Thread: program-wide global variable

i have program split large number of files, , number of them need access path of opened file.

right have file named 'common.hpp' , declare filename.

code:

static std::string log_file = "";

and set in 1 place in program, doesn't set in other areas. did debugging , found every file apparently has own copy of 'log_file'.

understanding of 'static' keyword allocated once when program runs. apparently isn't quite accurate... how without passing string through million functions (ie, how consistent view of 'log_file')? have declare variable 'extern' somewhere?

also, whats wrong view of 'static'?

a static global variable different static variable inside function or static member function/variable.

static global variable or static (non-member) function means object has static linkage, meaning accessible code inside current compilation unit. means it's visibility @ file-level. 'static string log_file', each time header file included in separate file, file got it's own, private variable named 'log_file'.

c-ish way asking. in c++ might consider singleton or other fancy design pattern.

code:

// foo.h #ifndef _foo_h_ #define _foo_h_ #include <string>  // allow other files access our variable const std::string& get_log_file(); #endif

code:

// foo.c #include "foo.h"  // private file static std::string log_file;  const std::string& get_log_file()  {     return log_file; }

code:

// test.c  #include "foo.h"  const std::string& log_file = get_log_file();

alternatively, put following in header file:

code:

extern std::string log_file;

and in single .c file:

code:

std::string log_file;

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