Fortran interface to the C standard library

Work in progress...

To compile with gfortran:

gcc -Wall -c libc.c -no-pie
gfortran -cpp -Wall -no-pie libc.o test_libc.f90 -o test_libc

On Linux, the flag -no-pie is needed to generate a non-position independent executable. See the following discussions:

To compile with the Intel compilers:

icc -c libc.c
ifort -fpp -warn all libc.o test_libc.f90 -o test_libc

Examples

See the file test_libc.f90 for usage examples following those available at http://www.cplusplus.com/reference/ctime/

When compiled with gfortran, if mktime (or its Fortran wrapper) is called twice it somehow corrupts memory and issues a double free or corruption error. If the size of the tm struct is increased from 9 to at least 11 integers, then it works properly on both compilers. See also:
- Size of struct tm; The glibc version of struct tm has two additional fields tm_gmtoff and tm_zone for the seconds east of UTC and the timezone abbreviation, respectively.
In some circumstances on the Fortran side the opaque pointers to the time_t and struct tm need to be declared as target in order to be able to call c_loc on the internal type(c_ptr) variable.