In your current example there is no difference: On variable declarations, constexpr implies const, and a const variable at namespace scope has internal linkage by default (so adding static does not change anything). In C++14, you cannot declare a variable as constexpr and have it have external linkage unless you only ever do this in … Read more
Language linkage is the term used for linkage between C++ and non-C++ code fragments. Typically, in a C++ program, all function names, function types and even variable names have the default C++ language linkage. A C++ object code can be linked to another object code which is produced using some other source language (like C) … Read more
First I’d like to clarify my understanding of the situation you describe: The header contains (only) a static function declaration while the C file contains the definition, i.e. the function’s source code. For example some.h: static void f(); // potentially more declarations some.c: #include “some.h” static void f() { printf(“Hello world\n”); } // more code, … Read more
I hope that you’re not asking about the main entries, which are stating that for the requested library libm.so.6 it was found in the file /lib/libm.so.6, for example, but are asking about the two outliers. Why are they displayed differently? for linux-gate.so.1 it’s because it’s not actually a file on-disk – it’s exposed by the … Read more
The purpose of the preprocessor statements: #ifdef _GUICTRLS #define GUI_CTRLS_EXPORT __declspec(dllexport) #else #define GUI_CTRLS_EXPORT __declspec(dllimport) #endif is to make sure that the header file declares the class or function as __declspec(dllexport) in the .dll where it is defined, and as __declspec(dllimport) for any other .dll that might want to use it. For this to work, … Read more
Most C compilers provide an option for this, such as the -o option for gcc and some others: gcc -o gentext gentext.c cc -o mainprog -Llib -lmymath firstbit.c secondbit.o xlc -o coredump coredump.c
C and C++ are superficially similar, but each compiles into a very different set of code. When you include a header file with a C++ compiler, the compiler is expecting C++ code. If, however, it is a C header, then the compiler expects the data contained in the header file to be compiled to a … Read more
extern “C” makes a function-name in C++ have C linkage (compiler does not mangle the name) so that client C code can link to (use) your function using a C compatible header file that contains just the declaration of your function. Your function definition is contained in a binary format (that was compiled by your … Read more