlexPeshkoff]

On 6/3/26 20:38, Sergey Khalyutn wrote: *Khalyutin* left a comment (FirebirdSQL/firebird#9049) <#9049 (comment)> Suggest to add a comment why constexpr not used here. Or this change may become cleanup victim. Would this commentary be suitable?

I think should be slightly expanded:

|/* "constexpr" not applicable for Handle INVALID_HANDLE = INVALID_HANDLE_VALUE because in Windows INVALID_HANDLE_VALUE define in handleapi.h as "#define INVALID_HANDLE_VALUE ((HANDLE)(LONG_PTR)-1)"|

but C-cast & reinterpret_cast<>() are prohibited in constexpr

|The Clang++ compiler does not consider it`s as a constant |

expression

…

|and raise compilation error: "constexpr variable 'INVALID_HANDLE' must be initialized by a constant expression" */ |