What’s new in C++11

| Apr 17, 2014

I always enjoy chatting with Steve Clamage about C++, and I was really pleased to get to interview him about what we should expect from the new 2011 standard.

Binding to the current processor

| May 30, 2013

Just hacked up a snippet of code to stop a thread migrating to a different CPU while it runs. This should help the thread get, and keep, local memory. This in turn should reduce run-to-run variance.

#include <sys/processor.h>

void bindnow()
{
  processorid_t proc = getcpuid();
  if (processor_bind(P_LWPID, P_MYID, proc,  (more...)

One executable, many platforms

| May 28, 2013

Different processors have different optimal sequences of code. Fortunately, most of the time the differences are minor, and we can easily accommodate them by generating generic code.

If you needed more than this, then the "old" model was to use dynamic string tokens to pick the best library for the (more...)

OpenMP and language level parallelisation

The C11 and C++11 standards introduced some very useful features into the language. In particular they provided language-level access to threading and synchronisation primitives. So using the new standards we can write multithreaded code that compiles and runs on standard compliant platforms. I've tackled translating Windows and POSIX threads before (more...)

The pains of preprocessing

| Mar 14, 2013

Ok, so I've encountered this twice in 24 hours. So it's probably worth talking about it.

The preprocessor does a simple text substitution as it works its way through your source files. Sometimes this has "unanticipated" side-effects. When this happens, you'll normally get a "hey, this makes no sense at all" error from the compiler. Here's an example:

$ more c.c
#include <ucontext.h>
#include <stdio.h>

int main()
{
  int FS;
  FS=0;
  printf("FS=%i",FS);
}

$ CC c.c
$ CC c.c
"c.c", line 6: Error: Badly formed expression.
"c.c", line 7: Error: The left operand  (more...)