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[SPCA] Fix various errors

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Janis Hutz
2026-01-23 10:33:49 +01:00
parent b86fd00a60
commit 25b3381294
15 changed files with 36 additions and 23 deletions
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6
semester3/spca/parts/01_c/01_basics/07_pointers.tex
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@@ -4,7 +4,7 @@ On loading of a program, the OS creates the virtual address space for the proces
before other preparations like final linking and relocation are done.
Stack-based languages (supporting recursion) allocate stack in frames that contain local variables, return information and temporary space.
When a procedure is entered, a stack frame is allocated and executes any necessary setup code (like moving the stack pointer, see later). % TODO: Link to correct section
When a procedure is entered, a stack frame is allocated and executes any necessary setup code (like moving the stack pointer, see \ref{sec:asm-stack}).
When a procedure returns, the stack frame is deallocated and any necessary cleanup code is executed, before execution of the previous frame continues.
\bi{In \lC\ a pointer is a variable whose value is the memory address of another variable}
@@ -19,13 +19,15 @@ The (Linux)-Kernel randomizes the address space to prevent some common exploits.
\end{scriptsize}
\content{Pointer Arithmetic} Note that when doing pointer arithmetic, adding $1$ will move the pointer by \texttt{sizeof(type)} bits.
Pointer arithmetic with a \texttt{void} pointer is thus not allowed by standard \lC, as the compiler does not know the size of the data type.
However, \texttt{gcc} does allow it and assumes the size of \texttt{void} is \texttt{1 byte}.
You may use pointer arithmetic on whatever pointer you'd like (as long as it's not a null pointer).
This means, you \textit{can} make an array wherever in memory you'd like.
The issue is just that you are likely to overwrite something, and that something might be something critical (like a stack pointer),
thus you will get \bi{undefined} behaviour! (This is by the way a common concept in \lC, if something isn't easy to make more flexible
(example for \texttt{malloc}, if you pass a pointer to memory that is not the start of the \texttt{malloc}'d section, you get undefined behaviour),
in the docs mention that one gets undefined behaviour if you do not do as it says so\dots RTFM!)
in the docs mention that one gets undefined behaviour if you do not do as it says, so\dots RTFM!)
As already seen in the section arrays (section \ref{sec:c-arrays}), we can use pointer arithmetic for accessing array elements.
The array name is treated as a pointer to the first element of the array, except when: