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(g77-295.info)Multiple Definitions of External Names

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Multiple Definitions of External Names
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   `g77' doesn't allow a common block and an external procedure or
`BLOCK DATA' to have the same name.  Some systems allow this, but `g77'
does not, to be compatible with `f2c'.

   `g77' could special-case the way it handles `BLOCK DATA', since it
is not compatible with `f2c' in this particular area (necessarily,
since `g77' offers an important feature here), but it is likely that
such special-casing would be very annoying to people with programs that
use `EXTERNAL FOO', with no other mention of `FOO' in the same program
unit, to refer to external procedures, since the result would be that
`g77' would treat these references as requests to force-load BLOCK DATA
program units.

   In that case, if `g77' modified names of `BLOCK DATA' so they could
have the same names as `COMMON', users would find that their programs
wouldn't link because the `FOO' procedure didn't have its name
translated the same way.

   (Strictly speaking, `g77' could emit a
null-but-externally-satisfying definition of `FOO' with its name
transformed as if it had been a `BLOCK DATA', but that probably invites
more trouble than it's worth.)