Code containing inconsistent calling sequences in the same file is
normally rejected--see GLOBALS.
(Use, say, ftnchek to ensure
consistency across source files.
See Generating Skeletons and Prototypes with f2c.)
Mysterious errors, which may appear to be code generation problems, can
appear specifically on the x86 architecture with some such
inconsistencies. On x86 hardware, floating-point return values of
functions are placed on the floating-point unit's register stack, not
the normal stack. Thus calling a REAL or DOUBLE PRECISION
FUNCTION as some other sort of procedure, or vice versa,
scrambles the floating-point stack. This may break unrelated code
executed later. Similarly if, say, external C routines are written
incorrectly.