Windows Compilation Fails: CMake errors in setup_env and missing `const` in ggml-bitnet-mad

[Lakshay-Singh]

Bug Description:
When attempting to compile BitNet from source on a standard Windows environment, the build fails in two separate places:

###Bug 1: CMake Generator Failure in setup_env .py
The compiler script passes the -T ClangCL argument to CMake on Windows. However, it does not explicitly specify a Generator (like -G "Visual Studio 17 2022"). On many Windows systems, CMake will default to the NMake Makefiles generator, which immediately crashes because NMake does not support the -T toolset flag.

Error log:
Generator NMake Makefiles does not support toolset specification, but toolset ClangCL was specified.

The Fix for Bug 1:
In setup_env .py (Line 72), explicitly define the Visual Studio Generator so CMake can actually use the ClangCL toolset.
Change from:
OS_EXTRA_ARGS = {
"Windows":["-T", "ClangCL"],
}

Change to:
OS_EXTRA_ARGS = {
"Windows":["-G", "Visual Studio 17 2022", "-T", "ClangCL"],
}

---

Bug 2: Missing const type-cast in ggml-bitnet-mad .cpp

Once CMake successfully generates the build files using ClangCL, the actual C++ compilation crashes. The strict Windows Clang compiler rejects an assignment on line 811 inside the AVX2 block of src/ggml-bitnet-mad .cpp because a const modifier was forgotten.

Error log:
error : cannot initialize a variable of type 'int8_t *' with an rvalue of type 'const int8_t *'

The Fix for Bug 2:
In src/ggml-bitnet-mad .cpp (Line 811), the pointer y is explicitly declared as a constant on line 794, so y_col must also be a constant.

Change from:
int8_t * y_col = y + col * by;

Change to:
const int8_t * y_col = y + col * by;

With these two tiny fixes applied, the system compiles flawlessly out-of-the-box on Windows using AVX2 and Clang!