Chapter 01: Towards Modern C++

Before learning modern C++, let’s take a look at the main features that have been deprecated since C++11:

The string literal constant is no longer allowed to be assigned to a char *. If you need to assign and initialize a char * with a string literal constant, you should use const char * or auto.
```
  char *str = "hello world!"; // A deprecation warning will appear
```
C++98 exception description, unexpected_handler, set_unexpected() and other related features are deprecated and should use noexcept.
auto_ptr is deprecated and unique_ptr should be used.
register keyword is deprecated and can be used but no longer has any practical meaning.
The ++ operation of the bool type is deprecated.
C language style type conversion is deprecated (ie using (convert_type)) before variables, and static_cast, reinterpret_cast, should be used for type conversion.
In particular, some of the C standard libraries that can be used are deprecated in the latest C++17 standard, such as <ccomplex>, <cstdalign>, <cstdbool> and <ctgmath> Wait
… and many more

There are also other features such as parameter binding (C++11 provides std::bind and std::function), export, and etc. are also deprecated. These features mentioned above If you have never used or heard of it, please don’t try to understand them. You should move closer to the new standard and learn new features directly. After all, technology is moving forward.

For some force majeure and historical reasons, we had to use some C code (even old C code) in C++, for example, Linux system calls. Before the advent of modern C++, most people talked about “what is the difference between C and C++”. Generally speaking, in addition to answering the object-oriented class features and the template features of generic programming, there is no other opinion, or even a direct answer. “Almost” is also a lot of people. The Wayne diagram in Figure 1.2 roughly answers the C and C++ related compatibility.

From now on, you should have the idea that “C++ is not a superset of C” in your mind (and not from the beginning, later [References for further reading] (# further reading references) The difference between C++98 and C99 is given). When writing C++, you should also avoid using program styles such as void* whenever possible. When you have to use C, you should pay attention to the use of extern "C", separate the C language code from the C++ code, and then unify the link, for instance:

gcc -c foo.c

Comple and output the foo.o file, and link the C++ code to the .o file using clang++ (or both compile to .o and then unlink them together):

Of course, you can use Makefile to compile the above code:

C = gcc
SOURCE_C = foo.c
OBJECTS_C = foo.o
TARGET = 1.1
LDFLAGS_COMMON = -std=c++2a
all:
    $(C) -c $(SOURCE_C)
    $(CXX) $(SOURCE_CXX) $(OBJECTS_C) $(LDFLAGS_COMMON) -o $(TARGET)
clean:
    rm -rf *.o $(TARGET)

Note: Indentation in Makefile is a tab instead of a space character. If you copy this code directly into your editor, the tab may be automatically replaced. Please ensure the indentation in the Makefile. It is done by tabs.

If you don’t know the use of Makefile, it doesn’t matter. In this tutorial, you won’t build code that is written too complicated. You can also read this book by simply using on the command line.

If you are new to modern C++, you probably still don’t understand the following small piece of code above, namely:

Don’t worry at the moment, we will come to meet them in our later chapters.

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