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POUnderstanding C++ Compilation
 

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  1. POUnderstanding C++ Compilation
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    <p>I have recently become aware that I have no idea, genericly speaking, how a c/c++ compiler works. I will admit this initialy came from trying to understand header guards but came to the realization that I am lacking in how compiling works.</p> <p>Take Visual C++ for instance; Theres the "Header Files" folder, the "Resources Files" folder, and "Source Files" folder. Is there any significance to the separation of these folders and what you put in them? To me, they are all source files. Take the code snippets:</p> <h1>Snippet 1</h1> <pre><code>//a1.h int r=4; </code></pre> <p>and </p> <pre><code>//a1.cpp int b //&lt;--semicolon left out on purpose </code></pre> <p>and</p> <pre><code>//main.cpp #include &lt;iostream&gt; #include "a1.h" void main() { cout &lt;&lt; r; } </code></pre> <p>The compiler errors out saying "a1.cpp(3) : fatal error C1004: unexpected end-of-file found" where I would expect it wouldn't because the a1.cpp file is not #included where the main method exists where in the next code snippet</p> <h1>Snippet 2</h1> <pre><code>//a1.h int r=4 //&lt;--semicolon left out on purpose </code></pre> <p>and </p> <pre><code>//a1.cpp int b = 4; </code></pre> <p>and</p> <pre><code>//main.cpp #include &lt;iostream&gt; void main() { cout &lt;&lt; b; } </code></pre> <p>Errors out because "main.cpp(6) : error C2065: 'b' : undeclared identifier". If you include the a1.cpp like so</p> <h1>Snippet 3</h1> <pre><code>//a1.h int r=4 //&lt;--semicolon left out on purpose </code></pre> <p>and </p> <pre><code>//a1.cpp int b = 4; </code></pre> <p>and</p> <pre><code>//main.cpp #include &lt;iostream&gt; #include "a1.cpp" void main() { cout &lt;&lt; b; } </code></pre> <p>the compiler complains "a1.obj : error LNK2005: "int b" (?b@@3HA) already defined in main.obj". Both snippets 2 and 3 ignore the fact that <code>int r = 4</code> does not have a semicolon missing as I suspect that it has something to do with its a xxxx.h file. If I remove the a1.cpp file from the project on snippet 1, then it compiles fine. Clearly what I have expected is not what I am getting. Theres plenty of books and tutorials on how to code in cpp, but not much in the way cpp handles files and source code in the complition process. What on earth is going on here?</p>
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    1. COYou need some very basic understanding of the difference between header files and source files, plus the meaning of "project" (or Makefile). Could you start with reading K&R book? It's not C++, but neither is your code - it's plain C (except << stuff).
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    2. COI always recommend that people new to C/C++ use a command line compiler and manually link code before moving into an IDE. Understanding the compilation/linking/execution process is very important in C/C++. Sit back, relax, and GCC a while.
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    3. CO@Brandon Do you mean in a linux/unix environment? Or would is there a windows port? Also, what kind of literature would I want to look at?
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