Labeled COMMON

Fortran labeled COMMON can be emulated in C by using a global struct.

Table 11-16 Emulating Labeled COMMON

Fortran COMMON Definition	C "COMMON" Definition
COMMON /BLOCK/ ALPHA,NUM ...	extern struct block { float alpha; int num; }; extern struct block block_ ; main () { ... block_.alpha = 32.; block_.num += 1; ... }

Note that the external name established by the C routine must end in an underscore to link with the block created by the Fortran program. Note also that the C directive #pragma pack may be needed to get the same padding as with Fortran. Both f77 and f90 align data in COMMON blocks to at most 4-byte boundaries.