To get a trial key
fill out the form below
Team License (a basic version)
Enterprise License (extended version)
* By clicking this button you agree to our Privacy Policy statement

Request our prices
New License
License Renewal
--Select currency--
* By clicking this button you agree to our Privacy Policy statement

Free PVS-Studio license for Microsoft MVP specialists
* By clicking this button you agree to our Privacy Policy statement

To get the licence for your open-source project, please fill out this form
* By clicking this button you agree to our Privacy Policy statement

I am interested to try it on the platforms:
* By clicking this button you agree to our Privacy Policy statement

Message submitted.

Your message has been sent. We will email you at

If you haven't received our response, please do the following:
check your Spam/Junk folder and click the "Not Spam" button for our message.
This way, you won't miss messages from our team in the future.

A common error occurring when compiling…

A common error occurring when compiling a 64-bit application: error C4235, Assembler

Oct 30 2010

Visual C++ does not support 64-bit inline assembler.

That is why you get an error when trying to compile a code like this:

void waitvrt(void)
  __asm {
      mov  dx,3dah
      in    al,dx
      test  al,8
      jnz    VRT
      in    al,dx
      test  al,8
      jz    NoVRT
1>.\Third_party\Src\CreditsThread.cpp(111) :
error C4235: nonstandard extension used :
'__asm' keyword not supported on this architecture

If you still need to use assembler code, you may use a third-party 64-bit assembler, for example, MASM.

But you will most likely need to rewrite the existing code in C/C++. The assembler code is likely to be obsolete and it is more reasonable to use modern functions provided by operating systems or C/C++ constructs. Using assembler for the purpose of optimization can rarely be justified because Visual C++ compiler creates rather efficient code in most cases. Also, remember that you may use intrinsic-functions.

Intrinsic-functions are special system-dependent functions performing such actions that cannot be performed at the level of C/C++ code or that do it much more efficiently than other means. On the whole, they allow you to get rid of inline-assembler because it is often undesirable or impossible to use it.

Programs can use intrinsic-functions to create faster code because there are no expenses on calling common functions. Of course, the size of the code will be a bit larger. MSDN gives the list of the functions that can be replaced with their intrinsic-versions. For example, these are memcpy, strcmp, etc.

Microsoft Visual C++ compiler has a special option "/Oi" that allows you to replace the calls of some functions with their intrinsic-versions automatically.

Besides automatic replacement of common functions with intrinsic-versions, you may use intrinsic-functions in the code explicitly. This is why it may be useful:

  • As I have already said, inline assembler is not supported by Visual C++ in the 64-bit mode. But intrinsic-code is.
  • Intrinsic-functions are simpler to use because you do not need to know registers or other similar low-level constructs when dealing with them.
  • Intrinsic-functions are updated in compilers. But assembler code must be updated manually.
  • The embedded optimizer does not work with assembler code, so you need external linking of the module. But this all does not concern intrinsic-code.
  • Intrinsic-code is easier to port than assembler code.

Using intrinsic-functions in automated mode (with the help of the compiler switch) allows you to get some per cent of performance gain at no cost, and "manual" introduction of intrinsic-functions allows you to get even more. That is why using them is absolutely justified.

To learn more about intrinsic-functions see the Visual C++ team blog.

Popular related articles
The way static analyzers fight against false positives, and why they do it

Date: Mar 20 2017

Author: Andrey Karpov

In my previous article I wrote that I don't like the approach of evaluating the efficiency of static analyzers with the help of synthetic tests. In that article, I give the example of a code fragment…
Free PVS-Studio for those who develops open source projects

Date: Dec 22 2018

Author: Andrey Karpov

On the New 2019 year's eve, a PVS-Studio team decided to make a nice gift for all contributors of open-source projects hosted on GitHub, GitLab or Bitbucket. They are given free usage of PVS-Studio s…
The Ultimate Question of Programming, Refactoring, and Everything

Date: Apr 14 2016

Author: Andrey Karpov

Yes, you've guessed correctly - the answer is "42". In this article you will find 42 recommendations about coding in C++ that can help a programmer avoid a lot of errors, save time and effort. The au…
PVS-Studio ROI

Date: Jan 30 2019

Author: Andrey Karpov

Occasionally, we're asked a question, what monetary value the company will receive from using PVS-Studio. We decided to draw up a response in the form of an article and provide tables, which will sho…
Static analysis as part of the development process in Unreal Engine

Date: Jun 27 2017

Author: Andrey Karpov

Unreal Engine continues to develop as new code is added and previously written code is changed. What is the inevitable consequence of ongoing development in a project? The emergence of new bugs in th…
The Evil within the Comparison Functions

Date: May 19 2017

Author: Andrey Karpov

Perhaps, readers remember my article titled "Last line effect". It describes a pattern I've once noticed: in most cases programmers make an error in the last line of similar text blocks. Now I want t…
How PVS-Studio Proved to Be More Attentive Than Three and a Half Programmers

Date: Oct 22 2018

Author: Andrey Karpov

Just like other static analyzers, PVS-Studio often produces false positives. What you are about to read is a short story where I'll tell you how PVS-Studio proved, just one more time, to be more atte…
The Last Line Effect

Date: May 31 2014

Author: Andrey Karpov

I have studied many errors caused by the use of the Copy-Paste method, and can assure you that programmers most often tend to make mistakes in the last fragment of a homogeneous code block. I have ne…
PVS-Studio for Java

Date: Jan 17 2019

Author: Andrey Karpov

In the seventh version of the PVS-Studio static analyzer, we added support of the Java language. It's time for a brief story of how we've started making support of the Java language, how far we've co…
Appreciate Static Code Analysis!

Date: Oct 16 2017

Author: Andrey Karpov

I am really astonished by the capabilities of static code analysis even though I am one of the developers of PVS-Studio analyzer myself. The tool surprised me the other day as it turned out to be sma…

Comments (0)

Next comments
This website uses cookies and other technology to provide you a more personalized experience. By continuing the view of our web-pages you accept the terms of using these files. If you don't want your personal data to be processed, please, leave this site.
Learn More →