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(g77-300.info)Transforming Block IF

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Transforming Block IF
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   Consider:

     SUBROUTINE X(A,B,C)
     CHARACTER*(*) A, B, C
     LOGICAL LFUNC
     
     IF (LFUNC (A//B)) THEN
       CALL SUBR1
     ELSE IF (LFUNC (A//C)) THEN
       CALL SUBR2
     ELSE
       CALL SUBR3
     END

   The arguments to the two calls to `LFUNC' require dynamic allocation
(at run time), but are not required during execution of the `CALL'
statements.

   So, the scopes of those temporaries must be within blocks inside the
block corresponding to the Fortran `IF' block.

   This cannot be represented "naturally" in vanilla C, nor in GBEL.
The `if', `elseif', `else', and `endif' constructs provided by both
languages must, for a given `if' block, share the same C/GBE block.

   Therefore, any temporaries needed during evaluation of `expr' while
executing `ELSE IF(expr)' must either have been predeclared at the top
of the corresponding `IF' block, or declared within a new block for
that `ELSE IF'--a block that, since it cannot contain the `else' or
`else if' itself (due to the above requirement), actually implements
the rest of the `IF' block's `ELSE IF' and `ELSE' statements within an
inner block.

   The FFE takes the latter approach.