In the link below the C++ code's comments it says;
// and compile with -DPSAPI_VERSION=1
https://learn.microsoft.com/en-us/windows/win32/api/psapi/nf-psapi-enumprocessmodules
How do we compile with -DPSAPI_VERSION=1 ?
Two possibilities
just before the include of windows.h add
#define PSAPI_VERSION=1
or in the project properties there is a place to define macros, add PSAPI_VERSION=1 there
Macros are defined in the program. I usually define a macro in the cmake file as a switch. Then in the program, if the macro is found to be defined, the algorithm library call is executed, because my algorithm library is sometimes not configured properly.
CMakeLists.txt
add_definitions(-DRecognitionLIB")
in cpp file
#ifdef RecognitionLib
#include <GBProcess.h>
#include <AIScrapperVision.h>
#endif
function aaa()
{
#ifdef RecognitionLib
some code
#endif
}
Related
I have a MSVC C++ project, I am conditionally compiling parts of the source code by passing specifing Preprocessor Defintions in the C++/Preprocessor section of the Project Properties.
What I would also like to do is conditionally link with libraries based on the preprocessor definitions, how do I achieve this?
For example in my project if CLSOPENLDV is defined I want to exclude:
nodetalk32_vcpp.obj
and include:
ldv32.lib
And when it isn't defined I want to do the opposite.
You probably need this:
#ifdef SOME_MACRO
#pragma comment( lib, "ldv32" )
#endif
This is Microsoft specific, it probably won't work with gcc, clang or other compilers.
For excluding nodetalk32_vcpp.obj the only thing you can do that comes into my mind is:
#ifndef SOME_MACRO
// content of nodetalk32_vcpp.cpp
#endif
I have a C++ code which needs to include a certain library in some servers and not in other servers. I build my code using bjam.
Code example:
if server in server_list:
include <header-file.h>
int function();
else:
int function();
And during build using bjam:
if server in server_list:
-llibrary
else:
...
Header file inclusion is a compile time activity not run time. So you can't use if conditions for the same
use #ifdefs
#define SERVER_IN_LIST
#ifdef SERVER_IN_LIST
#include<...>
#endif
In C and C++ any line that begins with a # is a pre-processor directive. The pre-processor is a text parser that parses a source code file before it is compiled. It understands particular directives such as #include, #define and #ifdef but it treats normal C++ code as if it were text. For this reason, you can't use normal C++ code to alter the interpretation of the pre-processor directives.
Let's look at an example:
if (x == 4){
#include "x4.h"
}
The above is wrong because the if statement and its braces are part of the C++ code so will be ignored by the pre-processor. The pre-processor will go straight ahead and interpret the #include directive, which will cause the contents of x4.h to be pasted into that position in the file.
The correct way to write this is to use conditional pre-processor directives such as #if or #ifdef. For example...
#ifdef INCLUDE_X4
# include "x4.h"
#endif
Note that the indentation in this code is optional.
More information about pre-processor directives can be found here.
I have a package of C functions and I need to create DLL library from it, that can be used in C++ program. I haven't done any library before, so I am total beginner in that. I am working in Qt Creator.
My first try was to create it according to the manual Creating shared libraries, so I added these two lines to my project file:
TEMPLATE = lib
DEFINES += MYLIB_LIBRARY
Then I created mylib.h file
#ifndef MYLIB_H
#define MYLIB_H
#include "mylib_global.h"
#include "functions1.h"
#include "functions2.h"
#include "functions3.h"
class MYLIBSHARED_EXPORT Mylib
{
public:
Mylib(){};
};
#endif // MYLIB_H
Finally I added mylib_global.h:
#ifndef MYLIB_GLOBAL_H
#define MYLIB_GLOBAL_H
#include <QtCore/qglobal.h>
#if defined(MYLIB_LIBRARY)
# define MYLIBSHARED_EXPORT Q_DECL_EXPORT
#else
# define MYLIBSHARED_EXPORT Q_DECL_IMPORT
#endif
#endif // MYLIB_GLOBAL_H
To make functions usable in C++ I used these lines for each function in library
#ifdef __cplusplus
extern "C"{
#endif
void foo();
#ifdef __cplusplus
}
#endif
When compiling with MSVC2012 everything seems ok and I got some .dll file. But then I sent library to someone, who wanted to use it in Borland C++. He told me that I have to compile it with some DEF file to tell to VS compiler right names and with __stdcall instead of __cdecl. But I have no idea how to do it in Qt. Any explanation and help would be really appreciated. Thanks
P.S. I looked at posts Using VS dll in old Borland and Import VS dll in C Builder, but they
did not help me to understand the problem.
If you want to export the foo function, you need to tell the linker somehow.
What you were suggested is to use a .def file, which is quite easy.
Just create a file like exports.def in your project directory, and write in it something like:
EXPORTS
foo
Then go to your library project settings -> Linker -> Input -> Module Definition File
and fill in your .def file name
I am including a third party header and source file into my project.
At the top of the header there is this:
#if defined(WIN32) || defined(WIN16)
#ifndef MSDOS
#define MSDOS
#endif
#endif
#include <stdio.h>
#include <stdlib.h>
#ifndef MSDOS
#include <unistd.h>
#endif
#include "des.h"
The problem is that #if defined(WIN32) fails and the compilation fails when trying to #include unistd.h which I don't want to do.
I have third party project that works with this header file i.e. WIN32 is defined and it doesn't try to include In Visual Studio I did "Go To Definition" on "WIN32" and was taken to the following definition in WinDefs.h.
#define WIN32
I'm not sure this is where its getting WIN32 definition from, as the third party project does not appear to include "WinDefs.h".
So my problem is, how can I get WIN32 to be defined in my current new project?
Depends on your project setup. WIN32 is defined inside the windows header files, but you can pass it to the compiler as well ("-DWIN32" for gcc for example). Try it and see whether it compiles.
Visual Studio has the built-in define _WIN32. mingw-gcc has WIN32 and _WIN32 built-in so the project was likely tested using gcc. You might add
#if defined(_WIN32) && !defined(WIN32)
#define WIN32
#endif
or just add a -DWIN32 to the CFLAGS.
Check your includes. I am guessing that the third party header is included prior to the windows.h. So, in your main.cpp or equal it should be
#include <windows.h> // this will also include windefs.h
#include <thirdParty.h>
and not the other way around.
Hope that helps.
You can simply include the windows header files (windows.h) before including the third party header - as you already found out WIN32 is defined there but technicaly it could be defined anywhere (so if the third party project is not including the windows headers check if it's being defined in the compiler project settins directly).
BTW there is also a _WIN32 define that is set by the compiler, it's possibly a better idea to look for this define if checking if the code is being compiled under windows;
For those seeking answers to the
where is WIN32 defined
part of the questions, I've found it defined in:
minwindef.h
ole2.h
Note, I have no confidence that these are the only places it's defined. I expect there are probably other files where it's defined. Nevertheless, I thought this might help some people.
Some WIN32 defined in the compiler . Just like this，If you use the gcc for windows , WIN32 is defined . If you use the gcc for linux , WIN32 is not defined :)
So , the macros is a switch. You can define it to use somethine , and not define it to unuse something.
I've tried placing the following in my C++ code:
#ifdef _WIN32
#include "stdafx.h"
#endif
but I getan error:
PCH warning: header stop cannot be in a macro of #if block. An IntelliSense PCH file was not generated.
I'm trying to let my code work both on windows and linux, stdafx.h does not work on linux where it's a must on visual studio.
Is there another way to use the include with ifdef?
Unfortunately you can not do that with precompiled header and using Microsoft MSVC. The MSVC totally ignores all code (and whatever garbage) lines that precede that #include "stdafx.h" line. As result the #endif will be unexpected to it.
Put that #ifdef _WIN32 and what not inside of stdafx.h.
I have just created an empty stdafx.h. With follow content for solutions without pre-compiled headers
#pragma once
//this is only for using Common modules with Precompiled headers. We can't disable it using a preprocessor(
//https://stackoverflow.com/a/36271896/6160632