The paper
https://www.usenix.org/legacy/publications/library/proceedings/sa92/spencer.pdf
sounds like it is worth reading.

There are Valgrind tools that can automatically detect many memory management and threading bugs, and profile your programs in detail. You can also use Valgrind to build new tools.

Detailed description of the stack layout, use of R5 as frame pointer by the (V6) Unix C compiler on the pdp-11.

The Amsterdam Compiler Kit is a cross-platform compiler and toolchain suite that is small, portable, extremely fast, and extremely flexible. It targets a number of low-end machines including the Z80, 8086 and 80386, but there are many other code generators available. It supports several languages, including ANSI C, Pascal and Modula-2, and contains integrated runtime libraries including a libc.

The maintainer, David Given states "I, dtrg, cannot honestly recommend using the ACK for production code unless as a stop-gap measure or unless the other benefits of the ACK (e.g. having a very lightweight turnkey toolchain is valuable to you) outweigh the code quality."

Interesting software, such as
unifdef selectively removes C preprocessor conditionals. My version of this program now shipped by all the BSDs (including Mac OS X) and is used by the Linux kernel build system.
regpg safely stores server secrets using gpg, so you can keep them in version control.
picoro - tiny coroutine implementations in pure C. I wrote an accompanying article, coroutines in 20 lines of standard C.
Counting the days - tiny routines for converting Gregorian dates into linear counts, like Julian day numbers or Unix time_t. The date of the count - a small routine for converting linear day counts into Gregorian dates.
https://dotat.at/@/2016-04-22-synergy-vs-xmodmap-fight.html Why you can't use xmodmap to change how Synergy handles modifier keys
https://dotat.at/@/2023-05-26-whence-time.html Where does my computer get the time from?
https://dotat.at/@/2023-08-04-unix69.html a neat keyboard map
https://dotat.at/@/2024-01-29-four-point-egg.html construct an egg shape with straightedge and compass
His log of links, https://dotat.at/:/ which I found on the TUHS mailing list is also worth reading. He explains a bit about this log on http://dotat.at/.

Blog about Unix, C, system administration and more. See for example
https://utcc.utoronto.ca/~cks/space/blog/sysadmin/NotificationsVersusLogs
https://utcc.utoronto.ca/~cks/space/blog/sysadmin/IdentifyMachineEmailByRootName
https://utcc.utoronto.ca/~cks/space/blog/sysadmin/ProceduresAreNotDocumentation
https://utcc.utoronto.ca/~cks/space/blog/sysadmin/RCStoMercurial  Instructions for converting files/directories controlled with RCS to Mercurial.
TODO: mention M-x vc-revision-other-window. Saved Tue 2019-10-29 17:02:29
https://utcc.utoronto.ca/~cks/space/blog/unix/V7WhyItMattersSoMuch  found Mon 2022 -01-10 13:12:03 on https://irreal.org/blog/?p=10149
https://utcc.utoronto.ca/~cks/space/blog/linux/UbuntuKernelAutoremove  MIght want to see whether this is relevant for me. Saved Tue 2017-03-28 19:10:35

See the output of several compilers in your web browser.
In addition to C++, it now supports Go, Rust and D.

GNU Mes brings a Reduced Binary Seed bootstrap to GuixSD and potentially to any other interested GNU/Linux distribution, and aims to help create a full source bootstrap as part of the bootstrappable builds effort.

It consists of a mutual self-hosting Scheme interpreter written in ~5,000 LOC of simple C and a Nyacc-based C compiler written in Scheme. This mes.c is being simplified to be transpiled by M2-Planet.
https://github.com/oriansj/M2-Planet

The Scheme interpreter (mes.c) has a Garbage Collector, a library of loadable Scheme modules– notably Dominique Boucher's LALR, Pre-R6RS portable syntax-case with R7RS ellipsis, Matt Wette's Nyacc –and test suite just barely enough to support a simple REPL and simple C-compiler: MesCC.
https://github.com/oriansj/mescc-tools

Mes+MesCC can compile an only lightly patched TinyCC that is self-hosting. Using this tcc and the Mes C library we now have a Reduced Binary Seed bootstrap for the gnutools triplet: glibc-2.2.5, binutils-2.20.1, gcc-2.95.3. This is enough to bootstrap GuixSD for i686-linux and x8664-linux.

Mes is inspired by The Maxwell Equations of Software: LISP-1.5 – John McCarthy page 13, GNU Guix's source/binary packaging transparency and Jeremiah Orians's stage0 ~500 byte self-hosting hex assembler.

GNU Mes is free software, it is distributed under the terms of the GNU General Public Licence version 3 or later. See the file COPYING.

Various number theoretic algrorithms written in the bc(1) programming language.
See also the calculator program http://www.numbertheory.org/calc/krm_calc.htm from the same author.

RTags is a client/server application that indexes C/C++ code and keeps a persistent file-based database of references, declarations, definitions, symbolnames etc. There’s also limited support for ObjC/ObjC++. It allows you to find symbols by name (including nested class and namespace scope). Most importantly we give you proper follow-symbol and find-references support. We also have neat little things like rename-symbol, integration with clang’s “fixits” (http://clang.llvm.org/diagnostics.html). We also integrate with flymake using clang’s vastly superior errors and warnings. Since RTags constantly will reindex “dirty” files you get live updates of compiler errors and warnings. Since we already know how to compile your sources we have a way to quickly bring up the preprocessed output of the current source file in a buffer.

While existing taggers like gnu global, cscope, etags, ctags etc do a decent job for C they often fall a little bit short for C++. With its incredible lexical complexity, parsing C++ is an incredibly hard task and we make no bones about the fact that the only reason we are able to improve on the current tools is because of clang (http://clang.llvm.org/). RTags is named RTags in recognition of Roberto Raggi on whose C++ parser we intended to base this project but he assured us clang was the way to go. The name stuck though.