__fltused whats the difference

NTDEV
1

i found out ntstrsafe.lib and libcntpr.lib fix the error LNK2001: unresolved external symbol _fltused whats the difference between those two how they handle __fltused is it true ntstrsafe.lib reduce the buffer overruns?

2

__fltused is nothing more than a flag the compiler adds that signals that your driver uses floating point, to force the C runtime to initialize things. And please note that if you ARE using floating point, you must take special precautions, because the floating point registers are not saved on kernel transitions.

3

im using SSE floating point operations in kernel is it not saved automatically? i know x86 had issues with it

4

SSE is fine in x64 systems. If your driver runs in x86 systems, then you must save and restore the state yourself.

5

i found out to use libcntpr we need also define /D "USE_LIBCNTPR=1" so its use that library then we do for example
#ifdef USE_LIBCNTPR

#include <xmmintrin.h>
#include <wdm.h>

void performFloatingPointOperations() {
__m128 a = _mm_set_ps(1.0f, 2.0f, 3.0f, 4.0f);
__m128 b = _mm_set_ps(4.0f, 3.0f, 2.0f, 1.0f);
__m128 c = _mm_add_ps(a, b);

float results[4];
_mm_store_ps(results, c);
for (int i = 0; i < 4; i++) {
    DbgPrint("Result[%d] = %f\n", i, results[i]);
}

}
#endif