Syntax:
pragma Style_Checks (string_LITERAL | ALL_CHECKS | On | Off [, LOCAL_NAME]);
This pragma is used in conjunction with compiler switches to control the
built in style checking provided by GNAT. The compiler switches, if set,
provide an initial setting for the switches, and this pragma may be used
to modify these settings, or the settings may be provided entirely by
the use of the pragma. This pragma can be used anywhere that a pragma
is legal, including use as a configuration pragma (including use in
the gnat.adc
file).
The form with a string literal specifies which style options are to be activated. These are additive, so they apply in addition to any previously set style check options. The codes for the options are the same as those used in the ‘-gnaty’ switch to ‘gcc’ or ‘gnatmake’. For example the following two methods can be used to enable layout checking and to change the maximum nesting level value:
-- switch on layout checks pragma Style_Checks ("l"); -- set the number of maximum allowed nesting levels to 15 pragma Style_Checks ("L15");
gcc -c -gnatyl -gnatyL15 ...
The string literal values can be cumulatively switched on and off by prefixing
the value with +
or -
, where:
+
is equivalent to no prefix. It applies the check referenced by the
literal value;
-
switches the referenced check off.
-- allow misaligned block by disabling layout check pragma Style_Checks ("-l"); declare msg : constant String := "Hello"; begin Put_Line (msg); end; -- enable the layout check again pragma Style_Checks ("l"); declare msg : constant String := "Hello"; begin Put_Line (msg); end;
The code above contains two layout errors, however, only the last line is picked up by the compiler.
Similarly, the switches containing a numeric value can be applied in sequence. In the example below, the permitted nesting level is reduced in in the middle block and the compiler raises a warning on the highlighted line.
-- Permit 3 levels of nesting pragma Style_Checks ("L3"); procedure Main is begin if True then if True then null; end if; end if; -- Reduce permitted nesting levels to 2. -- Note that "+L2" and "L2" are equivalent. pragma Style_Checks ("+L2"); if True then if True then null; end if; end if; -- Disable checking permitted nesting levels. -- Note that the number after "-L" is insignificant, -- "-L", "-L3" and "-Lx" are all equivalent. pragma Style_Checks ("-L3"); if True then if True then null; end if; end if; end Main;
The form ALL_CHECKS
activates all standard checks (its use is equivalent
to the use of the gnaty
switch with no options.
See the GNAT User’s Guide for details.)
Note: the behavior is slightly different in GNAT mode (-gnatg
used).
In this case, ALL_CHECKS
implies the standard set of GNAT mode style check
options (i.e. equivalent to -gnatyg
).
The forms with Off
and On
can be used to temporarily disable style checks
as shown in the following example:
pragma Style_Checks ("k"); -- requires keywords in lower case pragma Style_Checks (Off); -- turn off style checks NULL; -- this will not generate an error message pragma Style_Checks (On); -- turn style checks back on NULL; -- this will generate an error message
Finally the two argument form is allowed only if the first argument is
On
or Off
. The effect is to turn of semantic style checks
for the specified entity, as shown in the following example:
pragma Style_Checks ("r"); -- require consistency of identifier casing Arg : Integer; Rf1 : Integer := ARG; -- incorrect, wrong case pragma Style_Checks (Off, Arg); Rf2 : Integer := ARG; -- OK, no error