Answer: To use math functions (for example, sqrt or pow) with PSoC Creator, do the following steps: Click Project. Click Build Settings. Open the Linker settings under ARM GCC 4.7.3 and click General. Under Additional Libraries, add m.
An explanation of what is happening:When you define a class you indicate what variables will be in it.When you then instantiate the class ( MyClass c;) the variables within the newly instantiated object get allocated.Static variables never get instantiated. After all - which instance of the class should instantiate them when you create one? And if you never create one? So it's simple: static variables never get created by the class definition or anything else. It is up to you to provide the storage space for that variable, which means statically allocating it in your C code as has been demonstrated.
For standard C programs the entry point is 'main'. For Windows GUI (non-console) programs the entry point is winmain. I forget what the '@16' part is for.You need to describe what you did better. What type of project did you create?
If you did not create a project in VS then are you using the command-line to build the project? If so then what commands are you using?Probably you are trying to compile a GUI properly but you don't have a. Also see.I suggest using VS to create a sample Windows GUI program. From 'File' 'New' 'Project.' Create a new C desktop application as in:Then in the wizard choose 'Windows Application (.exe)' as in the following:Then build and test that. That is a quick way to get sample code.Sam HobbsSimpleSamples.Info. I started learning the windows API for c to build GUI for windows.
To learn a bit more effectively, I decided to copy and build the program and then understand it well. But when I copied the very first empty window program from module 1 of the documentationand built it in vs code using the command gcc filename.h it showed an error ofundefined reference to winmain@16.I don't know what it is or how to resolve it. Searched all over the internet but didn't find an apt answer.
Help me!As Sam Hobbs has indicated in the above post WinMain is the entry pont for a Windows application. I suggest you read the documentation in the links provided in his post. The '@16' following WinMain is the number of bytes in the function'sparameter list for the stdcall convention. See for further information.I also recommend that you install Visual Studio 2017 Community and use the Visual Studio IDE during the learning process.
It is a fully featured environment for coding, buildingand debugging Windows applications and is integrated with the Windows SDK (Software Development Kit) which contains many necessary headers, libraries and helpful tools. It also contains many helpful project templates that simplify the process ofcreating a new application as illustrated in the images that Sam has posted.Work from within the IDE instead of using the command line. This will provide many advantages, including helpful tips while coding from IntelliSense. Using Visual Studio also provides the added benefit of simplifying the learning process by removingthe complexity of properly installing and configuring non-Microsoft development tools. While such tools can be used to develop Windows applications I believe that, for a beginner, using Visual Studio and its IDE is a better path to follow.
Youcan always follow a different path later, when your knowledge and skills have improved. I remember gcc being more picky about the definition of WinMain compared to VC.The WinMain function must be compiled using the stdcall calling convention, but if you look at tutorials and such a lot of them don't include the calling convention, and they still build. It is also looking for a C name mangling instead of C.VC treats main, wmain, WinMain and wWinMain as special, it explicitly looks out for these and makes sure that they are built with the correct calling convention. So if you have the default calling convention as cdecl and c name mangling and definethe function as int WinMain(HINSTANCE, HINSTANCE, LPSTR, int);then VC will silently switch it to the correct calling convention and name mangling type. Extern 'C'int WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int);If the inverse is true and you have a calling convention other than cdecl as the default, then the compiler will look out for main and silently change the calling convention to cdecl.I don't think gcc does this.
So if you haven't already, try explicitly setting your application to use stdcall for WinMain and set the function to extern 'C' and see if this builds.This is a signature. Any samples given are not meant to have error checking or show best practices. They are meant to just illustrate a point. I may also give inefficient code or introduce some problems to discourage copy/paste coding. This is because themajor point of my posts is to aid in the learning process. I started learning the windows API for c to build GUI for windows. To learn a bit more effectively, I decided to copy and build the program and then understand it well.
But when I copied the very first empty window program from module 1 of the documentationand built it in vs code using the command gcc filename.h it showed an error ofundefined reference to winmain@16.You don;t appear to have told us which version of Visual Studio you're using. using the command gcc filename.hNote that you don't normally compile a header file by itself. Headersdon't usually have a main function, so can rarely if ever be used tocreate a complete program and generate an.exe file.Some details on using different compilers - including GCC - with VisualStudio 2017 may be found here: Use any C Compiler with Visual Studio- Wayne. Note that you don't normally compile a header file by itself.I should add an exception to that statement.
You can and may sometimeswant to compile a header to see if there are any compilation errorsin it. However, in such cases you want to do.just. a compile, nota full build which usually includes linking after compilation(s).It is the link step which will generate an error such as 'undefinedreference to winmain@16'. If you just want to compile without linkingthen you need to specify that when you do the build.
Undefined Reference To Function
For GCC you woulduse the -c option, for cl.exe you would use the /c option, etc.From the IDE you can right-click on a source file and choose Compile.- Wayne.