How can I use the compile time constant __LINE__ in a string?

Question

I can use __LINE__ as a method parameter just fine, but I would like an easy way to use it in a function that uses strings.

For instance say I have this:

Answer 1

There's no reason to do any run-time work for this:

#include <iostream>

// two macros ensures any macro passed will
// be expanded before being stringified
#define STRINGIZE_DETAIL(x) #x
#define STRINGIZE(x) STRINGIZE_DETAIL(x)

// test
void print(const char* pStr)
{
    std::cout << pStr << std::endl;
}

int main(void)
{
    // adjacent strings are concatenated
    print("This is on line #" STRINGIZE(__LINE__) ".");
}

---

Or:

#define STOP_HAMMER_TIME(x) #x
#define STRINGIFICATE(x) STOP_HAMMER_TIME(x)

If you're a cool person like James.

Answer 2

Yes, it's ugly. You need a combination of macros. Converting an integer to a string is a two-step process - here's Boost's implementation:

#define BOOST_STRINGIZE(X) BOOST_DO_STRINGIZE(X)
#define BOOST_DO_STRINGIZE(X) #X

Now you can generate a string:

logError(__FILE__ BOOST_STRINGIZE(__LINE__) "testcondition failed");