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The latest version of this topic can be found at __writeeflags.

Writes the specified value to the program status and control (EFLAGS) register.

void __writeeflags(unsigned Value);  
void __writeeflags(unsigned __int64 Value);  


[in] ValueThe value to write to the EFLAGS register. The Value parameter is 32 bits long for a 32-bit platform and 64 bits long for a 64-bit platform.

These routines are available only as intrinsics.

__writeeflagsx86, x64

Header file <intrin.h>

Compiler Intrinsics