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In addition to the implementation dependent pragmas and attributes, and the implementation advice, there are a number of other Ada features that are potentially implementation dependent and are designated as implementation-defined. These are mentioned throughout the Ada Reference Manual, and are summarized in Annex M.
A requirement for conforming Ada compilers is that they provide documentation describing how the implementation deals with each of these issues. In this chapter, you will find each point in Annex M listed followed by a description in italic font of how GNAT handles the implementation dependence.
You can use this chapter as a guide to minimizing implementation dependent features in your programs if portability to other compilers and other operating systems is an important consideration. The numbers in each section below correspond to the paragraph number in the Ada Reference Manual.
2. Whether or not each recommendation given in Implementation Advice is followed. See 1.1.2(37). See section 4. Implementation Advice.
3. Capacity limitations of the implementation. See 1.1.3(3). The complexity of programs that can be processed is limited only by the total amount of available virtual memory, and disk space for the generated object files.
4. Variations from the standard that are impractical to avoid given the implementation's execution environment. See 1.1.3(6). There are no variations from the standard.
5. Which code_statement
s cause external
interactions. See 1.1.3(10).
Any code_statement
can potentially cause external interactions.
6. The coded representation for the text of an Ada program. See 2.1(4). See separate section on source representation.
7. The control functions allowed in comments. See 2.1(14). See separate section on source representation.
8. The representation for an end of line. See 2.2(2). See separate section on source representation.
9. Maximum supported line length and lexical element length. See 2.2(15). The maximum line length is 255 characters and the maximum length of a lexical element is also 255 characters.
10. Implementation defined pragmas. See 2.8(14).
See section 1. Implementation Defined Pragmas.
11. Effect of pragma Optimize
. See 2.8(27).
Pragma Optimize
, if given with a Time
or Space
parameter, checks that the optimization flag is set, and aborts if it is
not.
12. The sequence of characters of the value returned by
S'Image
when some of the graphic characters of
S'Wide_Image
are not defined in Character
. See
3.5(37).
The sequence of characters is as defined by the wide character encoding
method used for the source. See section on source representation for
further details.
13. The predefined integer types declared in
Standard
. See 3.5.4(25).
Short_Short_Integer
Short_Integer
Integer
Long_Integer
Long_Long_Integer
14. Any nonstandard integer types and the operators defined for them. See 3.5.4(26). There are no nonstandard integer types.
15. Any nonstandard real types and the operators defined for them. See 3.5.6(8). There are no nonstandard real types.
16. What combinations of requested decimal precision and range are supported for floating point types. See 3.5.7(7). The precision and range is as defined by the IEEE standard.
17. The predefined floating point types declared in
Standard
. See 3.5.7(16).
Short_Float
Float
Long_Float
Long_Long_Float
18. The small of an ordinary fixed point type. See 3.5.9(8).
Fine_Delta
is 2**(-63)
19. What combinations of small, range, and digits are
supported for fixed point types. See 3.5.9(10).
Any combinations are permitted that do not result in a small less than
Fine_Delta
and do not result in a mantissa larger than 63 bits.
If the mantissa is larger than 53 bits on machines where Long_Long_Float
is 64 bits (true of all architectures except ia32), then the output from
Text_IO is accurate to only 53 bits, rather than the full mantissa. This
is because floating-point conversions are used to convert fixed point.
20. The result of Tags.Expanded_Name
for types declared
within an unnamed block_statement
. See 3.9(10).
Block numbers of the form Bnnn
, where nnn is a
decimal integer are allocated.
21. Implementation-defined attributes. See 4.1.4(12). See section 2. Implementation Defined Attributes.
22. Any implementation-defined time types. See 9.6(6). There are no implementation-defined time types.
23. The time base associated with relative delays.
See 9.6(20). The time base used is that provided by the C library
function gettimeofday
.
24. The time base of the type Calendar.Time
. See
9.6(23).
The time base used is that provided by the C library function
gettimeofday
.
25. The time zone used for package Calendar
operations. See 9.6(24).
The time zone used by package Calendar
is the current system time zone
setting for local time, as accessed by the C library function
localtime
.
26. Any limit on delay_until_statements
of
select_statements
. See 9.6(29).
There are no such limits.
27. Whether or not two non-overlapping parts of a composite
object are independently addressable, in the case where packing, record
layout, or Component_Size
is specified for the object. See
9.10(1).
Separate components are independently addressable if they do not share
overlapping storage units.
28. The representation for a compilation. See 10.1(2).
A compilation is represented by a sequence of files presented to the
compiler in a single invocation of the gcc
command.
29. Any restrictions on compilations that contain multiple compilation_units. See 10.1(4). No single file can contain more than one compilation unit, but any sequence of files can be presented to the compiler as a single compilation.
30. The mechanisms for creating an environment and for adding and replacing compilation units. See 10.1.4(3). See separate section on compilation model.
31. The manner of explicitly assigning library units to a partition. See 10.2(2). If a unit contains an Ada main program, then the Ada units for the partition are determined by recursive application of the rules in the Ada Reference Manual section 10.2(2-6). In other words, the Ada units will be those that are needed by the main program, and then this definition of need is applied recursively to those units, and the partition contains the transitive closure determined by this relationship. In short, all the necessary units are included, with no need to explicitly specify the list. If additional units are required, e.g. by foreign language units, then all units must be mentioned in the context clause of one of the needed Ada units.
If the partition contains no main program, or if the main program is in a language other than Ada, then GNAT provides the binder options `-z' and `-n' respectively, and in this case a list of units can be explicitly supplied to the binder for inclusion in the partition (all units needed by these units will also be included automatically). For full details on the use of these options, refer to section `The GNAT Make Program gnatmake' in GNAT User's Guide.
32. The implementation-defined means, if any, of specifying which compilation units are needed by a given compilation unit. See 10.2(2). The units needed by a given compilation unit are as defined in the Ada Reference Manual section 10.2(2-6). There are no implementation-defined pragmas or other implementation-defined means for specifying needed units.
33. The manner of designating the main subprogram of a partition. See 10.2(7). The main program is designated by providing the name of the corresponding `ALI' file as the input parameter to the binder.
34. The order of elaboration of library_items
. See
10.2(18).
The first constraint on ordering is that it meets the requirements of
Chapter 10 of the Ada Reference Manual. This still leaves some
implementation dependent choices, which are resolved by first
elaborating bodies as early as possible (i.e., in preference to specs
where there is a choice), and second by evaluating the immediate with
clauses of a unit to determine the probably best choice, and
third by elaborating in alphabetical order of unit names
where a choice still remains.
35. Parameter passing and function return for the main
subprogram. See 10.2(21).
The main program has no parameters. It may be a procedure, or a function
returning an integer type. In the latter case, the returned integer
value is the return code of the program (overriding any value that
may have been set by a call to Ada.Command_Line.Set_Exit_Status
).
36. The mechanisms for building and running partitions. See 10.2(24). GNAT itself supports programs with only a single partition. The GNATDIST tool provided with the GLADE package (which also includes an implementation of the PCS) provides a completely flexible method for building and running programs consisting of multiple partitions. See the separate GLADE manual for details.
37. The details of program execution, including program termination. See 10.2(25). See separate section on compilation model.
38. The semantics of any non-active partitions supported by the implementation. See 10.2(28). Passive partitions are supported on targets where shared memory is provided by the operating system. See the GLADE reference manual for further details.
39. The information returned by Exception_Message
. See
11.4.1(10).
Exception message returns the null string unless a specific message has
been passed by the program.
40. The result of Exceptions.Exception_Name
for types
declared within an unnamed block_statement
. See 11.4.1(12).
Blocks have implementation defined names of the form Bnnn
where nnn is an integer.
41. The information returned by
Exception_Information
. See 11.4.1(13).
Exception_Information
returns a string in the following format:
Exception_Name: nnnnn Message: mmmmm PID: ppp Call stack traceback locations: 0xhhhh 0xhhhh 0xhhhh ... 0xhhh |
where
nnnn
is the fully qualified name of the exception in all upper
case letters. This line is always present.
mmmm
is the message (this line present only if message is non-null)
ppp
is the Process Id value as a decimal integer (this line is
present only if the Process Id is nonzero). Currently we are
not making use of this field.
The line terminator sequence at the end of each line, including
the last line is a single LF
character (16#0A#
).
42. Implementation-defined check names. See 11.5(27). The implementation defined check name Alignment_Check controls checking of address clause values for proper alignment (that is, the address supplied must be consistent with the alignment of the type).
In addition, a user program can add implementation-defined check names by means of the pragma Check_Name.
43. The interpretation of each aspect of representation. See 13.1(20). See separate section on data representations.
44. Any restrictions placed upon representation items. See 13.1(20). See separate section on data representations.
45. The meaning of Size
for indefinite subtypes. See
13.3(48).
Size for an indefinite subtype is the maximum possible size, except that
for the case of a subprogram parameter, the size of the parameter object
is the actual size.
46. The default external representation for a type tag. See 13.3(75). The default external representation for a type tag is the fully expanded name of the type in upper case letters.
47. What determines whether a compilation unit is the same in two different partitions. See 13.3(76). A compilation unit is the same in two different partitions if and only if it derives from the same source file.
48. Implementation-defined components. See 13.5.1(15). The only implementation defined component is the tag for a tagged type, which contains a pointer to the dispatching table.
49. If Word_Size
= Storage_Unit
, the default bit
ordering. See 13.5.3(5).
Word_Size
(32) is not the same as Storage_Unit
(8) for this
implementation, so no non-default bit ordering is supported. The default
bit ordering corresponds to the natural endianness of the target architecture.
50. The contents of the visible part of package System
and its language-defined children. See 13.7(2).
See the definition of these packages in files `system.ads' and
`s-stoele.ads'.
51. The contents of the visible part of package
System.Machine_Code
, and the meaning of
code_statements
. See 13.8(7).
See the definition and documentation in file `s-maccod.ads'.
52. The effect of unchecked conversion. See 13.9(11). Unchecked conversion between types of the same size results in an uninterpreted transmission of the bits from one type to the other. If the types are of unequal sizes, then in the case of discrete types, a shorter source is first zero or sign extended as necessary, and a shorter target is simply truncated on the left. For all non-discrete types, the source is first copied if necessary to ensure that the alignment requirements of the target are met, then a pointer is constructed to the source value, and the result is obtained by dereferencing this pointer after converting it to be a pointer to the target type. Unchecked conversions where the target subtype is an unconstrained array are not permitted. If the target alignment is greater than the source alignment, then a copy of the result is made with appropriate alignment
53. The semantics of operations on invalid representations. See 13.9.2(10-11). For assignments and other operations where the use of invalid values cannot result in erroneous behavior, the compiler ignores the possibility of invalid values. An exception is raised at the point where an invalid value would result in erroneous behavior. For example executing:
procedure invalidvals is X : Integer := -1; Y : Natural range 1 .. 10; for Y'Address use X'Address; Z : Natural range 1 .. 10; A : array (Natural range 1 .. 10) of Integer; begin Z := Y; -- no exception A (Z) := 3; -- exception raised; end; |
As indicated, an exception is raised on the array assignment, but not on the simple assignment of the invalid negative value from Y to Z.
53. The manner of choosing a storage pool for an access type
when Storage_Pool
is not specified for the type. See 13.11(17).
There are 3 different standard pools used by the compiler when
Storage_Pool
is not specified depending whether the type is local
to a subprogram or defined at the library level and whether
Storage_Size
is specified or not. See documentation in the runtime
library units System.Pool_Global
, System.Pool_Size
and
System.Pool_Local
in files `s-poosiz.ads',
`s-pooglo.ads' and `s-pooloc.ads' for full details on the
default pools used.
54. Whether or not the implementation provides user-accessible names for the standard pool type(s). See 13.11(17).
See documentation in the sources of the run time mentioned in paragraph
53 . All these pools are accessible by means of with
'ing
these units.
55. The meaning of Storage_Size
. See 13.11(18).
Storage_Size
is measured in storage units, and refers to the
total space available for an access type collection, or to the primary
stack space for a task.
56. Implementation-defined aspects of storage pools. See 13.11(22). See documentation in the sources of the run time mentioned in paragraph 53 for details on GNAT-defined aspects of storage pools.
57. The set of restrictions allowed in a pragma
Restrictions
. See 13.12(7).
See section 3. Standard and Implementation Defined Restrictions.
58. The consequences of violating limitations on
Restrictions
pragmas. See 13.12(9).
Restrictions that can be checked at compile time result in illegalities
if violated. Currently there are no other consequences of violating
restrictions.
59. The representation used by the Read
and
Write
attributes of elementary types in terms of stream
elements. See 13.13.2(9).
The representation is the in-memory representation of the base type of
the type, using the number of bits corresponding to the
type'Size
value, and the natural ordering of the machine.
60. The names and characteristics of the numeric subtypes
declared in the visible part of package Standard
. See A.1(3).
See items describing the integer and floating-point types supported.
61. The accuracy actually achieved by the elementary functions. See A.5.1(1). The elementary functions correspond to the functions available in the C library. Only fast math mode is implemented.
62. The sign of a zero result from some of the operators or
functions in Numerics.Generic_Elementary_Functions
, when
Float_Type'Signed_Zeros
is True
. See A.5.1(46).
The sign of zeroes follows the requirements of the IEEE 754 standard on
floating-point.
63. The value of
Numerics.Float_Random.Max_Image_Width
. See A.5.2(27).
Maximum image width is 6864, see library file `s-rannum.ads'.
64. The value of
Numerics.Discrete_Random.Max_Image_Width
. See A.5.2(27).
Maximum image width is 6864, see library file `s-rannum.ads'.
65. The algorithms for random number generation. See A.5.2(32). The algorithm is the Mersenne Twister, as documented in the source file `s-rannum.adb'. This version of the algorithm has a period of 2**19937-1.
66. The string representation of a random number generator's state. See A.5.2(38). The value returned by the Image function is the concatenation of the fixed-width decimal representations of the 624 32-bit integers of the state vector.
67. The minimum time interval between calls to the time-dependent Reset procedure that are guaranteed to initiate different random number sequences. See A.5.2(45). The minimum period between reset calls to guarantee distinct series of random numbers is one microsecond.
68. The values of the Model_Mantissa
,
Model_Emin
, Model_Epsilon
, Model
,
Safe_First
, and Safe_Last
attributes, if the Numerics
Annex is not supported. See A.5.3(72).
Run the compiler with `-gnatS' to produce a listing of package
Standard
, has the values of all numeric attributes.
69. Any implementation-defined characteristics of the input-output packages. See A.7(14). There are no special implementation defined characteristics for these packages.
70. The value of Buffer_Size
in Storage_IO
. See
A.9(10).
All type representations are contiguous, and the Buffer_Size
is
the value of type'Size
rounded up to the next storage unit
boundary.
71. External files for standard input, standard output, and standard error See A.10(5). These files are mapped onto the files provided by the C streams libraries. See source file `i-cstrea.ads' for further details.
72. The accuracy of the value produced by Put
. See
A.10.9(36).
If more digits are requested in the output than are represented by the
precision of the value, zeroes are output in the corresponding least
significant digit positions.
73. The meaning of Argument_Count
, Argument
, and
Command_Name
. See A.15(1).
These are mapped onto the argv
and argc
parameters of the
main program in the natural manner.
74. The interpretation of the Form
parameter in procedure
Create_Directory
. See A.16(56).
The Form
parameter is not used.
75. The interpretation of the Form
parameter in procedure
Create_Path
. See A.16(60).
The Form
parameter is not used.
76. The interpretation of the Form
parameter in procedure
Copy_File
. See A.16(68).
The Form
parameter is case-insensitive.
Two fields are recognized in the Form
parameter:
preserve=<value>
mode=<value>
<value> starts immediately after the character '=' and ends with the character immediately preceding the next comma (',') or with the last character of the parameter.
The only possible values for preserve= are:
no_attributes
all_attributes
timestamps
The only possible values for mode= are:
copy
overwrite
append
If the Form parameter includes one or both of the fields and the value or values are incorrect, Copy_file fails with Use_Error.
Examples of correct Forms:
Form => "preserve=no_attributes,mode=overwrite" (the default) Form => "mode=append" Form => "mode=copy, preserve=all_attributes" |
Examples of incorrect Forms
Form => "preserve=junk" Form => "mode=internal, preserve=timestamps" |
77. Implementation-defined convention names. See B.1(11). The following convention names are supported
Ada
Ada_Pass_By_Copy
Ada_Pass_By_Reference
Assembler
Asm
Assembly
C
C_Pass_By_Copy
COBOL
C_Plus_Plus (or CPP)
Default
External
Fortran
Intrinsic
Import
with convention Intrinsic, see
separate section on Intrinsic Subprograms.
Stdcall
DLL
Win32
Stubbed
Program_Error
exception. If a
pragma Import
specifies convention stubbed
then no body need
be present at all. This convention is useful during development for the
inclusion of subprograms whose body has not yet been written.
78. The meaning of link names. See B.1(36). Link names are the actual names used by the linker.
79. The manner of choosing link names when neither the link name nor the address of an imported or exported entity is specified. See B.1(36). The default linker name is that which would be assigned by the relevant external language, interpreting the Ada name as being in all lower case letters.
80. The effect of pragma Linker_Options
. See B.1(37).
The string passed to Linker_Options
is presented uninterpreted as
an argument to the link command, unless it contains ASCII.NUL characters.
NUL characters if they appear act as argument separators, so for example
pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef"); |
causes two separate arguments -labc
and -ldef
to be passed to the
linker. The order of linker options is preserved for a given unit. The final
list of options passed to the linker is in reverse order of the elaboration
order. For example, linker options for a body always appear before the options
from the corresponding package spec.
81. The contents of the visible part of package
Interfaces
and its language-defined descendants. See B.2(1).
See files with prefix `i-' in the distributed library.
82. Implementation-defined children of package
Interfaces
. The contents of the visible part of package
Interfaces
. See B.2(11).
See files with prefix `i-' in the distributed library.
83. The types Floating
, Long_Floating
,
Binary
, Long_Binary
, Decimal_ Element
, and
COBOL_Character
; and the initialization of the variables
Ada_To_COBOL
and COBOL_To_Ada
, in
Interfaces.COBOL
. See B.4(50).
Floating
Long_Floating
Binary
Long_Binary
Decimal_Element
COBOL_Character
For initialization, see the file `i-cobol.ads' in the distributed library.
84. Support for access to machine instructions. See C.1(1). See documentation in file `s-maccod.ads' in the distributed library.
85. Implementation-defined aspects of access to machine operations. See C.1(9). See documentation in file `s-maccod.ads' in the distributed library.
86. Implementation-defined aspects of interrupts. See C.3(2).
Interrupts are mapped to signals or conditions as appropriate. See
definition of unit
Ada.Interrupt_Names
in source file `a-intnam.ads' for details
on the interrupts supported on a particular target.
87. Implementation-defined aspects of pre-elaboration. See C.4(13). GNAT does not permit a partition to be restarted without reloading, except under control of the debugger.
88. The semantics of pragma Discard_Names
. See C.5(7).
Pragma Discard_Names
causes names of enumeration literals to
be suppressed. In the presence of this pragma, the Image attribute
provides the image of the Pos of the literal, and Value accepts
Pos values.
89. The result of the Task_Identification.Image
attribute. See C.7.1(7).
The result of this attribute is a string that identifies
the object or component that denotes a given task. If a variable Var
has a task type, the image for this task will have the form Var_XXXXXXXX
,
where the suffix
is the hexadecimal representation of the virtual address of the corresponding
task control block. If the variable is an array of tasks, the image of each
task will have the form of an indexed component indicating the position of a
given task in the array, e.g. Group(5)_XXXXXXX
. If the task is a
component of a record, the image of the task will have the form of a selected
component. These rules are fully recursive, so that the image of a task that
is a subcomponent of a composite object corresponds to the expression that
designates this task.
If a task is created by an allocator, its image depends on the context. If the
allocator is part of an object declaration, the rules described above are used
to construct its image, and this image is not affected by subsequent
assignments. If the allocator appears within an expression, the image
includes only the name of the task type.
If the configuration pragma Discard_Names is present, or if the restriction
No_Implicit_Heap_Allocation is in effect, the image reduces to
the numeric suffix, that is to say the hexadecimal representation of the
virtual address of the control block of the task.
90. The value of Current_Task
when in a protected entry
or interrupt handler. See C.7.1(17).
Protected entries or interrupt handlers can be executed by any
convenient thread, so the value of Current_Task
is undefined.
91. The effect of calling Current_Task
from an entry
body or interrupt handler. See C.7.1(19).
The effect of calling Current_Task
from an entry body or
interrupt handler is to return the identification of the task currently
executing the code.
92. Implementation-defined aspects of
Task_Attributes
. See C.7.2(19).
There are no implementation-defined aspects of Task_Attributes
.
93. Values of all Metrics
. See D(2).
The metrics information for GNAT depends on the performance of the
underlying operating system. The sources of the run-time for tasking
implementation, together with the output from `-gnatG' can be
used to determine the exact sequence of operating systems calls made
to implement various tasking constructs. Together with appropriate
information on the performance of the underlying operating system,
on the exact target in use, this information can be used to determine
the required metrics.
94. The declarations of Any_Priority
and
Priority
. See D.1(11).
See declarations in file `system.ads'.
95. Implementation-defined execution resources. See D.1(15). There are no implementation-defined execution resources.
96. Whether, on a multiprocessor, a task that is waiting for access to a protected object keeps its processor busy. See D.2.1(3). On a multi-processor, a task that is waiting for access to a protected object does not keep its processor busy.
97. The affect of implementation defined execution resources on task dispatching. See D.2.1(9). Tasks map to threads in the threads package used by GNAT. Where possible and appropriate, these threads correspond to native threads of the underlying operating system.
98. Implementation-defined policy_identifiers
allowed
in a pragma Task_Dispatching_Policy
. See D.2.2(3).
There are no implementation-defined policy-identifiers allowed in this
pragma.
99. Implementation-defined aspects of priority inversion. See D.2.2(16). Execution of a task cannot be preempted by the implementation processing of delay expirations for lower priority tasks.
100. Implementation-defined task dispatching. See D.2.2(18). The policy is the same as that of the underlying threads implementation.
101. Implementation-defined policy_identifiers
allowed
in a pragma Locking_Policy
. See D.3(4).
The two implementation defined policies permitted in GNAT are
Inheritance_Locking
and Conccurent_Readers_Locking
. On
targets that support the Inheritance_Locking
policy, locking is
implemented by inheritance, i.e. the task owning the lock operates
at a priority equal to the highest priority of any task currently
requesting the lock. On targets that support the
Conccurent_Readers_Locking
policy, locking is implemented with a
read/write lock allowing multiple propected object functions to enter
concurrently.
102. Default ceiling priorities. See D.3(10).
The ceiling priority of protected objects of the type
System.Interrupt_Priority'Last
as described in the Ada
Reference Manual D.3(10),
103. The ceiling of any protected object used internally by
the implementation. See D.3(16).
The ceiling priority of internal protected objects is
System.Priority'Last
.
104. Implementation-defined queuing policies. See D.4(1). There are no implementation-defined queuing policies.
105. On a multiprocessor, any conditions that cause the completion of an aborted construct to be delayed later than what is specified for a single processor. See D.6(3). The semantics for abort on a multi-processor is the same as on a single processor, there are no further delays.
106. Any operations that implicitly require heap storage allocation. See D.7(8). The only operation that implicitly requires heap storage allocation is task creation.
107. Implementation-defined aspects of pragma
Restrictions
. See D.7(20).
There are no such implementation-defined aspects.
108. Implementation-defined aspects of package
Real_Time
. See D.8(17).
There are no implementation defined aspects of package Real_Time
.
109. Implementation-defined aspects of
delay_statements
. See D.9(8).
Any difference greater than one microsecond will cause the task to be
delayed (see D.9(7)).
110. The upper bound on the duration of interrupt blocking caused by the implementation. See D.12(5). The upper bound is determined by the underlying operating system. In no cases is it more than 10 milliseconds.
111. The means for creating and executing distributed programs. See E(5). The GLADE package provides a utility GNATDIST for creating and executing distributed programs. See the GLADE reference manual for further details.
112. Any events that can result in a partition becoming inaccessible. See E.1(7). See the GLADE reference manual for full details on such events.
113. The scheduling policies, treatment of priorities, and management of shared resources between partitions in certain cases. See E.1(11). See the GLADE reference manual for full details on these aspects of multi-partition execution.
114. Events that cause the version of a compilation unit to change. See E.3(5). Editing the source file of a compilation unit, or the source files of any units on which it is dependent in a significant way cause the version to change. No other actions cause the version number to change. All changes are significant except those which affect only layout, capitalization or comments.
115. Whether the execution of the remote subprogram is immediately aborted as a result of cancellation. See E.4(13). See the GLADE reference manual for details on the effect of abort in a distributed application.
116. Implementation-defined aspects of the PCS. See E.5(25). See the GLADE reference manual for a full description of all implementation defined aspects of the PCS.
117. Implementation-defined interfaces in the PCS. See E.5(26). See the GLADE reference manual for a full description of all implementation defined interfaces.
118. The values of named numbers in the package
Decimal
. See F.2(7).
Max_Scale
Min_Scale
Min_Delta
Max_Delta
Max_Decimal_Digits
119. The value of Max_Picture_Length
in the package
Text_IO.Editing
. See F.3.3(16).
64
120. The value of Max_Picture_Length
in the package
Wide_Text_IO.Editing
. See F.3.4(5).
64
121. The accuracy actually achieved by the complex elementary functions and by other complex arithmetic operations. See G.1(1). Standard library functions are used for the complex arithmetic operations. Only fast math mode is currently supported.
122. The sign of a zero result (or a component thereof) from
any operator or function in Numerics.Generic_Complex_Types
, when
Real'Signed_Zeros
is True. See G.1.1(53).
The signs of zero values are as recommended by the relevant
implementation advice.
123. The sign of a zero result (or a component thereof) from
any operator or function in
Numerics.Generic_Complex_Elementary_Functions
, when
Real'Signed_Zeros
is True
. See G.1.2(45).
The signs of zero values are as recommended by the relevant
implementation advice.
124. Whether the strict mode or the relaxed mode is the default. See G.2(2). The strict mode is the default. There is no separate relaxed mode. GNAT provides a highly efficient implementation of strict mode.
125. The result interval in certain cases of fixed-to-float conversion. See G.2.1(10). For cases where the result interval is implementation dependent, the accuracy is that provided by performing all operations in 64-bit IEEE floating-point format.
126. The result of a floating point arithmetic operation in
overflow situations, when the Machine_Overflows
attribute of the
result type is False
. See G.2.1(13).
Infinite and NaN values are produced as dictated by the IEEE
floating-point standard.
Note that on machines that are not fully compliant with the IEEE floating-point standard, such as Alpha, the `-mieee' compiler flag must be used for achieving IEEE conforming behavior (although at the cost of a significant performance penalty), so infinite and NaN values are properly generated.
127. The result interval for division (or exponentiation by a negative exponent), when the floating point hardware implements division as multiplication by a reciprocal. See G.2.1(16). Not relevant, division is IEEE exact.
128. The definition of close result set, which determines the accuracy of certain fixed point multiplications and divisions. See G.2.3(5). Operations in the close result set are performed using IEEE long format floating-point arithmetic. The input operands are converted to floating-point, the operation is done in floating-point, and the result is converted to the target type.
129. Conditions on a universal_real
operand of a fixed
point multiplication or division for which the result shall be in the
perfect result set. See G.2.3(22).
The result is only defined to be in the perfect result set if the result
can be computed by a single scaling operation involving a scale factor
representable in 64-bits.
130. The result of a fixed point arithmetic operation in
overflow situations, when the Machine_Overflows
attribute of the
result type is False
. See G.2.3(27).
Not relevant, Machine_Overflows
is True
for fixed-point
types.
131. The result of an elementary function reference in
overflow situations, when the Machine_Overflows
attribute of the
result type is False
. See G.2.4(4).
IEEE infinite and Nan values are produced as appropriate.
132. The value of the angle threshold, within which certain elementary functions, complex arithmetic operations, and complex elementary functions yield results conforming to a maximum relative error bound. See G.2.4(10). Information on this subject is not yet available.
133. The accuracy of certain elementary functions for parameters beyond the angle threshold. See G.2.4(10). Information on this subject is not yet available.
134. The result of a complex arithmetic operation or complex
elementary function reference in overflow situations, when the
Machine_Overflows
attribute of the corresponding real type is
False
. See G.2.6(5).
IEEE infinite and Nan values are produced as appropriate.
135. The accuracy of certain complex arithmetic operations and certain complex elementary functions for parameters (or components thereof) beyond the angle threshold. See G.2.6(8). Information on those subjects is not yet available.
136. Information regarding bounded errors and erroneous execution. See H.2(1). Information on this subject is not yet available.
137. Implementation-defined aspects of pragma
Inspection_Point
. See H.3.2(8).
Pragma Inspection_Point
ensures that the variable is live and can
be examined by the debugger at the inspection point.
138. Implementation-defined aspects of pragma
Restrictions
. See H.4(25).
There are no implementation-defined aspects of pragma Restrictions
. The
use of pragma Restrictions [No_Exceptions]
has no effect on the
generated code. Checks must suppressed by use of pragma Suppress
.
139. Any restrictions on pragma Restrictions
. See
H.4(27).
There are no restrictions on pragma Restrictions
.
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