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Editorial Team
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Asked: 2026-06-01T18:27:55+00:00

I need to put markers to C++ code that should be visible in assembly

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I need to put markers to C++ code that should be visible in assembly or binary. It seems it’s straight forward to do it for 32 using inline assembly:

__asm {
    NOP
    NOP
    NOP
}

or using DB assembly statement:

__asm {
     DB  0x00, 0xFF, 0x10
}

But VisualStudio 2005 and better does not support inline assembly for x64. Is there any way to do it? Probably I can make a function in separate assembly module but how I can be sure that linker will put an actual assembly there instead of CALL?

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1 Answer

  1. Editorial Team

    Define a global volatile variable somewhere, say volatile __int64 blah = 0;. Then wherever you want some marker, use _InterlockedCompareExchange64(&blah, SOME_UNIQUE_CONSTANT1, SOME_UNIQUE_CONSTANT2);. You’ll be guaranteed to find instructions loading ECX:EBX with SOME_UNIQUE_CONSTANT1 and EDX:EAX with SOME_UNIQUE_CONSTANT2 followed by LOCK CMPXCHG8B (0xF0, 0x0F, 0xC7, etc — see instruction encoding details).

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