Why do I have a compilation issues with time.h ?

Question

MathWorks Support Team 2009-9-28

When working with the header file time.h, I receive the following error if I use the structure timespec even if the list of header files is correct:

 <file.c>: undefined size for `incomplete struct timespec defined at <file.c>:<line> timeout'

If I use the struct itimerspec, I receive the following error:

 Verifying test2.c
 <file.c>, line 6: error: incomplete type is not allowed

Line 6 is the line where itimerspec is used.

Answer 1

1. As one can see in the comment of the structure timespec in time.h, this structure is a POSIX structure.

The POSIX extension will be taken into account if you define the flag _GNU_SOURCE (see features.h)

2. For itimerspec, this structure is declared in

#include <linux/time.h>

Note that linux/time.h is not an Ansi include. And it actually contains non Ansi keywords, like '__signed__'.

So the compilation issue can be fixed by providing an include file that contains the following:

#define _GNU_SOURCE 1
#define __signed__
#include <linux/time.h>

This include file should be used with the option '-include'.