gfortran on MacOS X

How to Install a Precompiled Binary Package

A binary package is available as an RPM which can be installed using APT/RPM as

$ sudo apt-get update
$ sudo apt-get install gcc
$ sudo apt-get clean

Notice that this will replace your default gcc compilers (gcc and g++), which is necessary to allow mixed use of C, C++, and FORTRAN for a single application. The default gcc compilers can be switched by using the "update-altarnatives" command as follows and answering the questions:

$ sudo update-alternatives --config gcc


 

REMARKS

• As a general rule, you should make sure that optimization does not change your results.
• Avoid too many else if's in the same level. You sometimes need to nest them, if the compiler abends.
• gfortran forbids jumping into a different "IF" block.
• gfortran does not initialize a "BLOCK DATA" even if you declare it "EXTERNAL". In order to force it, say "blkdat", initialized, I needed a trick like
  
      external blkdat
      call dummysub(blkdat)
  
  with
      subroutine dummysub(a)
      return
      end
  
  
• gfortran now returns IOSTAT=5002 (instead of IOSTAT=3 as with gcc-4.2 or older), when the EOF is reached for an random access file, which behavior is different from that of g77.
• gcc, g++, and gfortran now use system's math library (libm.dylib), whenever possible, which sometimes causes a problem, since some functions in libm behave differently from those used to be supplied by gcc-associated libraries (a typical example is "csqrt": see cernlib page).
• Here is a sample FCFLAGS I usually use to compile my legacy fortran programs:
  
      FCFLAGS = -fno-automatic -fno-second-underscore -fno-range-check