MACRO to concatinate FILE and LINE__ with formatting

Question

I have used macros in following way in my .cpp file named Test.cpp which is present in the location c:\Test\Test.cpp

Inside test.cpp

#define FILE_NAME strrchr(__FILE__, '\\') ? strrchr(__FILE__, '\\') + 1 : __FILE__
#define S1(x) #x
#define S2(x) S1(x)    
#define LOCATION FILE_NAME " : " S2(__LINE__)
//#define LOCATION __FILE__" : " S2(__LINE__) Working but giving the whole file path where as i need only Filename:Line number

Inside Function 
{
  ::MessageBox(NULL,LOCATION,"Test",MB_OK); //Here i am getting only Filename .
}

Please help me in writing a MACRO so that i can get both Filename(Not the full path , only Filename) and Line number in my application .

No , it prints from messagebox line only .

Viku
– Viku

2014-07-22 09:12:01 +00:00
Commented Jul 22, 2014 at 9:12 — Viku
– Viku, Commented Jul 22, 2014 at 9:12

Wojtek Surowka · Accepted Answer · 2014-07-22 09:09:40Z

2

You try to concatenate string literal with the result of strrchr. This is not feasible. You will need a helper function, something like

std::string get_location(const std::string& file, int line)
{
  std::ostringstream ostr;
  size_t bspos = file.find_last_of('\\');
  if (bspos != std::string::npos)
    ostr << file.substr(bspos + 1) << " : " << line;
  else
    ostr << file << " : " << line;
  return ostr.str();
}

#define LOCATION (get_location(__FILE__, __LINE__))

answered Jul 22, 2014 at 9:09

Wojtek Surowka

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5 Comments

Viku Over a year ago

Is there any way to achieve the same through macro only ?

Wojtek Surowka Over a year ago

It should be doable with definiing macro returning std::string and then concatenating using + with colon and the line number. But I do not see any advantage over using a function.

Viku Over a year ago

I tried but unable to do it . Can you please help me in this ?

Wojtek Surowka Over a year ago

Here you go, but this code searches twice for backslash: #define FILE_NAME (strrchr(FILE, '\\') ? std::string(strrchr(FILE, '\\')+1) : std::string(FILE)) #define LOCATION (FILE_NAME + " : " + std::to_string(LINE))

Wojtek Surowka Over a year ago

std::to_string was added in C++11, maybe you use a compiler without C++11 support. Write then your own to_string in similar way as in the code in the answer.

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