Errors on Mac OS X 10.6 “Snow Leopard” When COMMON Block Shares name with Library Routine

Problem :  On Mac OS X 10.6.x “Snow Leopard”, Fortran programs that declare COMMON blocks may have unexpected behavior, including “bus error”, if the COMMON block shares a name with a routine in a static library that is linked against.

Environment :  Mac OS 10.6.x with Xcode 3.2.1

Root Cause : Apple has confirmed that this is caused by a defect in the linker supplied with Mac OS 10.6, which is ld64-95.2.12 and newer versions of ld. To follow the issue and its eventual resolution, please refer to the known defect number 7890410 at

Resolution : If you wish to have Apple notify you when this issue is resolved, file a bug report at

Workaround: Rename the COMMON block so as not to duplicate a name in a static library.

Example: A COMMON block named SEED will cause problems because the Intel Fortran run-time library contains a portability routine named SEED.

Solution: By simply renaming the SEED common block in the example code below to something like ABCD, this code will not encounter the Sigbus crash.

program fixcommon


      iseed = 1
      write(6,*) 'done'

For more complete information about compiler optimizations, see our Optimization Notice.