summaryrefslogtreecommitdiff
path: root/a6
diff options
context:
space:
mode:
authorBent Bisballe Nyeng <deva@aasimon.org>2023-08-04 21:30:35 +0200
committerBent Bisballe Nyeng <deva@aasimon.org>2023-08-04 21:30:35 +0200
commitb4e8a41aca5a22fc02da3b1a29ca10e4d472b6c7 (patch)
tree2cfab980424343c0daed8ea342f416e437fc0bfc /a6
parent345480d2c0647a1a4bf8b7915d78155a261ea988 (diff)
A6: WIP
Diffstat (limited to 'a6')
-rw-r--r--a6/Makefile15
-rw-r--r--a6/au_BentBisballeNyeng_A6.tex154
-rw-r--r--a6/exercise.tex50
-rw-r--r--a6/fragmentation.svg321
-rw-r--r--a6/noalloc.cc68
-rw-r--r--a6/references.bib44
6 files changed, 602 insertions, 50 deletions
diff --git a/a6/Makefile b/a6/Makefile
new file mode 100644
index 0000000..61ea860
--- /dev/null
+++ b/a6/Makefile
@@ -0,0 +1,15 @@
+all: noalloc pdf
+
+noalloc: noalloc.cc Makefile
+ g++ -g -O0 -Wall -Werror -Wextra -Wconversion -std=c++20 $< -o $@
+
+pdf: au_BentBisballeNyeng_A6.pdf
+au_BentBisballeNyeng_A6.bbl: au_BentBisballeNyeng_A6.bcf
+ biber $<
+
+au_BentBisballeNyeng_A6.bcf: au_BentBisballeNyeng_A6.tex
+ xelatex -halt-on-error $<
+
+au_BentBisballeNyeng_A6.pdf: au_BentBisballeNyeng_A6.tex au_BentBisballeNyeng_A6.bbl
+ xelatex -halt-on-error $<
+ xelatex -halt-on-error $<
diff --git a/a6/au_BentBisballeNyeng_A6.tex b/a6/au_BentBisballeNyeng_A6.tex
new file mode 100644
index 0000000..ad4cc0d
--- /dev/null
+++ b/a6/au_BentBisballeNyeng_A6.tex
@@ -0,0 +1,154 @@
+\title{Essay: Applying Contemporary C++ in Enviroments Without
+Free-Store}
+\documentclass[11pt]{article}
+\usepackage{graphicx}
+%\usepackage{xcolor}
+\usepackage{fancyhdr}
+\usepackage{listings}
+\usepackage{subfig}
+\usepackage{biblatex}
+\addbibresource{references.bib}
+\renewcommand{\floatpagefraction}{.8}%
+%\renewcommand{\thesubfigure}{Figure \arabic{subfigure}}
+\captionsetup[subfigure]{labelformat=simple, labelsep=colon}
+\pagestyle{fancy}
+\author{Bent Bisballe Nyeng <deva@aasimon.org> University of Aarhus}
+\begin{document}
+\maketitle
+
+\begin{abstract}
+%\section*{Abstract}
+
+In this essay I want to examine to which extend it is possible to use
+free-store allocating constructs from the standard template library
+(STL) and C++ core-language in enviroments without access to a
+free-store.
+\end{abstract}
+
+\section{Introduction}
+C++ contains a lot of helpful constructs that can be widely used,
+including in environments without a free-store, such
+as \texttt{concepts}, \texttt{module}s, \texttt{template}s in general,
+and functions from \texttt{algorithm} in particular but some parts of
+the language and the STL is off-limits when building applications in
+environments without free-store such as the perhaps obvious, but
+useful \texttt{std::vector} or \texttt{std::string}, but also the less
+obvious co-routines\cite{belson} or storing lambdas
+in \texttt{std::function}s\cite{elbeno}.
+This also inherently means that RAII cannot be used for managing memory
+allocations (such as smart-pointers), but can still be used for
+managing other types of resources, such as locks or hardware
+peripheral access.
+
+\subsection{Dynamic Memory Allocation}
+
+There can be many reasons for not allocating on the free-store, either
+by convention; ``no allocations allowed after the engines has
+started'', or because the hardware or operating system doesn't
+have a virtual memory abstraction, ie. doesn't have a memory
+management unit (MMU)\cite{tannenbaum}, and therefore, over time, is
+at risk at fragmenting the memory available ultimately leading to
+memory depletion\cite{weis}.
+
+In the case of memory fragmentation one might argue that it is not the
+allocation that is the problem but rather the free'ing since this is
+when the fragmentation happens. This problem is shown in
+figure \ref{frag}, which might be possible to circumvent in singular
+concrete cases, but cannot be solved in general without the page
+indirections of the virtual memory\cite{weis}.
+
+\begin{figure}
+\makebox[\textwidth][c]{%
+\includegraphics[scale=0.8]{fragmentation.pdf}}
+\caption{\textit{(a) visualizes the full, free, memory of a system.
+Then, in (b), 4 equal-sized chunks of memory has been allocated
+filling up the whole memory. In (c) chunk 2 and 4 has been free'd and
+finally, in (d), a chunk which can fit in the total amount of
+free memory, is being allocated but fails because of memory
+fragmentation.}}
+\label{frag}
+\end{figure}
+
+This can to some degree be prevented by monotonic allocations which
+might work for not very practical in real-world
+software and certainly not for the dynamic allocations in the STL or
+the core-language.
+
+In particular, a lambda stored in a \texttt{std::function} might
+allocate memory on the free-store if the lambda exceeds the size of
+the (compiler dependent) small-buffer optimization (SBO) buffer inside
+the \texttt{std::functions}\cite{elbeno}. In much the same way as
+the \texttt{std::string} has its small string optimization (also
+compiler dependent).
+
+\subsection{Free-Standing}
+
+Work is being done to modify the ``free-standing C++'' towards, among
+other things, making it run on systems without free-store by isolating
+the parts of the STL that can be used entirely without allocating
+along with not supporting exceptions and run-time type
+information\cite{craig}.
+
+Working with the resulting small sub-set of the available components,
+however, is not well suited for making contemporary C++ applications.
+The ideal solution would be to find ways to be able to use all (or at
+least most) features, but with a potential known set of restictions or
+limitations.
+
+\section{Method}
+In the following, 3 methods for managing memory allocations will be
+investigated, and their suitability for real-life applications be
+evaluated:
+\begin{itemize}
+\item Using Custom Allocators for the STL components that supports it.
+\item Overloading \texttt{new}/\texttt{delete} to use stack allocated
+ memory instead of the free-store for all allocation.
+\item Support from the compiler to fail compilation if an
+ unintentional \texttt{new} or \texttt{delete} is being called,
+ at least preventing accidental allocations.
+\end{itemize}
+
+Each of the three will be evaluated with large lambda
+captures, \texttt{std::vector} allocation and some simple co-routines.
+The epxeriments are done on a linux PC using the gcc-11.2 compiler.
+
+\section{Experiments}
+
+
+----------------------------------------
+
+
+No access to MMU, implicitly, prohibits calls to delete after
+initialization phase. Otherwise this will lead to memory fragmentation
+which again might lead to free-store depletion and ultimately
+application failure.
+
+Writing a custom allocator is only a solution to a sub-set of the
+allocations in an application, for example if all allocations are
+guaranteed to always be of the same size, in which can no
+fragmentation will occur.
+
+But for most applications (or at least most parts on an application)
+this is not the case, and therefore others means need to be taken into
+use.
+
+The most common way of addressing this, is simply to only use stack
+allocation, or store all objects in as static globals.
+But in certain areas of the C++ language dynamic allocation might
+occur without the developer knowing about it.
+\texttt{std::string}s of sizes that doesn't fit in the SSO buffer is
+one example, but even more devious is the capture clause of a
+lambda, which might allocate extra memory, if more than $N$ members
+are captured, where $N$ is compiler dependent.
+
+No way of telling the compiler that ``no allocations allowed, fail if
+one is made'' exists, but one could wish for such a mechanism in the
+wake of the ``free-standing C++'' subset work.
+One thing is to prohibit use of language constructs that are
+guaranteed to allocate, but quite another is to allow using constructs
+in ways that doesn't make them allocate.
+This, I think, is not part of the ``free-standing C++'' work.
+
+\printbibliography
+
+\end{document}
diff --git a/a6/exercise.tex b/a6/exercise.tex
deleted file mode 100644
index 2cdace6..0000000
--- a/a6/exercise.tex
+++ /dev/null
@@ -1,50 +0,0 @@
-\title{Essay: Applying contemporary C++ in applications for embedded
-microcontrollers.}
-\documentclass[11pt]{article}
-\usepackage{graphicx}
-%\usepackage{xcolor}
-\usepackage{fancyhdr}
-\usepackage{listings}
-\usepackage{subfig}
-\renewcommand{\floatpagefraction}{.8}%
-%\renewcommand{\thesubfigure}{Figure \arabic{subfigure}}
-\captionsetup[subfigure]{labelformat=simple, labelsep=colon}
-\pagestyle{fancy}
-\author{Bent Bisballe Nyeng <deva@aasimon.org> University of Aarhus}
-\begin{document}
-\maketitle
-
-No access to MMU, implicitly, prohibits calls to delete after
-initialization phase. Otherwise this will lead to memory fragmentation
-which again might lead to free-store depletion and ultimately
-application failure.
-
-Writing a custom allocator is only a solution to a sub-set of the
-allocations in an application, for example if all allocations are
-guaranteed to always be of the same size, in which can no
-fragmentation will occur.
-
-But for most applications (or at least most parts on an application)
-this is not the case, and therefore others means need to be taken into
-use.
-
-The most common way of addressing this, is simply to only use stack
-allocation, or store all objects in as static globals.
-But in certain areas of the C++ language dynamic allocation might
-occur without the developer knowing about it.
-\texttt{std::string}s of sizes that doesn't fit in the SSO buffer is
-one example, but even more devious is the capture clause of a
-lambda, which might allocate extra memory, if more than $N$ members
-are captured, where $N$ is compiler dependent.
-
-No way of telling the compiler that ``no allocations allowed, fail if
-one is made'' exists, but one could wish for such a mechanism in the
-wake of the ``free-standing C++'' subset work.
-One thing is to prohibit use of language constructs that are
-guaranteed to allocate, but quite another is to allow using constructs
-in ways that doesn't make them allocate.
-This, I think, is not part of the ``free-standing C++'' work.
-
-
-
-\end{document}
diff --git a/a6/fragmentation.svg b/a6/fragmentation.svg
new file mode 100644
index 0000000..4aa629d
--- /dev/null
+++ b/a6/fragmentation.svg
@@ -0,0 +1,321 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+ width="107.47267mm"
+ height="42.140366mm"
+ viewBox="0 0 107.47267 42.140366"
+ version="1.1"
+ id="svg5"
+ inkscape:version="1.1 (c68e22c387, 2021-05-23)"
+ sodipodi:docname="fragmentation.svg"
+ xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+ xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+ xmlns="http://www.w3.org/2000/svg"
+ xmlns:svg="http://www.w3.org/2000/svg">
+ <sodipodi:namedview
+ id="namedview7"
+ pagecolor="#ffffff"
+ bordercolor="#666666"
+ borderopacity="1.0"
+ inkscape:pageshadow="2"
+ inkscape:pageopacity="0.0"
+ inkscape:pagecheckerboard="0"
+ inkscape:document-units="mm"
+ showgrid="false"
+ showguides="true"
+ inkscape:guide-bbox="true"
+ inkscape:zoom="2.3162177"
+ inkscape:cx="276.74428"
+ inkscape:cy="-10.36172"
+ inkscape:window-width="2560"
+ inkscape:window-height="1381"
+ inkscape:window-x="0"
+ inkscape:window-y="30"
+ inkscape:window-maximized="1"
+ inkscape:current-layer="layer1"
+ fit-margin-top="0"
+ fit-margin-left="0"
+ fit-margin-right="0"
+ fit-margin-bottom="0" />
+ <defs
+ id="defs2">
+ <marker
+ style="overflow:visible"
+ id="Arrow1Lend"
+ refX="0"
+ refY="0"
+ orient="auto"
+ inkscape:stockid="Arrow1Lend"
+ inkscape:isstock="true">
+ <path
+ transform="matrix(-0.8,0,0,-0.8,-10,0)"
+ style="fill:context-stroke;fill-rule:evenodd;stroke:context-stroke;stroke-width:1pt"
+ d="M 0,0 5,-5 -12.5,0 5,5 Z"
+ id="path45096" />
+ </marker>
+ </defs>
+ <g
+ inkscape:label="Layer 1"
+ inkscape:groupmode="layer"
+ id="layer1"
+ transform="translate(-7.7885291,-21.702475)">
+ <g
+ id="g45802"
+ transform="translate(-0.30718184,0.18621279)">
+ <rect
+ style="fill:#0000ff;fill-opacity:1;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870"
+ width="24.729277"
+ height="4.6249619"
+ x="16.584129"
+ y="31.165308" />
+ <rect
+ style="fill:#0000ff;fill-opacity:1;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-3"
+ width="24.729277"
+ height="4.6249619"
+ x="41.313408"
+ y="31.165304" />
+ <rect
+ style="fill:#0000ff;fill-opacity:1;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-6"
+ width="24.729277"
+ height="4.6249619"
+ x="66.042686"
+ y="31.165304" />
+ <rect
+ style="fill:#0000ff;fill-opacity:1;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-7"
+ width="24.729277"
+ height="4.6249619"
+ x="90.771965"
+ y="31.165306" />
+ </g>
+ <g
+ id="g45809"
+ transform="translate(0.0295179)">
+ <g
+ id="g1084-7"
+ transform="translate(-0.15966059,-18.796201)">
+ <rect
+ style="fill:#ffffff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-5-0"
+ width="24.729277"
+ height="4.6249619"
+ x="16.407091"
+ y="40.565823" />
+ <rect
+ style="fill:#ffffff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-3-3-93"
+ width="24.729277"
+ height="4.6249619"
+ x="41.136368"
+ y="40.565819" />
+ <rect
+ style="fill:#ffffff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-6-5-6"
+ width="24.729277"
+ height="4.6249619"
+ x="65.865639"
+ y="40.565819" />
+ <rect
+ style="fill:#ffffff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-7-6-0"
+ width="24.729277"
+ height="4.6249619"
+ x="90.594925"
+ y="40.565819" />
+ </g>
+ </g>
+ <text
+ xml:space="preserve"
+ style="font-style:normal;font-weight:normal;font-size:3.88056px;line-height:125%;font-family:sans-serif;letter-spacing:0px;word-spacing:0px;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+ x="7.5041366"
+ y="25.025614"
+ id="text3467"><tspan
+ sodipodi:role="line"
+ id="tspan3465"
+ style="font-style:italic;font-variant:normal;font-weight:500;font-stretch:normal;font-size:3.88056px;font-family:'Adobe Times';-inkscape-font-specification:'Adobe Times Medium Italic';stroke-width:0.264583px"
+ x="7.5041366"
+ y="25.025614">(a)</tspan></text>
+ <text
+ xml:space="preserve"
+ style="font-style:normal;font-weight:normal;font-size:3.88056px;line-height:125%;font-family:sans-serif;letter-spacing:0px;word-spacing:0px;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+ x="7.82723"
+ y="34.607513"
+ id="text3467-3"><tspan
+ sodipodi:role="line"
+ id="tspan3465-6"
+ style="font-style:italic;font-variant:normal;font-weight:500;font-stretch:normal;font-size:3.88056px;font-family:'Adobe Times';-inkscape-font-specification:'Adobe Times Medium Italic';stroke-width:0.264583px"
+ x="7.82723"
+ y="34.607513">(b)</tspan></text>
+ <text
+ xml:space="preserve"
+ style="font-style:normal;font-weight:normal;font-size:3.88056px;line-height:125%;font-family:sans-serif;letter-spacing:0px;word-spacing:0px;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+ x="7.8272295"
+ y="44.189407"
+ id="text3467-7"><tspan
+ sodipodi:role="line"
+ id="tspan3465-5"
+ style="font-style:italic;font-variant:normal;font-weight:500;font-stretch:normal;font-size:3.88056px;font-family:'Adobe Times';-inkscape-font-specification:'Adobe Times Medium Italic';stroke-width:0.264583px"
+ x="7.8272295"
+ y="44.189407">(c)</tspan></text>
+ <text
+ xml:space="preserve"
+ style="font-style:normal;font-weight:normal;font-size:3.88056px;line-height:125%;font-family:sans-serif;letter-spacing:0px;word-spacing:0px;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+ x="7.82723"
+ y="53.771313"
+ id="text3467-35"><tspan
+ sodipodi:role="line"
+ id="tspan3465-62"
+ style="font-style:italic;font-variant:normal;font-weight:500;font-stretch:normal;font-size:3.88056px;font-family:'Adobe Times';-inkscape-font-specification:'Adobe Times Medium Italic';stroke-width:0.264583px"
+ x="7.82723"
+ y="53.771313">(d)</tspan></text>
+ <g
+ id="g45790"
+ transform="translate(0.30718231)">
+ <rect
+ style="fill:#0000ff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-5-2"
+ width="24.729277"
+ height="4.6249619"
+ x="15.969766"
+ y="50.51532" />
+ <rect
+ style="fill:#ffffff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-3-3-9"
+ width="24.729277"
+ height="4.6249619"
+ x="40.699043"
+ y="50.515316" />
+ <rect
+ style="fill:#0000ff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-7-6-2-2"
+ width="24.729277"
+ height="4.6249619"
+ x="53.647087"
+ y="59.150738" />
+ <rect
+ style="fill:#0000ff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-6-5-1"
+ width="24.729277"
+ height="4.6249619"
+ x="65.428314"
+ y="50.515316" />
+ <rect
+ style="fill:#ffffff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-7-6-2"
+ width="24.729277"
+ height="4.6249619"
+ x="90.1576"
+ y="50.515316" />
+ <rect
+ style="fill:#0000ff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-7-6-2-6"
+ width="24.729277"
+ height="4.6249619"
+ x="78.376366"
+ y="59.150738" />
+ <path
+ style="fill:none;fill-rule:evenodd;stroke:#ff0000;stroke-width:0.16865px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;marker-end:url(#Arrow1Lend)"
+ d="M 90.154475,58.983348 103.24136,55.364262"
+ id="path45009"
+ sodipodi:nodetypes="cc" />
+ <path
+ style="fill:none;fill-rule:evenodd;stroke:#ff0000;stroke-width:0.168916;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1;marker-end:url(#Arrow1Lend)"
+ d="M 66.361775,59.077445 53.352422,55.171509"
+ id="path45011"
+ sodipodi:nodetypes="cc" />
+ </g>
+ <g
+ id="g886"
+ transform="translate(-0.13014269,0.36759303)">
+ <rect
+ style="fill:#0000ff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-5"
+ width="24.729277"
+ height="4.6249619"
+ x="16.407091"
+ y="40.565823" />
+ <rect
+ style="fill:#ffffff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-3-3"
+ width="24.729277"
+ height="4.6249619"
+ x="41.136368"
+ y="40.565819" />
+ <rect
+ style="fill:#0000ff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-6-5"
+ width="24.729277"
+ height="4.6249619"
+ x="65.865639"
+ y="40.565819" />
+ <rect
+ style="fill:#ffffff;stroke:#000000;stroke-width:0.134284;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:1.2"
+ id="rect870-7-6"
+ width="24.729277"
+ height="4.6249619"
+ x="90.594925"
+ y="40.565819" />
+ <g
+ id="g46373"
+ transform="matrix(0.67625997,0,0,0.67625997,17.169551,13.920236)"
+ style="stroke:#ff0000">
+ <g
+ id="g46367"
+ transform="translate(-1.4278149,0.07627992)"
+ style="stroke:#ff0000">
+ <path
+ style="fill:none;fill-rule:evenodd;stroke:#ff0000;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+ d="m 60.513749,41.351531 -12.365481,2.91289"
+ id="path45982"
+ sodipodi:nodetypes="cc" />
+ </g>
+ <g
+ id="g46364"
+ transform="translate(-1.4278149,0.07627992)"
+ style="stroke:#ff0000">
+ <path
+ style="fill:none;fill-rule:evenodd;stroke:#ff0000;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+ d="m 48.148268,41.351531 12.365481,2.91289"
+ id="path45984"
+ sodipodi:nodetypes="cc" />
+ </g>
+ </g>
+ <g
+ id="g46373-0"
+ transform="matrix(0.67625997,0,0,0.67625997,67.368394,14.019017)"
+ style="stroke:#ff0000">
+ <g
+ id="g46367-6"
+ transform="translate(-1.4278149,0.07627992)"
+ style="stroke:#ff0000">
+ <path
+ style="fill:none;fill-rule:evenodd;stroke:#ff0000;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+ d="m 60.513749,41.351531 -12.365481,2.91289"
+ id="path45982-8"
+ sodipodi:nodetypes="cc" />
+ </g>
+ <g
+ id="g46364-7"
+ transform="translate(-1.4278149,0.07627992)"
+ style="stroke:#ff0000">
+ <path
+ style="fill:none;fill-rule:evenodd;stroke:#ff0000;stroke-width:0.264583px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+ d="m 48.148268,41.351531 12.365481,2.91289"
+ id="path45984-9"
+ sodipodi:nodetypes="cc" />
+ </g>
+ </g>
+ </g>
+ <rect
+ style="fill:#0000ff;stroke:#0000ff;stroke-width:0.260804;stroke-dashoffset:4.53543"
+ id="rect19776"
+ width="1.5205654"
+ height="4.2247181"
+ x="77.875946"
+ y="59.347862" />
+ </g>
+</svg>
diff --git a/a6/noalloc.cc b/a6/noalloc.cc
new file mode 100644
index 0000000..0da4025
--- /dev/null
+++ b/a6/noalloc.cc
@@ -0,0 +1,68 @@
+#include <iostream>
+#include <functional>
+
+// Universal allocator
+namespace memory
+{
+void* ptr{};
+}
+
+void* operator new([[maybe_unused]]std::size_t n) // throw(std::bad_alloc) - don't throw
+{
+ std::cout << "new\n";
+ // Just return the supplied stack pointer
+ return memory::ptr;
+}
+
+void operator delete(void*) throw()
+{
+ std::cout << "delete\n";
+ // Do nothing. actual memory is allocated on the stack
+}
+
+void operator delete(void*, std::size_t) throw()
+{
+ std::cout << "delete[]\n";
+ // Do nothing. actual memory is allocated on the stack
+}
+
+//void foo() __attribute__((noinline))
+int main()
+{
+ char buf[256];
+ memory::ptr = buf;
+
+ std::cout << " ** strings:\n";
+ { // strings
+ // now this is ok:
+ std::string str(32, 'a');
+ std::cout << str << '\n';
+
+ std::string str2(24, 'b');
+ std::cout << str << '\n'; // the contents of str has been overwritten
+
+ // this will also allocate, but supply the same buffer - ok
+ str = "hello world hello world hello world";
+
+ // this is also ok, but due to SSO
+ std::string sso{"hello"};
+ }
+
+ std::cout << " ** lambdas:\n";
+ { // lambdas
+ std::function<int()> f;
+ {
+ char foo[16]{};
+ f = [=]()__attribute__((noinline)) // capture up 16 bytes - ok
+ {
+ int i = 0;
+ for(auto v : foo)
+ {
+ i += v;
+ }
+ return i;
+ }; // capture foo by copy - inlined
+ }
+ [[maybe_unused]]auto x = f();
+ }
+}
diff --git a/a6/references.bib b/a6/references.bib
new file mode 100644
index 0000000..5e0e27a
--- /dev/null
+++ b/a6/references.bib
@@ -0,0 +1,44 @@
+@book{tannenbaum,
+ added-at = {2011-05-03T00:00:00.000+0200},
+ author = {Tanenbaum, Andrew S.},
+ biburl = {https://www.bibsonomy.org/bibtex/2e90b050159c1629022a54a2bf947f318/dblp},
+ interhash = {c97d1fa1663502cf42aaf310cc07056f},
+ intrahash = {e90b050159c1629022a54a2bf947f318},
+ isbn = {978-0-13-852872-0},
+ keywords = {dblp},
+ pages = {I-XVII, 1-587},
+ publisher = {Prentice Hall},
+ timestamp = {2011-05-04T11:32:41.000+0200},
+ title = {Structured computer organization, 3rd Edition.},
+ year = 1990
+}
+
+@article{belson,
+ author = {Belson, Bruce and Xiang, Wei and Holdsworth, Jason and Philippa, Bronson},
+ year = {2020},
+ month = {02},
+ pages = {1-1},
+ title = {C++20 Coroutines on Microcontrollers -What We Learned},
+ volume = {PP},
+ journal = {IEEE Embedded Systems Letters},
+ doi = {10.1109/LES.2020.2973397}
+}
+
+@website{elbeno,
+ author = {Ben Deane},
+ title = {Why is a raven like a writing desk? Another myth, about C++ lambdas},
+ url = {https://www.elbeno.com/blog/?p=1068}
+}
+
+@website{weis,
+ author = {Andreas Weis},
+ title = {Taming dynamic memory - Andreas Weis - Meeting C++ 2018},
+ url = {https://github.com/ComicSansMS/presentations/releases/download/meetingcpp2018/taming_dynamic_memory.pdf},
+% url = {https://www.youtube.com/watch?v=R3cBbvIFqFk}
+}
+
+@website{craig,
+ author = {Ben Craig},
+ title = {P2268R0 - Freestanding Roadmap},
+ url = {https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2268r0.html}
+} \ No newline at end of file