keeping simple

Category: systems

  • C Standards: the triumph of bureaucracy

    C Standards: the triumph of bureaucracy

      C89  The ANSI standard. C23 the most recent draft.  Three modest proposals for fixing the C standard.  PLOS paper ISO C is not suitable for operating systems.  Torvalds on aliasing.   Ritchie on aliasing. Three modest proposals for the C standard WG14      

  • C23 standard (final draft)

  • Kuth’s Merge Sort in C

    Kuth’s Merge Sort in C

    Taken from Knuth Algorithm S mergesort P162-163 Vol 3 Second edition 1998 The major change is that the scratch buffer is not required to be adjacent and there are some changes because C array indexing starts with 0.  This is very much how a mathematician writes code. You have to remember a larger than usual…

  • don’t defer

    There is a proposal to add “defer” to C. Its biggest example is taken from code that was originally designed to not manage storage at all, but to run once and exit – delegating all the cleanup to exit. The proposal authors show a complex solution to make the code free storage and then show…

  • Unforgivable C programming 1

    Here’s a program that exhibits the  low level nature of  C  by changing the return address of a function. The function “one” always returns the number 1 and the function “two” always returns the number 2. The main code calls “one” and prints out that it returned 1, then calls “two”  and then changes its…

  • Threads in C

    There is a nice example thread semantics in a paper by David Goldblatt (P1916R0)  which illustrates a couple of things about multi-core processing – including how interesting it is and how poorly defined the C11 atomic/thread extension is . A simplified version looks like this: //Example1 int x=0; int y=0; int r1=0; int r2 =0;…

  • PLOS 2021 paper: How ISO-C became unusable for operating system development

    PLOS 2021 paper: How ISO-C became unusable for operating system development

  • Memory model and semantics for C

    A perceptive note from Linus Torvalds about the C/C++ “memory model” is reproduced below. From Linus Torvalds <> Date Thu, 7 Jun 2018 08:40:49 -0700 Subject Re: LKMM litmus test for Roman Penyaev’s rcu-rr share 0 On Thu, Jun 7, 2018 at 7:57 AM Alan Stern <stern@rowland.harvard.edu> wrote: > > You can look at a…

  • unfashionable C

    unfashionable C

    In computer science academia, C  along with UNIX, and PDP11s, is as unfashionable as can be: the equivalent of other 1970’s relics, like polyester leisure suits and mullets. In 2018 ACM Queue published an essay by David Chisnall called: C Is Not a Low-level Language: Your computer is not a fast PDP-11  that expresses many…

  • Undefined behavior in C is a reading error.

    Considering how important “undefined behavior” has become to C semantics and the ISO/IEC JTC1/SC22/WG14 Committee, the lack of any reference to it in the K&R ANSI book is notable and the description in the 1999 C Rationale was quite modest. Undefined behavior gives the implementor license not to catch certain program errors that are difficult…