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[SPCA] Fixes a few errors

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Janis Hutz
2026-01-25 08:11:16 +01:00
parent eb6240c26e
commit 0770c76ef3
11 changed files with 30 additions and 11 deletions
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semester3/spca/parts/01_c/02_preprocessor.tex
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@@ -4,13 +4,20 @@ To have \texttt{gcc} stop compiliation after running through \texttt{cpp}, the \
\content{Imports} Imports in \lC\ are handled by the preprocessor, that for each \verb|#include <file1.h>|, the preprocessor simply copies the contents of the file recursively into one file. Note that this can easily lead to errors caused by multiple definitions. Using the \texttt{cpp} directive \verb|#ifndef| can be used to avoid this.
Depending on if we use \verb|#include <file1.h>| or \verb|#include "file1.h"| the preprocessor will search for the file either in the system headers or in the project directory.
Depending on if we use \verb|#include <file1.h>| or \verb|#include "file1.h"| the preprocessor will search for the file either in the system headers
(on Linux typically in \texttt{/usr/include/}) or in the project directory.
Be wary of including files twice, as the preprocessor will recursively include all files (i.e. it will include files from the files we included)
It is however possible to prevent that from becoming an issue using this (called an \texttt{include guard}):
\inputcodewithfilename{c}{}{code-examples/00_c/01_preprocessor/00_include-guards.h}
The name you pick for the preprocessor macro used in the check, by convention usually has the form \texttt{NAME\_H}.
It should not start in an underscore (or multiple) and it should not contain more than one consecutive underscore.
The \lC\ preprocessor gives us what are called \texttt{preprocessor macros}, which have the format \verb|#define NAME SUBSTITUTION|.
\rmvspace
\inputcodewithfilename{c}{}{code-examples/00_c/01_preprocessor/00_macros.c}
\inputcodewithfilename{c}{}{code-examples/00_c/01_preprocessor/01_macros.c}
To avoid issues with semicolons at the end of preprocessor macros that wrap statements that cannot end in semicolons, we can use a concept called semicolon swallowing.
For that, we wrap the statements in a \texttt{do \dots\ while(0)} loop, which is removed by the compiler on compile, also taking with it the semicolon.