问题
Do compilers offer the capability to automatically check if each source file (and its associated header file, if any) include all other headers that are required? Or at least issue a warning, say, if a required header is not included explicitly?
For example, I would like the compiler to report when I do something like this:
header1.h
#include <string>
...
header2.h
#include "header1.h"
#include <iostream>
std::string blah; //<-- issue warning here, <string> not included explicitly
...
source2.cpp
#include "header2.h"
...
cout << endl; //<-- issue warning here, <iostream> not included explicitly
I am using g++ and Visual Studio, so my question primarily applies to these compilers. Thanks!
回答1:
There is no automatic way for doing so, as far as I know.
My suggestion is to confine inclusions into headers only to what is needed for the "interface" defined in the .h In C++ Coding Standards (Sutter, Alexandrescu) you can find an item which tackles this explicitly (it's titled Make header files self-sufficient). I cite:
Behave responsibly: Ensure that each header you write is compilable standalone, by having it include any headers its contents depend upon
and
But don't include headers that you don't need; they just create stray dependencies. Consider this technique to help enforce header self-sufficiency: In your build, compile each header in isolation and validate that there are no errors or warnings.
Moreover you should always include your own .h first, since this maximizes the probability of finding out if there are inclusion errors.
In all cases, headers should be swappable, so that if your file includes a.h and b.h, both possible orders should do.
来源：https://stackoverflow.com/questions/17569023/checking-header-file-for-dependencies-at-compile-time