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+#+date:2018-11-28
+#+title: The C++ Compiler
+
+* A Brief Introduction
+
+[[https://en.wikipedia.org/wiki/C%2B%2B][C++]] 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.
+
+#+BEGIN_SRC cpp
+#include <iostream>
+
+int main()
+{
+    std::cout << "Hello, world!\n";
+}
+#+END_SRC
+
+* 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 [[https://en.wikipedia.org/wiki/Compiled_language][the Wikipedia entry for compiled
+languages]] for more examples of compiled languages.
+
+I'll start with a wonderful, graphical way to conceptualize the C++ compiler.
+View [[https://web.archive.org/web/20190419035048/http://faculty.cs.niu.edu/~mcmahon/CS241/Notes/compile.html][The C++ Compilation Process]] 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 [[https://godbolt.org][GodBolt Compiler
+Explorer]], which shows C++ being converted into assembly dynamically.
+
+For example, the =Hello, world!= code snippet above compiles into the following
+assembly code:
+
+#+BEGIN_SRC 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
+#+END_SRC
+
+*** 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.