How use _emit in clang?

Question

How to use _emit to emit bytes in clang compiler?

e.g(in MSVC):

#define emit_nop() _asm _emit 0x90

clang does not support `_emit` (at least not that I know about it). You can use the `asm` keyword for a similar effect, but I wonder what you are trying to achieve. — fuz, Apr 10 '19 at 17:56

score 1 · Accepted Answer · answered Apr 10 '19 at 18:07

1

In compilers that support GNU extensions, there's no need for a separate emit keyword, just use GNU C inline assembly:

asm(".byte 0x90");   // implicitly   asm volatile

Or .long to emit a 32-bit constant.

GNU C inline asm is not parsed to detect clobbers or anything, so you could just asm("nop");

If you want to use instructions that modify registers, you normally need to tell the compiler about it with GNU C Extended inline assembly (output/input/clobbers). See https://stackoverflow.com/tags/inline-assembly/info.

answered Apr 10 '19 at 18:07

Peter Cordes

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Thank you for the answer, that's exactly what I needed. – cYeR Apr 10 '19 at 18:14
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@cYeR While it's the answer to your question, there is a good chance you're asking the wrong question and it's not what you needed. – Ross Ridge Apr 10 '19 at 18:43

How use _emit in clang?

1 Answers1