pragma Suppress (Identifier [, [On =>] Name]);
This is a standard pragma, and supports all the check names required in the RM. It is included here because GNAT recognizes some additional check names that are implementation defined (as permitted by the RM):
Alignment_Check can be used to suppress alignment checks
on addresses used in address clauses. Such checks can also be suppressed
by suppressing range checks, but the specific use of Alignment_Check
allows suppression of alignment checks without suppressing other range checks.
Predicate_Check can be used to control whether predicate checks are
active. It is applicable only to predicates for which the policy is
Check. Unlike Assertion_Policy, which determines if a given
predicate is ignored or checked for the whole program, the use of
Suppress and Unsuppress with this check name allows a given
predicate to be turned on and off at specific points in the program.
Validity_Check can be used specifically to control validity checks.
If Suppress is used to suppress validity checks, then no validity
checks are performed, including those specified by the appropriate compiler
switch or the Validity_Checks pragma.
Check_Name
pragma are also allowed.
Note that pragma Suppress gives the compiler permission to omit checks, but does not require the compiler to omit checks. The compiler will generate checks if they are essentially free, even when they are suppressed. In particular, if the compiler can prove that a certain check will necessarily fail, it will generate code to do an unconditional “raise”, even if checks are suppressed. The compiler warns in this case.
Of course, run-time checks are omitted whenever the compiler can prove that they will not fail, whether or not checks are suppressed.