Node: Style Checking, Next: Using gcc for Syntax Checking, Previous: Validity Checking, Up: Switches for gcc
The -gnatyx switch causes the compiler to enforce specified style rules. A limited set of style rules has been used in writing the GNAT sources themselves. This switch allows user programs to activate all or some of these checks. If the source program fails a specified style check, an appropriate warning message is given, preceded by the character sequence "(style)". The string x is a sequence of letters or digits indicating the particular style checks to be performed. The following checks are defined:
1-9 (specify indentation level)
-gnaty
then proper
indentation is checked, with the digit indicating the indentation level
required. The general style of required indentation is as specified by
the examples in the Ada Reference Manual. Full line comments must be
aligned with the --
starting on a column that is a multiple of
the alignment level.
a (check attribute casing)
-gnaty
then
attribute names, including the case of keywords such as digits
used as attributes names, must be written in mixed case, that is, the
initial letter and any letter following an underscore must be uppercase.
All other letters must be lowercase.
b (blanks not allowed at statement end)
-gnaty
then
trailing blanks are not allowed at the end of statements. The purpose of this
rule, together with h (no horizontal tabs), is to enforce a canonical format
for the use of blanks to separate source tokens.
c (check comments)
-gnaty
then
comments must meet the following set of rules:
gnatprep
(where -! is used) and the SPARK annnotation
language (where -# is used). For the purposes of this rule, a special
character is defined as being in one of the ASCII ranges
16#21#..16#2F# or 16#3A#..16#3F#.
--------------------------- -- This is a box comment -- -- with two text lines. -- ---------------------------
e (check end/exit labels)
-gnaty
then
optional labels on end
statements ending subprograms and on
exit
statements exiting named loops, are required to be present.
f (no form feeds or vertical tabs)
-gnaty
then
neither form feeds nor vertical tab characters are not permitted
in the source text.
h (no horizontal tabs)
-gnaty
then
horizontal tab characters are not permitted in the source text.
Together with the b (no blanks at end of line) check, this
enforces a canonical form for the use of blanks to separate
source tokens.
i (check if-then layout)
-gnaty
,
then the keyword then
must appear either on the same
line as corresponding if
, or on a line on its own, lined
up under the if
with at least one non-blank line in between
containing all or part of the condition to be tested.
k (check keyword casing)
-gnaty
then
all keywords must be in lower case (with the exception of keywords
such as digits
used as attribute names to which this check
does not apply).
l (check layout)
-gnaty
then
layout of statement and declaration constructs must follow the
recommendations in the Ada Reference Manual, as indicated by the
form of the syntax rules. For example an else
keyword must
be lined up with the corresponding if
keyword.
There are two respects in which the style rule enforced by this check
option are more liberal than those in the Ada Reference Manual. First
in the case of record declarations, it is permissible to put the
record
keyword on the same line as the type
keyword, and
then the end
in end record
must line up under type
.
For example, either of the following two layouts is acceptable:
type q is record a : integer; b : integer; end record; type q is record a : integer; b : integer; end record; |
Second, in the case of a block statement, a permitted alternative
is to put the block label on the same line as the declare
or
begin
keyword, and then line the end
keyword up under
the block label. For example both the following are permitted:
Block : declare A : Integer := 3; begin Proc (A, A); end Block; Block : declare A : Integer := 3; begin Proc (A, A); end Block; |
The same alternative format is allowed for loops. For example, both of the following are permitted:
Clear : while J < 10 loop A (J) := 0; end loop Clear; Clear : while J < 10 loop A (J) := 0; end loop Clear; |
m (check maximum line length)
-gnaty
then the length of source lines must not exceed 79 characters, including
any trailing blanks. The value of 79 allows convenient display on an
80 character wide device or window, allowing for possible special
treatment of 80 character lines.
Mnnn (set maximum line length)
-gnaty
then the length of lines must not exceed the
given value.
n (check casing of entities in Standard)
-gnaty
then any identifier from Standard must be cased
to match the presentation in the Ada Reference Manual (for example,
Integer
and ASCII.NUL
).
o (check order of subprogram bodies)
-gnaty
then all subprogram bodies in a given scope
(e.g. a package body) must be in alphabetical order. The ordering
rule uses normal Ada rules for comparing strings, ignoring casing
of letters, except that if there is a trailing numeric suffix, then
the value of this suffix is used in the ordering (e.g. Junk2 comes
before Junk10).
p (check pragma casing)
-gnaty
then
pragma names must be written in mixed case, that is, the
initial letter and any letter following an underscore must be uppercase.
All other letters must be lowercase.
r (check references)
-gnaty
then all identifier references must be cased in the same way as the
corresponding declaration. No specific casing style is imposed on
identifiers. The only requirement is for consistency of references
with declarations.
s (check separate specs)
-gnaty
then
separate declarations ("specs") are required for subprograms (a
body is not allowed to serve as its own declaration). The only
exception is that parameterless library level procedures are
not required to have a separate declaration. This exception covers
the most frequent form of main program procedures.
t (check token spacing)
-gnaty
then
the following token spacing rules are enforced:
abs
and not
must be followed by a space.
=>
must be surrounded by spaces.
<>
must be preceded by a space or a left parenthesis.
**
must be surrounded by spaces.
There is no restriction on the layout of the **
binary operator.
In the above rules, appearing in column one is always permitted, that is, counts as meeting either a requirement for a required preceding space, or as meeting a requirement for no preceding space.
Appearing at the end of a line is also always permitted, that is, counts as meeting either a requirement for a following space, or as meeting a requirement for no following space.
If any of these style rules is violated, a message is generated giving
details on the violation. The initial characters of such messages are
always "(style)". Note that these messages are treated as warning
messages, so they normally do not prevent the generation of an object
file. The -gnatwe
switch can be used to treat warning messages,
including style messages, as fatal errors.
The switch
-gnaty
on its own (that is not followed by any letters or digits),
is equivalent to gnaty3abcefhiklmprst
, that is all checking
options are enabled with
the exception of -gnatyo,
with an indentation level of 3. This is the standard
checking option that is used for the GNAT sources.