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(g77-295.info)Ugly Assigned Labels

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Ugly Assigned Labels
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   The `-fugly-assign' option forces `g77' to use the same storage for
assigned labels as it would for a normal assignment to the same
variable.

   For example, consider the following code fragment:

     I = 3
     ASSIGN 10 TO I

Normally, for portability and improved diagnostics, `g77' reserves
distinct storage for a "sibling" of `I', used only for `ASSIGN'
statements to that variable (along with the corresponding
assigned-`GOTO' and assigned-`FORMAT'-I/O statements that reference the
variable).

   However, some code (that violates the ANSI FORTRAN 77 standard)
attempts to copy assigned labels among variables involved with `ASSIGN'
statements, as in:

     ASSIGN 10 TO I
     ISTATE(5) = I
     ...
     J = ISTATE(ICUR)
     GOTO J

Such code doesn't work under `g77' unless `-fugly-assign' is specified
on the command-line, ensuring that the value of `I' referenced in the
second line is whatever value `g77' uses to designate statement label
`10', so the value may be copied into the `ISTATE' array, later
retrieved into a variable of the appropriate type (`J'), and used as
the target of an assigned-`GOTO' statement.

   *Note:* To avoid subtle program bugs, when `-fugly-assign' is
specified, `g77' requires the type of variables specified in
assigned-label contexts *must* be the same type returned by `%LOC()'.
On many systems, this type is effectively the same as
`INTEGER(KIND=1)', while, on others, it is effectively the same as
`INTEGER(KIND=2)'.

   Do *not* depend on `g77' actually writing valid pointers to these
variables, however.  While `g77' currently chooses that implementation,
it might be changed in the future.

   Note: Assigned Statement Labels (ASSIGN and GOTO),
 for implementation details on assigned-statement
labels.