Pour obtenir une clé
d'essai remplissez le formulaire ci-dessous
Demandez des tariffs
Nouvelle licence
Renouvellement de licence
--Sélectionnez la devise--
USD
EUR
RUB
* En cliquant sur ce bouton, vous acceptez notre politique de confidentialité

Free PVS-Studio license for Microsoft MVP specialists
To get the licence for your open-source project, please fill out this form
** En cliquant sur ce bouton, vous acceptez notre politique de confidentialité.

I am interested to try it on the platforms:
** En cliquant sur ce bouton, vous acceptez notre politique de confidentialité.

Votre message a été envoyé.

Nous vous répondrons à


Si vous n'avez toujours pas reçu de réponse, vérifiez votre dossier
Spam/Junk et cliquez sur le bouton "Not Spam".
De cette façon, vous ne manquerez la réponse de notre équipe.

>
>
Why is the value of the ProgramFiles en…

Why is the value of the ProgramFiles environment variable replaced with that of ProgramFiles(x86)?

23 Jan 2012
Author:

Why is the value of the %ProgramFiles% environment variable replaced with the value of %ProgramFiles(x86)% when accessing it from a 32-bit program launched in a 64-bit operating system?

When a 32-bit application launched in a 64-bit Windows addresses the system environment variables %ProgramFiles% or %commonprogramfiles%, the WoW64 subsystem replaces the values of these variables with the values of the variables %ProgramFiles(x86)% and "%commonprogramfiles(x86)%. Thus, for instance, %ProgramFiles% will be opened as "C:\Program Files (x86)" when addressing from a 32-bit program.

This behavior is determined by the register redirection system that provides backward compatibility of 32-bit software with 64-bit operating systems. The 32-bit environment is emulated for 32-bit programs even despite the fact that the data they are addressing is located in a different place.

To avoid such a redirection in a 32-bit program, you should use the %programfiles% or %COMMONPROGRAMFILES% (i.e. with reverse case) environment variables or the KEY_WOW64_64KEY flag when accessing the corresponding register nodes.

To completely disable the file system redirection mechanism in the given thread, you may use the functions Wow64DisableWow64FsRedirection / Wow64RevertWow64FsRedirection but using them usually causes issues with implicit calls and delayed library loading. Developers rarely have complete control over the whole input-output process in the area between Wow64DisableWow64FsRedirection and Wow64RevertWow64FsRedirection and if code is implicitly loaded at the moment when the redirection mechanism is disabled, a 32-bit application will most probably fail to get the necessary version of the library. Alexey Pahunov, one of the WoW64 developers, advises to use this pair of functions only to wrap the call of the CreateFile function.

References

Popular related articles
macOS 10.15 no longer supports 32-bit apps. What can you do?

Date: 15 Oct 2019

Author: Sergey Khrenov

On October 7, 2019, Apple released a new version of its Mac operating system, macOS Catalina. Version 10.15 contains many changes and improvements. One of the significant is the complete phasing out …
If the coding bug is banal, it doesn't mean it's not crucial

Date: 19 Avr 2017

Author: Andrey Karpov

Spreading the word about PVS-Studio static analyzer, we usually write articles for programmers. However, some things are seen by programmers quite one-sided. That is why there are project managers wh…
Detecting Overflows of 32-Bit Variables in Long Loops in 64-Bit Programs

Date: 22 Mar 2016

Author: Andrey Karpov

One of the problems that 64-bit software developers have to face is overflows of 32-bit variables in very long loops. PVS-Studio code analyzer is very good at catching issues of this type (see the Vi…
Is it possible to run 64-bit applications in a 32-bit OS?

Date: 08 Déc 2015

Author: Andrey Karpov

Nowadays 64-bit operating systems are very widespread. But 32-bit OS are still present on the market, in quite obvious quantities. A lot of modern program tools are developed to be run only in 64-bit…
How to Port a 9 Million Code Line Project to 64 bits?

Date: 03 Aoû 2015

Author: Evgeniy Ryzhkov, Ilya Ivanov

Our team has recently finished porting one pretty large project (9 million code lines, 300 Mbytes of source files) to the 64-bit platform. It took us one year and a half. Although we are not permitte…

Comments (0)

Next comments
Unicorn with delicious cookie
Nous utilisons des cookies pour améliorer votre expérience de navigation. En savoir plus
Accepter