C++ compile time macros to detect windows os - c++

Are there any C++ compile time macros which exists to detect which Windows OS the code is being compiled on. I basically want to support certain functions only on Win7. So I am interested in doing something like this
#if <os_macro> = WIN7
// This function would do something valid only on Win7 builds.
bool myfunction {
// do something here
}
#else
// This function would typically return false, since its not supported on OS below win7
bool myfunction {
return false;
}
#endif
Is there any other better way to do this?

The OS that it's getting compiled on is not all that important; what matters more is the OS that the code is running on, which you obviously cannot detect at compile time. But if you want your code to run on older versions of Windows, you can set WINVER and _WIN32_WINNT to certain values, which will cause newer functions not to be available etc. (just search the Windows header files for where those macros get tested to get an idea).
To test for functionality at runtime, use GetProcAddress (and possibly also LoadLibrary, if it's in a newer DLL) to test if the function is available. If it is, call it, if not, don't.
See also the predefined macros used by the Visual Studio compiler if you want to detect the compiler version etc.

There are a set of standard windows header macros to tell you the exact version of the OS

There are certain things that do require knowing which OS version at compile time.
For example import "winhttp.dll" will compile under Windows 7, but cause compile time error (C1083) under Windows 10.
But if you switch to import "winhttpcom.dll". It would compile under Windows 10 but fail under Windows 7.
So an OS macro is needed here to import appropriate dll.

At least with MS VC++, WIN32, _WIN32, and _WIN32_WINNT, for starters. Unless you need to control it at compile time, you might consider using something like GetVersionEx to detect at run-time, so the same build runs on older versions, but takes advantage of new features when they're available.

My response is 10 yrs late but posting the answer for upcoming yrs.
For detecting the version c/c++ compiler version can be used. Suitable macro is mentioned below:
_MSC_VER
_MSC_FULL_VER
Reference: MS macros

My two cents for people that want to compile / include differently between CONSOLE and WIN32 App under visual Studio (2017) in my case.
You you use wizard to create a Console App, You will have:
WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)
under:
If You use wizard for win32 GUI App:
WIN32;_DEBUG;_WINDOWS;%(PreprocessorDefinitions)
so NO _CONSOLE.
so You can write:
#ifdef _CONSOLE
// for Console
#else
// for GUI
#endif // _CONSOLE
int main()
{
#ifdef _CONSOLE
// for Console
#else
// for GUI
#endif // _CONSOLE
return 0;
}

Related

CLION detecting UNIX operating system on WINDOWS computer

I am trying to write a program that opens up a com port to communicate but works on both LINUX and WINDOWS. To do this, I am using the method outlined in many other sources:
#ifdef __unix__
#linux code
#else
#windows code
#endif
If I copy the code into VSCode, it functions correctly. However, when I do this in CLION, it is detecting the operating system as LINUX instead of WINDOWS and greying out the WINDOWS code. Additionally, when I run the code, it crashes because it is attempting to execute the LINUX based code. This is an example of what I have written:
#ifdef __unix__
int comPort;
struct termios tty;
#else
HANDLE comPort;
char settingString[128];
#endif
And it is executing the unix code. I understand that the comparison happens at compile time, but is there anything I am doing wrong for CLION?
I figured out the issue. My CLION toolchain was default set to WSL and I had to change it to MinGW.
__unix__ defines the Unix environment (available API like POSIX, BSD), not a target OS. You might want to use _WIN32 for detecting Windows environment. Clion probably defines both of them. See more info on Pre-defined C/C++ compiler macros.
#ifndef _WIN32
int comPort;
struct termios tty;
#else
HANDLE comPort;
char settingString[128];
#endif
By the way, #ifdef __unix__ is not detecting Linux, that should be #ifdef __linux__.
CLion does not define any macro, it is the job of the compiler. CLion just get the information from the compiler you have configured in the toolchain section of the settings.
My knowledge of Windows development is very imperfect, but the only compilers I can think which would define __unix__ under Windows are those which are part of a Unix/Posix environment (Cygwin, WSL or some others which are far more confidential). But if you where using them the program should compile -- I presume that what you report as a crash is a failure to compile -- and the result be executable baring other issues; or if the program does compile but fail to execute, that failure should have another source, such as not finding the needed support DLL, than crashing when trying to execute the unixy part of the code.
In other words, you have an installation or configuration issue and your lack of understanding of the context make it difficult to help you as your description of the issue is confusing. There is nothing wrong with you -- everybody has to learn -- but StackOverflow is not a web site designed to provide the kind of hand holding help you need to get unstuck.

Build my application for a previous Windows platform

Background
I'm writing a C++ app using VS2015 on WIN 7. This app will run on all windows OS greater than equal to XP.
Through out my code, I use lots of WINAPI calls.
I wish to prevent, at compile time, the usage of API that are not defined in win XP.
Motivation
At some point, I used function RegDeleteKeyEx function without noticing that this API is NOT available in win XP
Solution
So, I follow this post: Modifying WINVER and _WIN32_WINNT and declared this:
#include <winsdkver.h>
#define _WIN32_WINNT 0x0501
#define WINVER 0x0501
in file targetver.h
I was hoping that after this fix, when I compile my project that contains usage of RegDeleteKeyEx function, I will get compilation error.
But I didn't.
QA
I tried looking for other, new WINAPI in vista, and just added a call to GetTickCount64 function. when compiling, I got this:
error C3861: 'GetTickCount64': identifier not found
which confirmed my solution.
Question
I've noticed that for RegDeleteKeyEx function, the Minimum supported client is Windows Vista, Windows XP Professional x64 Edition
However, my app will run in XP 32 as well.
How may I enforce compilation error in such use case?
Unfortunately, as I can see in "winreg.h", there is no conditional compilation of RegDeleteKeyEx (other than RegDeleteKey). So there is no (easy) way to trigger compilation error in this case.
The only option (for the regular statical DLL loading) would be to create your own wrapper over winreg.h (or windows.h) which would handle the version check (and e.g. #undef RegDeleteKeyEx in the corresponding cases).
Sometimes this kind of stuff is also solved using dynamic DLL loading (LoadLibrary / GetProcAdress) where you can check the presence of the particular function on the current version of Windows, where the application runs (so you could for example create a RegDeleteKey wrapper which would call RegDeleteKeyEx on the windows versions which support it and RegDeleteKey if run under versions which don't). The check of the feature presence is then done at runtime, so the program can run on any version of system and still use the newest features on the versions which support them (and doesn't have DLL "unresolved import" loading issues on the lower versions which do not support the feature).

Tool for determining version of Win32 APIs used by C++ code?

I'm modifying a large C++ project whose first release was Windows 7-only to work on Vista and XP.
The main work will be to change the W7 API calls to use GetProcAddress at runtime (to avoid static linking with methods that are not available on the other platforms), and so I'm wondering if there are any tools that can help identify which calls need to be changed -- hopefully by examining the C++ code itself.
Failing that, would it be best to try building the project against an older Windows SDK? -- for example: http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=6510
#define WINVER 0x501
Now everything that is newer than Windows XP will cause a compilation error.
Replace everything that causes an error until none remain.
If you have some sed-fu, you can probably write a filter that directly finds all #if WINVER > 0x501 blocks in the windows headers, but for me, this is a bit out of my scope :-)
I would open your binaries using the depends.exe tool (either from your VS install or from here) under WinXP and Vista to see which functions can't be statically linked under these OSes. These would be the functions which your binary is using, but which are missing in older releases of the OS. You'll have to deal with them somehow: either implement them by yourself, replace them with something else or disable some of the functionality of your app.

Why _WIN32_WINNT == 0x400 in Qt Creator on Windows 7 machine?

I'm using Qt Creator 2.0.1 based on Qt 4.7.0 (32 bit). The OS is Windows 7 Ultimate (32 bit).
I'd like to restart Windows using the following function call:
ExitWindowsEx(EWX_REBOOT, SHTDN_REASON_MAJOR_SYSTEM |
SHTDN_REASON_MINOR_NETWORK_CONNECTIVITY);
I've added windows.h and reason.h in the source code and added libuser32 in the LIBS section of *.pro file.
After compiling the code, Qt Creator issues an error saying SHTDN_REASON_MAJOR_SYSTEM and SHTDN_REASON_MINOR_NETWORK_CONNECTIVITY are not define in the scope.
I looked into reason.h file that comes with mingw. I found the #defines are inside an #if:
#if (_WIN32_WINNT >= 0x0501)
I looked into the value of _WIN32_WINNT which appears to be 1024 (0x400).
I understand this represents some kind of version number and those #defines should be compiled after a specific version. But why _WIN32_WINNT is so low on Windows 7? How can I use those #defines? I do not want to put direct values instead of SHTDN_REASON_MAJOR_SYSTEM and SHTDN_REASON_MINOR_NETWORK_CONNECTIVITY.
The value of _WIN32_WINNT indicates the version of the Win32 API you're targeting at runtime. It has nothing to do with the version of the OS you happen to be using while doing the build.
If you set this to a higher value before including the API header files more API functions and definitions will become available, but making use of those functions may cause your application to refuse to run on previous versions of Windows. Typically, you want to use the lowest value that you can get away with.
It's safe to use #define values from higher API versions as long as you check for errors from Win32 functions indicating that the value is not supported. Using Win32 functions, however, will cause your application to fail on startup with errors like "DLL import not found".
When you use the Windows SDK, you can specify which versions of Windows your code can run on. The preprocessor macros WINVER and _WIN32_WINNT specify the minimum operating system version your code supports.
When you upgrade an older project, you may need to update your WINVER or _WIN32_WINNT macros. If they're assigned values for an unsupported version of Windows, you may see compilation errors related to these macros.
from:https://learn.microsoft.com/en-us/cpp/porting/modifying-winver-and-win32-winnt?view=vs-2019

Port Mingw32 based code to msvc2008

We recently had a new requirement to use the phonon component of Qt, which on windows requires Visual Studio.
I installed VS2008 and ran a compile. There are a stack of problems due to make not working anything like nmake.
Since I need to maintain cross-platform I want to test which compiler is being used so that I can make changes as required.
An example is that the PRETTY_FUNCTION is a g++ macro with FUNCDNAME being the VC equivalent. How do I test which compiler I am using to determine which macro to call?
Use the _MSC_VER macro. If it is defined, you're using Visual Studio:
#ifdef _MSC_VER
... MSVC code ...
#else
... other compiler ...
#endif