The build process + misc Lecture 3

Compiling / linking (the file extensions are windows, general idea is for all OS’s) When you build a project, there are several sub-steps Pre-processor expansions Compiling Linking Debug-file (pdb) creation When the user runs the executable [in debugger] Dynamic linking OS process creation [Debug Triggers]

Step1: Pre-processor expansion All #xyz sections (in .cpp) are textually replaced // foo.h #define AMT 5.0f #define min(a, b) (a) < (b) ? (a) : (b) void foo(int a, float b); class Test { }; // foo.cpp #include “foo.h” bool foo(int x, float y) { if (x < y) return min(x, AMT); else return min(y, AMT); } Pre-processor // foo.cpp // foo.h void foo(int a, float b); class Test {}; bool foo(int x, float y) { if (x < y) return (x) < (5.0f) ? (x) : (5.0f); else return (y) < (5.0f) ? (y) : (5.0f); }

Step1b: Pre-compiled Headers The process of evaluating headers… especially if a header includes another header …can take a long time. All C/C++ compilers have an option to enable pre-compiled headers All the header evaluations are done once and stored in a massive pch file / database. Anytime a full-rebuild is initiated or a header changes, the pch file is rebuilt. So…we want to include non-changing headers in the pch and do everything else as normal.

step1b, cont. Steps in visual studio (make sure to do this for Debug and Release) ProjectProperties => C/C++ => PreCompiled Headers Precompiled Header => Use (/Yu) Create a stdafx.h and put all non-changing headers in it: #include <string> #include <SDL.h> // etc. Create stdafx.cpp #include <stdafx.h> // (and this is all!) Right-click on stdafx.cpp in Solution Explorer and pick Properties Change C/C++ => PreCompiled Headers => Precompiled Header to Create (/Yc) For every .h and .cpp file you create from here on, include <stdafx.h> as the first thing. Else you’ll get some cryptic error message.

Step2: Compiler Every .cpp (there are no longer .h files!) in the project is converted to machine code (.obj) foo.obj* // foo.cpp // foo.h void foo(int a, float b); class Test {}; bool foo(int x, float y) { if (x < y) return (x) < (5.0f) ? (x) : (5.0f); else return (y) < (5.0f) ? (y) : (5.0f); } LDX INTIM BNE Hold STX WSYNC STX VBLANK STX REFP0 STX REFP1 INX STX VDELP0 STX VDELP1 LDX #$03 STX NUSIZ0 STX NUSIZ1 STX HMCLR NOP ... Compiler * Technically, this is a disassembly of what would look like binary gibberish

Step3: Linker The linker combines… …into a single .exe All machine code in .obj files from our project. All statically-linked .lib files also machine code, but not from our project. e.g. SDL.lib All stubs for dynamically-linked code. These are also .lib files (usually small by comparison) But…they contain code which requests the OS load in a dll at run-time. Any other system-specific code E.g. The c-runtine (or .NET runtime) code …into a single .exe If a debug build, the following database is built in tandem: addresses in the exe and function entry-points addresses in the process for variable locations (stack and heap) [doesn’t actually store the source code!] This is all stored in a .pdb file

Step4: Runtime When the exe is launched: Discussion The OS creates a process and allocates x pages of memory All exe-relative addresses are translated to physical addresses This might happen in the CPU, depending on architecture During startup, the process may request object code to be loaded into the process memory The CPU begins executing machine code in the process And modifying variables stored in process memory Discussion Why are dll’s used in modern OS’s – why not just static lib’s? Licensing restrictions of libs (e.g. LGPL)

Pointer crash-course Several important aspects [examples on board] Pointers to primitives (and addressing) Pointer – array connection (pointer arithmetic) Pointers to structures / objects Pointer and dynamic allocation (arrays and objects)

SDL basics Simple DirectMedia Layer Very c-oriented (can still be “embedded in C++”) Used for: windowing input 2d image support (loading / blitting) sound (2d only) threading (useful before C++11) …(a few other minor things) Should be familiar from ETEC2110 We’ll later render our Ogre stuff to an SDL window. [Look at important parts of wiki together]

doxygen [Have Jason give a demo here…]

The dreaded “style talk” [Show them the thing]