Sophie: ftnchek-3.1.2-2mdk i586

ftnchek-3.1.2-2mdk.i586.rpm

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<TITLE>Option: usage</TITLE>
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<H2>Option: <font color=#FF0080>usage</font></H2><P>
<A NAME="usage"></A><DT><B><A HREF="usage.html">-usage</A>=</B><I>list</I>

<DD>
<DL COMPACT><DT><DD>
Warn about unused or possible uninitialized variables,
unused common blocks, undefined or unused statement labels, and unused or undefined subprograms.
By default, all warnings are
turned on.
<P>

This setting provides detailed control over the warnings about
possible usage errors.  The <I>list</I> consists of keywords
separated by commas or colons.
Since all warnings are on by default, include a keyword prefixed by
<B>no-</B> to turn off a particular warning.
There are three special keywords: <B>all</B> to turn on all the
warnings about usage, <B>none</B> to turn them all
off, and <B>help</B> to print the list of all the keywords with a brief
explanation of each.
If <I>list</I> is omitted, <B><A HREF="usage.html">-usage</A></B> is equivalent to
<B><A HREF="usage.html">-usage</A>=all</B>, and <B>-nousage</B> is equivalent to
<B><A HREF="usage.html">-usage</A>=none</B>.
These warnings cover four main categories of objects: subprogram dummy
arguments, common blocks and variables, subprograms and functions, and
local variables.  Warnings include undefined items, multiply defined
items, unused items, etc.
The warning keywords with their meanings are as follows:
<DL COMPACT>
<DT><B>arg-alias</B>:

<DD>
a scalar dummy argument is actually the same as another and is (or may be)
modified.  The Fortran 77 standard (section 15.9.3.6) prohibits
modifying an argument that is aliased to another.
<DT><B>arg-array-alias</B>:

<DD>
a dummy argument which is an array or array element is in the same array as
another and is modified.  This flag is similar to <B>arg-alias</B> but
provides separate control over array arguments.  It is harder to
tell if aliasing is occurring in the case of arrays, so if
<B>ftnchek</B> gives too many false warnings, this flag allows the
array-related ones to be turned off without suppressing the warnings
for scalars.
<DT><B>arg-common-alias</B>:

<DD>
a scalar dummy argument is the same as a common variable in the
subprogram, and either is modified.  This is also prohibited by the
Fortran 77 standard.  If common checking is not exact (see the
<B><A HREF="common.html">-common</A></B> setting), it is harder to tell if aliasing is
occurring, so the warning is
given if the variable is anywhere in a common block that is declared
by the subprogram.
<DT><B>arg-common-array-alias</B>:

<DD>
a dummy argument which is an array or array element is in the same
array as a common variable, and either is modified.  If common
checking is not exact, the variable can be anywhere in a common block
that is declared by the subprogram.
<DT><B>arg-const-modified</B>:

<DD>
a subprogram modifies an argument which is a constant or an
expression.  Such an action could cause anomalous behavior of the program.
<DT><B>arg-unused</B>:

<DD>
a dummy argument is declared but never used.  This is similar to the
<B>var-unused</B> keyword described below, but applies only to arguments.
<DT><B>com-block-unused</B>:

<DD>
a common block is declared but none of the variables in it are
used by any subprogram.
This warning is suppressed if the common strictness setting is 0.
<DT><B>com-block-volatile</B>:

<DD>
a common block may lose the definition of its contents if common
blocks are volatile.  This option only has an effect if the
<B><A HREF="common.html">-common</A>=volatile</B> flag is in effect.  See the discussion of the
<B><A HREF="common.html">-common</A></B> setting above.
<DT><B>com-var-set-unused</B>:

<DD>
a common variable is assigned a value, but its value is not used by
any subprogram.
This warning is suppressed if the common strictness setting is 0.
<DT><B>com-var-uninitialized</B>:

<DD>
a common variable's value is used in some subprogram, but is not set
anywhere.
Unfortunately, <B>ftnchek</B> does
not do a thorough enough analysis of the calling sequence to know
which routines are called before others.  So warnings about this type
of error will only be given for cases in which a variable is used in
some routine but not set in any other routine.   Checking of
individual COMMON variables is done only if the <B><A HREF="common.html">-common</A></B>
setting is 3 (variable by variable agreement).
This warning is suppressed if the common strictness setting is 0.
<DT><B>com-var-unused</B>:

<DD>
a common variable is declared but not used by any subprogram.
This warning is suppressed if the common strictness setting is 0.
<DT><B>do-index-modified</B>:

<DD>
a variable that is the index of a DO loop is modified by some
statement within the range of the loop.  The Standard permits an
active DO variable to be modified only by the incrementation mechanism
of the DO statement.
<DT><B>ext-multiply-defined</B>:

<DD>
an external (a subroutine or function) is defined more than once.
Definition of an external means providing the body of its source code.
<DT><B>ext-declared-only</B>:

<DD>
a name is declared in an EXTERNAL statement in some module, but
is not defined or used anywhere.
<DT><B>ext-undefined</B>:

<DD>
an external is used (invoked) but not defined anywhere.  This option
is equivalent to the <B><A HREF="extern.html">-extern</A>al</B> flag.  If the subprogram is
invoked more than once, those invocations will still be checked for
consistency.
<DT><B>ext-unused</B>:

<DD>
an external is defined (its subprogram body is present) but it is not
used.  A subprogram is considered unused even if it is
invoked by some other subprogram, if it cannot be called from any thread
of execution starting with the main program.
The agreement of the subprogram's
arguments with its invocations is still checked even if this warning is
turned off.
If there is no main program, then this warning is issued only if the
subprogram is not invoked anywhere.
This warning is suppressed in library mode, but library mode has the
additional effect of suppressing argument checking for unused routines.
<DT><B>label-undefined</B>:

<DD>
a statement refers to a label that has not been defined.
<DT><B>label-unused</B>:

<DD>
a statement label is defined, but never referred to.
<DT><B>var-set-unused</B>:

<DD>
a local variable is assigned a value, but that value is not used.
<DT><B>var-uninitialized</B>:

<DD>
a local variable's value may be used before it is assigned.
Sometimes <B>ftnchek</B> makes a mistake in the warnings about local
variable usage.  Usually it errs on the side of giving a warning where no
problem exists, but in rare cases it may fail to warn where the
problem does exist.  See the section on Bugs for examples.  If
variables are equivalenced, the rule used by <B>ftnchek</B> is that a
reference to any variable implies the same reference to all variables
it is equivalenced to.  For arrays, the rule is that a reference to
any array element is treated as a reference to all elements of the array.
<DT><B>var-unused</B>:

<DD>
a local variable is declared (for instance, in a type declaration) but
is not used in the module.  Does not apply to dummy arguments: warnings
about them are controlled by the keyword <B>arg-unused</B> described above.
</DL>
<P>

Note: In versions of <B>ftnchek</B> prior to 2.10, the
<B><A HREF="usage.html">-usage</A></B> flag took a numeric argument instead of a list of
options.
For the sake of users who may have written scripts invoking
<B>ftnchek</B> in this way, the numeric form is still
accepted.  The numeric setting is composed of three digits.  The first
digit (hundreds
place) controls warnings about subprograms (functions and
subroutines), the second digit (tens place) warnings about common
blocks and common variables,, and the third digit (ones place)
warnings about local variables.  Each digit controls warnings
according to the convention that a 1 means warn about undefined items
and variables that are used before set,
a 2 means warn about items that are unused, and a 3 means warn about
both types.  These numbers are now converted to the appropriate
values for the above-listed keywords, except for <B>com-block-volatile</B>,
which is not affected by the numeric argument.
<P>

See also: <B><A HREF="common.html">-common</A></B>, <B><A HREF="declare.html">-declare</A></B>, <B><A HREF="extern.html">-extern</A></B>,
<B><A HREF="library.html">-library</A></B>.
</DL>

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