For portability to machines where a pointer (such as to a label,
which is how g77 implements ASSIGN and its relatives,
the assigned-GOTO and assigned-FORMAT-I/O statements)
is wider (bitwise) than an INTEGER(KIND=1), g77
uses a different memory location to hold the ASSIGNed value of a variable
than it does the numerical value in that variable, unless the
variable is wide enough (can hold enough bits).
In particular, while g77 implements
I = 10
as, in C notation, `i = 10;', it implements
ASSIGN 10 TO I
as, in GNU's extended C notation (for the label syntax),
`__g77_ASSIGN_I = &&L10;' (where `L10' is just a massaging
of the Fortran label `10' to make the syntax C-like; g77 doesn't
actually generate the name `L10' or any other name like that,
since debuggers cannot access labels anyway).
While this currently means that an ASSIGN statement does not
overwrite the numeric contents of its target variable, do not
write any code depending on this feature.
g77 has already changed this implementation across
versions and might do so in the future.
This information is provided only to make debugging Fortran programs
compiled with the current version of g77 somewhat easier.
If there's no debugger-visible variable named `__g77_ASSIGN_I'
in a program unit that does `ASSIGN 10 TO I', that probably
means g77 has decided it can store the pointer to the label directly
into `I' itself.
See section Ugly Assigned Labels, for information on a command-line option
to force g77 to use the same storage for both normal and
assigned-label uses of a variable.
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