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diff --git a/content/blog/2018-11-28-cpp-compiler.md b/content/blog/2018-11-28-cpp-compiler.md deleted file mode 100644 index a7dce40..0000000 --- a/content/blog/2018-11-28-cpp-compiler.md +++ /dev/null @@ -1,136 +0,0 @@ -+++ -date = 2018-11-28 -title = "The C++ Compiler" -description = "" -draft = false -+++ - -# A Brief Introduction - -[C++](https://en.wikipedia.org/wiki/C%2B%2B) is a general-purpose programming -language with object-oriented, generic, and functional features in addition to -facilities for low-level memory manipulation. - -The source code, shown in the snippet below, must be compiled before it can be -executed. There are many steps and intricacies to the compilation process, and -this post was a personal exercise to learn and remember as much information as I -can. - -```cpp -#include <iostream> - -int main() -{ - std::cout << "Hello, world!\n"; -} -``` - -## Compilation Process - -### An Overview - -Compiling C++ projects is a frustrating task most days. Seemingly nonexistent -errors keeping your program from successfully compiling can be annoying -(especially since you know you wrote it perfectly the first time, right?). - -I'm learning more and more about C++ these days and decided to write this -concept down so that I can cement it even further in my own head. However, C++ -is not the only compiled language. Check out [the Wikipedia entry for compiled -languages](https://en.wikipedia.org/wiki/Compiled_language) for more examples of -compiled languages. - -I'll start with a wonderful, graphical way to conceptualize the C++ compiler. -View [The C++ Compilation -Process](https://web.archive.org/web/20190419035048/http://faculty.cs.niu.edu/~mcmahon/CS241/Notes/compile.html) -by Kurt MacMahon, an NIU professor, to see the graphic and an explanation. The -goal of the compilation process is to take the C++ code and produce a shared -library, dynamic library, or an executable file. - -## Compilation Phases - -Let's break down the compilation process. There are four major steps to -compiling C++ code. - -### Step 1 - -The first step is to expand the source code file to meet all dependencies. The -C++ preprocessor includes the code from all the header files, such as `#include -<iostream>`. Now, what does that mean? The previous example includes the -`iostream` header. This tells the computer that you want to use the `iostream` -standard library, which contains classes and functions written in the core -language. This specific header allows you to manipulate input/output streams. -After all this, you'll end up which a temporary file that contains the expanded -source code. - -In the example of the C++ code above, the `iostream` class would be included in -the expanded code. - -### Step 2 - -After the code is expanded, the compiler comes into play. The compiler takes the -C++ code and converts this code into the assembly language, understood by the -platform. You can see this in action if you head over to the [GodBolt Compiler -Explorer](https://godbolt.org), which shows C++ being converted into assembly -dynamically. - -For example, the `Hello, world!` code snippet above compiles into the following -assembly code: - -```asm -.LC0: - .string "Hello, world!\n" -main: - push rbp - mov rbp, rsp - mov esi, OFFSET FLAT:.LC0 - mov edi, OFFSET FLAT:_ZSt4cout - call std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*) - mov eax, 0 - pop rbp - ret -__static_initialization_and_destruction_0(int, int): - push rbp - mov rbp, rsp - sub rsp, 16 - mov DWORD PTR [rbp-4], edi - mov DWORD PTR [rbp-8], esi - cmp DWORD PTR [rbp-4], 1 - jne .L5 - cmp DWORD PTR [rbp-8], 65535 - jne .L5 - mov edi, OFFSET FLAT:_ZStL8__ioinit - call std::ios_base::Init::Init() [complete object constructor] - mov edx, OFFSET FLAT:__dso_handle - mov esi, OFFSET FLAT:_ZStL8__ioinit - mov edi, OFFSET FLAT:_ZNSt8ios_base4InitD1Ev - call __cxa_atexit -.L5: - nop - leave - ret -_GLOBAL__sub_I_main: - push rbp - mov rbp, rsp - mov esi, 65535 - mov edi, 1 - call __static_initialization_and_destruction_0(int, int) - pop rbp - ret -``` - -### Step 3 - -Third, the assembly code generated by the compiler is assembled into the object -code for the platform. Essentially, this is when the compiler takes the assembly -code and assembles it into machine code in a binary format. After researching -this online, I figured out that a lot of compilers will allow you to stop -compilation at this step. This would be useful for compiling each source code -file separately. This saves time later if a single file changes; only that file -needs to be recompiled. - -### Step 4 - -Finally, the object code file generated by the assembler is linked together with -the object code files for any library functions used to produce a shared -library, dynamic library, or an executable file. It replaces all references to -undefined symbols with the correct addresses. |