ftnchek will give warnings for a variety of
non-portable usages. Examples include the use of tabs except in comments
or inside strings, the use of Hollerith constants, and the
equivalencing of variables of different data types. This option does
not produce warnings for supported extensions to the Fortran 77 Standard, which
may also cause portability problems. To catch those, use
the -f77 setting.
By default, all warnings are turned off.
This setting provides detailed control over the warnings about
possible portability problems. The list consists of keywords
separated by commas or colons.
There are three special keywords: all to turn on all the
warnings about nonportable usages, none to turn them all
off, and help to print the list of all the keywords with a brief
explanation of each.
If list is omitted, -portability is equivalent to
-portability=all, and -noportability is equivalent to
The warning keywords with their meanings are as follows:
Backslash character in strings. Since some compilers treat the
backslash as an escape character, its presence can cause problems even
though it is used in a standard-conforming way.
COMMON block variables not in descending order of storage size. Some
compilers require this ordering because of storage alignment requirements.
Hollerith constants (other than within FORMAT
specifications). The Hollerith data type is a feature of Fortran IV
that has been deleted in the Fortran 77 standard. It is superseded
by the character data type. Storing Hollerith data in variables of a
numeric or logical data type is nonportable due to differing word sizes.
String constants, variables, or expressions over 255 chars long.
Variables of different data types equivalenced.
Variables declared with default precision used with variables given
explicit precision, in expressions, assignments, or as arguments. For
example, if a variable declared as REAL*8 is treated as
equivalent to DOUBLE PRECISION.
Non-integer DO loop index and bounds. These can cause a program's
results to depend on the hardware characteristics of the particular
Implicit typing of a parameter by the data type of the value assigned,
if it differs from the default type. This warning can only occur if
implicit parameter typing has been turned on by the
-source=param-implicit-type option, or
if the PARAMETER statement is of the nonstandard form without
parentheses. If this option is turned on,
then any instances where implicit parameter typing
occurs and where the implicit type is different from the default type based
on the first letter of the parameter name, will be warned
about. Implicit parameter typing can change the
semantics of statements where the parameter is used, causing
Tabs in source code. Tabs are interpreted differently by different
compilers. This warning will be given only once, at the end of the
See also: -f77, -f90, -f95,
-pretty, -style, -wordsize.