diff options
Diffstat (limited to 'gcc/ada/types.ads')
| -rw-r--r-- | gcc/ada/types.ads | 59 |
1 files changed, 25 insertions, 34 deletions
diff --git a/gcc/ada/types.ads b/gcc/ada/types.ads index 277bfd55146..861c0bcc1c8 100644 --- a/gcc/ada/types.ads +++ b/gcc/ada/types.ads @@ -703,43 +703,39 @@ package Types is -- 4. Add a new Do_xxx_Check flag to Sinfo (if required) -- 5. Add appropriate checks for the new test - -- The following provides precise details on the mode used to check - -- intermediate overflows in expressions for signed integer arithmetic. + -- The following provides precise details on the mode used to generate + -- code for intermediate overflows in expressions for signed integer + -- arithmetic (and how to generate overflow checks if enabled). Note + -- that this only affects handling of intermediate results. The final + -- result must always fit within the target range, and if overflow + -- checking is enabled, the check on the final result is against this + -- target range. type Overflow_Check_Type is ( Not_Set, -- Dummy value used during initialization process to show that the -- corresponding value has not yet been initialized. - Suppressed, - -- Overflow checking is suppressed. If an arithmetic operation creates - -- an overflow, no exception is raised, and the program is erroneous. - - Checked, - -- All operations, including all intermediate operations are checked. - -- If the result of any arithmetic operation gives a result outside the - -- range of the base type, then a Constraint_Error exception is raised. + Strict, + -- Operations are done in the base type of the subexpression. If + -- overflow checks are enabled, then the check is against the range + -- of this base type. Minimized, - -- Where appropriate, arithmetic operations are performed with an - -- extended range, using Long_Long_Integer if necessary. As long as the - -- result fits in this extended range, then no exception is raised and - -- computation continues with the extended result. The final value of an - -- expression must fit in the base type of the whole expression. If an - -- intermediate result is outside the range of Long_Long_Integer then a - -- Constraint_Error exception is raised. + -- Where appropriate, intermediate arithmetic operations are performed + -- with an extended range, using Long_Long_Integer if necessary. If + -- overflow checking is enabled, then the check is against the range + -- of Long_Long_Integer. Eliminated); -- In this mode arbitrary precision arithmetic is used as needed to -- ensure that it is impossible for intermediate arithmetic to cause an - -- overflow. Again the final value of an expression must fit in the base - -- type of the whole expression. + -- overflow. In this mode, intermediate expressions are not affected by + -- the overflow checking mode, since overflows are eliminated. subtype Minimized_Or_Eliminated is Overflow_Check_Type range Minimized .. Eliminated; - subtype Suppressed_Or_Checked is - Overflow_Check_Type range Suppressed .. Checked; - -- Define subtypes so that clients don't need to know ordering. Note that + -- Define subtype so that clients don't need to know ordering. Note that -- Overflow_Check_Type is not marked as an ordered enumeration type. -- The following structure captures the state of check suppression or @@ -747,24 +743,19 @@ package Types is type Suppress_Record is record Suppress : Suppress_Array; - -- Indicates suppression status of each possible check. Note: there - -- is an entry for Overflow_Check in this array, but it is never used. - -- Instead we use the more detailed information in the two components - -- that follow this one (Overflow_Checks_General/Assertions). + -- Indicates suppression status of each possible check Overflow_Checks_General : Overflow_Check_Type; - -- This field indicates the mode of overflow checking to be applied to - -- general expressions outside assertions. + -- This field indicates the mode for handling code generation and + -- overflow checking (if enabled) for intermediate expression values. + -- This applies to general expressions outside assertions. Overflow_Checks_Assertions : Overflow_Check_Type; - -- This field indicates the mode of overflow checking to be applied to - -- any expression occuring inside assertions. + -- This field indicates the mode for handling code generation and + -- overflow checking (if enabled) for intermediate expression values. + -- This applies to any expression occuring inside assertions. end record; - Suppress_All : constant Suppress_Record := - ((others => True), Suppressed, Suppressed); - -- Constant used to initialize Suppress_Record value to all suppressed. - ----------------------------------- -- Global Exception Declarations -- ----------------------------------- |