Bitwise AND between c_short and hex value 0x8000 causes range error due to unexpected interpretation of the most-significant bit

[rullo24]

Zig Version

0.14.0-dev.850+ddcb7b1c1

Steps to Reproduce and Observed Behavior

When returning the bitwise AND between a c_short and a hex value, the most-significant bit is considered out-of-range, despite still being within the bounds of a c_short (u16). As seen in the error message below, this is because I presume the 0x8000 is being converted to the i16 equivalent and then being pushed through bitwise operations (-32767 <= i16 <= 32767).

For example (where _getCurrKeyState(virt_key) returns a c_short):

// checking if a key is currently activated
pub fn isPressed(virt_key: VK) bool {
    return ((_getCurrKeyState(virt_key) & 0x8000) != 0); // key pressed (down)
}

Error Message:

PS F:\Coding\01.Projects\06.Zig\01-Zeys\example\zig-out\bin> zig build
install
└─ install key_press
   └─ zig build-exe key_press Debug native 1 errors
F:\Coding\01.Projects\06.Zig\01-Zeys\src\zeys.zig:78:43: error: type 'c_short' cannot represent integer value '32768'
    return ((_getCurrKeyState(virt_key) & 0x8000) != 0); // key pressed (down)
                                          ^~~~~~
referenced by:
    waitUntilKeyPressed: F:\Coding\01.Projects\06.Zig\01-Zeys\src\zeys.zig:71:21
    main: F:\Coding\01.Projects\06.Zig\01-Zeys\example\src\key_press.zig:13:29
    WinStartup: C:\Program Files\zig\lib\std\start.zig:616:37
    comptime_0: C:\Program Files\zig\lib\std\start.zig:65:21
error: the following command failed with 1 compilation errors:
C:\Program Files\zig\zig.exe build-exe -freference-trace=10 -luser32 -ODebug --dep zeys -Mroot=F:\Coding\01.Projects\06.Zig\01-Zeys\example\src\key_press.zig -Mzeys=F:\Coding\01.Projects\06.Zig\01-Zeys\src\zeys.zig --cache-dir F:\Coding\01.Projects\06.Zig\01-Zeys\example\.zig-cache --global-cache-dir C:\Users\conno\AppData\Local\zig --name key_press --zig-lib-dir C:\Program Files\zig\lib\ --listen=-
Build Summary: 2/5 steps succeeded; 1 failed
install transitive failure
└─ install key_press transitive failure
   └─ zig build-exe key_press Debug native 1 errors
error: the following build command failed with exit code 1:
F:\Coding\01.Projects\06.Zig\01-Zeys\example\.zig-cache\o\41affe15a6c2524836c8c2bacba0da2e\build.exe C:\Program Files\zig\zig.exe C:\Program Files\zig\lib F:\Coding\01.Projects\06.Zig\01-Zeys\example F:\Coding\01.Projects\06.Zig\01-Zeys\example\.zig-cache C:\Users\conno\AppData\Local\zig --seed 0x3d38602b -Z355eda3502fcbc06

Expected Behavior

The most-significant bit of a c_short should still be considered within range when bitwise AND operations are taken against it.

[rullo24]

For further context, here is the implementation of the functions that are involved within the example:

// gets the state bitmap of a specified virtual key --> used to check if key as pressed down
fn _getCurrKeyState(virt_key: VK) c_short {
    const virt_key_c_short: c_short = @intFromEnum(virt_key); // converting enum val so that it is usable
    const virt_key_int: c_int = virt_key_c_short; // converting to c_int for ABI compatibility
    const key_state_short: c_short = GetAsyncKeyState(virt_key_int);
    return key_state_short;
}

[dreilly1982]

This is because c_short is an i16, and 0x8000 as a literal is being read as a u16. Try using c_ushort instead of c_short, and see if that works better.

[rohlem]

& currently requires both argument to be of the same type.
If you want the bit sequence that c_ushort uses for the integer value 0x8000 to be interpreted as a c_short,
you can achieve this by casting: @as(c_short, @bitCast( @as(c_ushort, 0x8000) ))

Alternatively you could also reinterpret the other argument as c_ushort: @as(c_ushort, @bitCast(_getCurrKeyState(virt_key))) & 0x8000
or directly return a c_ushort from _getCurrKeyState.
(Or use a more bespoke type, like a packed struct(u16), to address bits individually instead of using bit operations on the values directly.)