CODEWITHSUNDEEP
c++
Lim
Lim

Reputation: 190

C++ Code that runs immediately when the program is turned on

struct First{
    First(){
        printf("first");
    }
}First;

int main()
{
    print("second");
    return 0;
}

I know I can control the code that is executed first through the structure.
So I want to use the following code to make it simple through macro.

#define FIRST_INVOKE(NAME,FUNCTION) \
struct NAME  \
{ \
    NAME() \
    { \
        FUNCTION(); \
    } \
} NAME;
namespace Foo
{
    namespace Bar
    {
        void FirstFunction()
        {
            LOGD(LVID, "First");
        }
    }
}
FIRST_INVOKE(UniqueStructName, Foo::Bar::FirstFunction);

When creating a macro, you must specify the name of the structure. (UniqueStructName)
I want to set this to a name that does not overlap globally automatically.

Namespace and class static functions cannot be included in structure names because :: is required.

Please let me know if there is a good way (I am using Xcode.)

Upvotes: 0

Views: 140

Answers (1)

Morris Franken
Morris Franken

Reputation: 2555

You can automatically generate names based on the line number and use anonymous namespace to avoid multiple definitions across files. E.g, using the following macro:

#define CONCAT_(A,B) A##B
#define CONCAT(A,B) CONCAT_(A,B)
#define NONAME() CONCAT(noname_, __LINE__)
#define FIRST_INVOKE(FUNCTION) \
namespace {                          \
    struct NONAME() \
    { \
        NONAME()() \
        { \
            FUNCTION(); \
        } \
    } NONAME();                      \
}

This will expand to a noname_X struct, where X is the line-number. This works as long as you do not repeat the macro on the same line.

Upvotes: 1

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