It’s a preprocessor macro. All of it is preprocessor syntax, that basically says, if this macro has not already been defined, define it and include all code between the #ifndef and #endif What it accomplishes is preventing the inclusion of file more than once, which can lead to problems in your code. Your question: And … Read more
If you are using a GNU compiler, the compiler can assemble a list of dependencies for you. Makefile fragment: depend: .depend .depend: $(SRCS) rm -f “$@” $(CC) $(CFLAGS) -MM $^ -MF “$@” include .depend or depend: .depend .depend: $(SRCS) rm -f “$@” $(CC) $(CFLAGS) -MM $^ > “$@” include .depend where SRCS is a variable … Read more
conio.h is a C header file used with old MS-DOS compilers to create text user interfaces. Compilers that target other operating systems, such as Linux-based, 32-bit Windows and OS/2, provide equivalent functionality through other header files and libraries. The #include <curses.h> will give you almost all of the functionality provided by conio.h. “ncurses” needs to … Read more
Header files (.h) are designed to provide the information that will be needed in multiple files. Things like class declarations, function prototypes, and enumerations typically go in header files. In a word, “definitions”. Code files (.cpp) are designed to provide the implementation information that only needs to be known in one file. In general, function … Read more
To the best of my knowledge, the C++ standard knows no difference between header files and source files. As far as the language is concerned, any text file with legal code is the same as any other. However, although not illegal, including source files into your program will pretty much eliminate any advantages you would’ve … Read more
FIRST QUESTION: Why aren’t include guards protecting my header files from mutual, recursive inclusion? They are. What they are not helping with is dependencies between the definitions of data structures in mutually-including headers. To see what this means, let’s start with a basic scenario and see why include guards do help with mutual inclusions. Suppose … Read more
You should definitely NOT use using namespace in headers for precisely the reason you say, that it can unexpectedly change the meaning of code in any other files that include that header. There’s no way to undo a using namespace which is another reason it’s so dangerous. I typically just use grep or the like … Read more
C++ compilation A compilation in C++ is done in 2 major phases: The first is the compilation of “source” text files into binary “object” files: The CPP file is the compiled file and is compiled without any knowledge about the other CPP files (or even libraries), unless fed to it through raw declaration or header … Read more
What is the difference between #include and #include “filename”?
Initially, just focusing on the Makefile problem: Objects depend on source files… on all the source (and headers) files that are read during the compilation… Unless you’re doing code generation, there’s no makefile dependency among the source/headers used to produce one particular object. For example, you have foo.cpp. foo.cpp will produce foo.o So your target … Read more