1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1996-2008, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 with Atree; use Atree;
27 with Einfo; use Einfo;
28 with Errout; use Errout;
29 with Namet; use Namet;
30 with Nlists; use Nlists;
32 with Sem_Aux; use Sem_Aux;
33 with Sem_Util; use Sem_Util;
34 with Sinfo; use Sinfo;
35 with Snames; use Snames;
36 with Stand; use Stand;
37 with Targparm; use Targparm;
39 package body Sem_Mech is
41 -------------------------
42 -- Set_Mechanism_Value --
43 -------------------------
45 procedure Set_Mechanism_Value (Ent : Entity_Id; Mech_Name : Node_Id) is
50 -- Signal bad descriptor class name
52 procedure Bad_Mechanism;
53 -- Signal bad mechanism name
55 procedure Bad_Class is
57 Error_Msg_N ("unrecognized descriptor class name", Class);
60 procedure Bad_Mechanism is
62 Error_Msg_N ("unrecognized mechanism name", Mech_Name);
65 -- Start of processing for Set_Mechanism_Value
68 if Mechanism (Ent) /= Default_Mechanism then
70 ("mechanism for & has already been set", Mech_Name, Ent);
73 -- MECHANISM_NAME ::= value | reference | descriptor | short_descriptor
75 if Nkind (Mech_Name) = N_Identifier then
76 if Chars (Mech_Name) = Name_Value then
77 Set_Mechanism_With_Checks (Ent, By_Copy, Mech_Name);
80 elsif Chars (Mech_Name) = Name_Reference then
81 Set_Mechanism_With_Checks (Ent, By_Reference, Mech_Name);
84 elsif Chars (Mech_Name) = Name_Descriptor then
85 Check_VMS (Mech_Name);
86 Set_Mechanism_With_Checks (Ent, By_Descriptor, Mech_Name);
89 elsif Chars (Mech_Name) = Name_Short_Descriptor then
90 Check_VMS (Mech_Name);
91 Set_Mechanism_With_Checks (Ent, By_Short_Descriptor, Mech_Name);
94 elsif Chars (Mech_Name) = Name_Copy then
96 ("bad mechanism name, Value assumed", Mech_Name);
97 Set_Mechanism (Ent, By_Copy);
104 -- MECHANISM_NAME ::= descriptor (CLASS_NAME) |
105 -- short_descriptor (CLASS_NAME)
106 -- CLASS_NAME ::= ubs | ubsb | uba | s | sb | a | nca
108 -- Note: this form is parsed as an indexed component
110 elsif Nkind (Mech_Name) = N_Indexed_Component then
111 Class := First (Expressions (Mech_Name));
113 if Nkind (Prefix (Mech_Name)) /= N_Identifier
114 or else not (Chars (Prefix (Mech_Name)) = Name_Descriptor or else
115 Chars (Prefix (Mech_Name)) = Name_Short_Descriptor)
116 or else Present (Next (Class))
122 -- MECHANISM_NAME ::= descriptor (Class => CLASS_NAME) |
123 -- short_descriptor (Class => CLASS_NAME)
124 -- CLASS_NAME ::= ubs | ubsb | uba | s | sb | a | nca
126 -- Note: this form is parsed as a function call
128 elsif Nkind (Mech_Name) = N_Function_Call then
130 Param := First (Parameter_Associations (Mech_Name));
132 if Nkind (Name (Mech_Name)) /= N_Identifier
133 or else not (Chars (Name (Mech_Name)) = Name_Descriptor or else
134 Chars (Name (Mech_Name)) = Name_Short_Descriptor)
135 or else Present (Next (Param))
136 or else No (Selector_Name (Param))
137 or else Chars (Selector_Name (Param)) /= Name_Class
142 Class := Explicit_Actual_Parameter (Param);
150 -- Fall through here with Class set to descriptor class name
152 Check_VMS (Mech_Name);
154 if Nkind (Class) /= N_Identifier then
158 elsif Chars (Name (Mech_Name)) = Name_Descriptor
159 and then Chars (Class) = Name_UBS
161 Set_Mechanism_With_Checks (Ent, By_Descriptor_UBS, Mech_Name);
163 elsif Chars (Name (Mech_Name)) = Name_Descriptor
164 and then Chars (Class) = Name_UBSB
166 Set_Mechanism_With_Checks (Ent, By_Descriptor_UBSB, Mech_Name);
168 elsif Chars (Name (Mech_Name)) = Name_Descriptor
169 and then Chars (Class) = Name_UBA
171 Set_Mechanism_With_Checks (Ent, By_Descriptor_UBA, Mech_Name);
173 elsif Chars (Name (Mech_Name)) = Name_Descriptor
174 and then Chars (Class) = Name_S
176 Set_Mechanism_With_Checks (Ent, By_Descriptor_S, Mech_Name);
178 elsif Chars (Name (Mech_Name)) = Name_Descriptor
179 and then Chars (Class) = Name_SB
181 Set_Mechanism_With_Checks (Ent, By_Descriptor_SB, Mech_Name);
183 elsif Chars (Name (Mech_Name)) = Name_Descriptor
184 and then Chars (Class) = Name_A
186 Set_Mechanism_With_Checks (Ent, By_Descriptor_A, Mech_Name);
188 elsif Chars (Name (Mech_Name)) = Name_Descriptor
189 and then Chars (Class) = Name_NCA
191 Set_Mechanism_With_Checks (Ent, By_Descriptor_NCA, Mech_Name);
193 elsif Chars (Name (Mech_Name)) = Name_Short_Descriptor
194 and then Chars (Class) = Name_UBS
196 Set_Mechanism_With_Checks (Ent, By_Short_Descriptor_UBS, Mech_Name);
198 elsif Chars (Name (Mech_Name)) = Name_Short_Descriptor
199 and then Chars (Class) = Name_UBSB
201 Set_Mechanism_With_Checks (Ent, By_Short_Descriptor_UBSB, Mech_Name);
203 elsif Chars (Name (Mech_Name)) = Name_Short_Descriptor
204 and then Chars (Class) = Name_UBA
206 Set_Mechanism_With_Checks (Ent, By_Short_Descriptor_UBA, Mech_Name);
208 elsif Chars (Name (Mech_Name)) = Name_Short_Descriptor
209 and then Chars (Class) = Name_S
211 Set_Mechanism_With_Checks (Ent, By_Short_Descriptor_S, Mech_Name);
213 elsif Chars (Name (Mech_Name)) = Name_Short_Descriptor
214 and then Chars (Class) = Name_SB
216 Set_Mechanism_With_Checks (Ent, By_Short_Descriptor_SB, Mech_Name);
218 elsif Chars (Name (Mech_Name)) = Name_Short_Descriptor
219 and then Chars (Class) = Name_A
221 Set_Mechanism_With_Checks (Ent, By_Short_Descriptor_A, Mech_Name);
223 elsif Chars (Name (Mech_Name)) = Name_Short_Descriptor
224 and then Chars (Class) = Name_NCA
226 Set_Mechanism_With_Checks (Ent, By_Short_Descriptor_NCA, Mech_Name);
232 end Set_Mechanism_Value;
234 -------------------------------
235 -- Set_Mechanism_With_Checks --
236 -------------------------------
238 procedure Set_Mechanism_With_Checks
240 Mech : Mechanism_Type;
244 -- Right now we only do some checks for functions returning arguments
245 -- by descriptor. Probably mode checks need to be added here ???
247 if Mech in Descriptor_Codes and then not Is_Formal (Ent) then
248 if Is_Record_Type (Etype (Ent)) then
249 Error_Msg_N ("?records cannot be returned by Descriptor", Enod);
254 -- If we fall through, all checks have passed
256 Set_Mechanism (Ent, Mech);
257 end Set_Mechanism_With_Checks;
263 procedure Set_Mechanisms (E : Entity_Id) is
268 -- Skip this processing if inside a generic template. Not only is
269 -- it unnecessary (since neither extra formals nor mechanisms are
270 -- relevant for the template itself), but at least at the moment,
271 -- procedures get frozen early inside a template so attempting to
272 -- look at the formal types does not work too well if they are
273 -- private types that have not been frozen yet.
275 if Inside_A_Generic then
279 -- Loop through formals
281 Formal := First_Formal (E);
282 while Present (Formal) loop
284 if Mechanism (Formal) = Default_Mechanism then
285 Typ := Underlying_Type (Etype (Formal));
287 -- If there is no underlying type, then skip this processing and
288 -- leave the convention set to Default_Mechanism. It seems odd
289 -- that there should ever be such cases but there are (see
290 -- comments for filed regression tests 1418-001 and 1912-009) ???
296 case Convention (E) is
302 -- Note: all RM defined conventions are treated the same
303 -- from the point of view of parameter passing mechanism
305 when Convention_Ada |
306 Convention_Intrinsic |
308 Convention_Protected |
309 Convention_Stubbed =>
311 -- By reference types are passed by reference (RM 6.2(4))
313 if Is_By_Reference_Type (Typ) then
314 Set_Mechanism (Formal, By_Reference);
316 -- By copy types are passed by copy (RM 6.2(3))
318 elsif Is_By_Copy_Type (Typ) then
319 Set_Mechanism (Formal, By_Copy);
321 -- All other types we leave the Default_Mechanism set, so
322 -- that the backend can choose the appropriate method.
332 -- Note: Assembler, C++, Java, Stdcall also use C conventions
334 when Convention_Assembler |
339 Convention_Stdcall =>
341 -- The following values are passed by copy
343 -- IN Scalar parameters (RM B.3(66))
344 -- IN parameters of access types (RM B.3(67))
345 -- Access parameters (RM B.3(68))
346 -- Access to subprogram types (RM B.3(71))
348 -- Note: in the case of access parameters, it is the
349 -- pointer that is passed by value. In GNAT access
350 -- parameters are treated as IN parameters of an
351 -- anonymous access type, so this falls out free.
353 -- The bottom line is that all IN elementary types
354 -- are passed by copy in GNAT.
356 if Is_Elementary_Type (Typ) then
357 if Ekind (Formal) = E_In_Parameter then
358 Set_Mechanism (Formal, By_Copy);
360 -- OUT and IN OUT parameters of elementary types are
361 -- passed by reference (RM B.3(68)). Note that we are
362 -- not following the advice to pass the address of a
363 -- copy to preserve by copy semantics.
366 Set_Mechanism (Formal, By_Reference);
369 -- Records are normally passed by reference (RM B.3(69)).
370 -- However, this can be overridden by the use of the
371 -- C_Pass_By_Copy pragma or C_Pass_By_Copy convention.
373 elsif Is_Record_Type (Typ) then
375 -- If the record is not convention C, then we always
376 -- pass by reference, C_Pass_By_Copy does not apply.
378 if Convention (Typ) /= Convention_C then
379 Set_Mechanism (Formal, By_Reference);
381 -- If convention C_Pass_By_Copy was specified for
382 -- the record type, then we pass by copy.
384 elsif C_Pass_By_Copy (Typ) then
385 Set_Mechanism (Formal, By_Copy);
387 -- Otherwise, for a C convention record, we set the
388 -- convention in accordance with a possible use of
389 -- the C_Pass_By_Copy pragma. Note that the value of
390 -- Default_C_Record_Mechanism in the absence of such
391 -- a pragma is By_Reference.
394 Set_Mechanism (Formal, Default_C_Record_Mechanism);
397 -- Array types are passed by reference (B.3 (71))
399 elsif Is_Array_Type (Typ) then
400 Set_Mechanism (Formal, By_Reference);
402 -- For all other types, use Default_Mechanism mechanism
412 when Convention_COBOL =>
414 -- Access parameters (which in GNAT look like IN parameters
415 -- of an access type) are passed by copy (RM B.4(96)) as
416 -- are all other IN parameters of scalar type (RM B.4(97)).
418 -- For now we pass these parameters by reference as well.
419 -- The RM specifies the intent BY_CONTENT, but gigi does
420 -- not currently transform By_Copy properly. If we pass by
421 -- reference, it will be imperative to introduce copies ???
423 if Is_Elementary_Type (Typ)
424 and then Ekind (Formal) = E_In_Parameter
426 Set_Mechanism (Formal, By_Reference);
428 -- All other parameters (i.e. all non-scalar types, and
429 -- all OUT or IN OUT parameters) are passed by reference.
430 -- Note that at the moment we are not bothering to make
431 -- copies of scalar types as recommended in the RM.
434 Set_Mechanism (Formal, By_Reference);
441 when Convention_Fortran =>
443 -- In OpenVMS, pass a character of array of character
444 -- value using Descriptor(S).
447 and then (Root_Type (Typ) = Standard_Character
451 Root_Type (Component_Type (Typ)) =
454 Set_Mechanism (Formal, By_Descriptor_S);
456 -- Access types are passed by default (presumably this
457 -- will mean they are passed by copy)
459 elsif Is_Access_Type (Typ) then
462 -- For now, we pass all other parameters by reference.
463 -- It is not clear that this is right in the long run,
464 -- but it seems to correspond to what gnu f77 wants.
467 Set_Mechanism (Formal, By_Reference);
473 <<Skip_Formal>> -- remove this when problem above is fixed ???
475 Next_Formal (Formal);
478 -- Note: there is nothing we need to do for the return type here.
479 -- We deal with returning by reference in the Ada sense, by use of
480 -- the flag By_Ref, rather than by messing with mechanisms.
482 -- A mechanism of Reference for the return means that an extra
483 -- parameter must be provided for the return value (that is the
484 -- DEC meaning of the pragma), and is unrelated to the Ada notion
485 -- of return by reference.
487 -- Note: there was originally code here to set the mechanism to
488 -- By_Reference for types that are "by reference" in the Ada sense,
489 -- but, in accordance with the discussion above, this is wrong, and
490 -- the code was removed.