Table of Contents
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 -portability=none
. 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It is superseded by the character data type.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
- 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 computer used.
- 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=parameter-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 portability problems.
- Tabs in source
code. Tabs are interpreted differently by different compilers. This warning
will be given only once, at the end of the file.
See also: -f77 , -f90 ,
-f95 , -pretty , -wordsize .