c-pragma.c revision 90075 
1/* Handle #pragma, system V.4 style.  Supports #pragma weak and #pragma pack.
2   Copyright (C) 1992, 1997, 1998, 1999, 2000, 2001
3   Free Software Foundation, Inc.
4
5This file is part of GCC.
6
7GCC is free software; you can redistribute it and/or modify it under
8the terms of the GNU General Public License as published by the Free
9Software Foundation; either version 2, or (at your option) any later
10version.
11
12GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13WARRANTY; without even the implied warranty of MERCHANTABILITY or
14FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
15for more details.
16
17You should have received a copy of the GNU General Public License
18along with GCC; see the file COPYING.  If not, write to the Free
19Software Foundation, 59 Temple Place - Suite 330, Boston, MA
2002111-1307, USA.  */
21
22#include "config.h"
23#include "system.h"
24#include "rtl.h"
25#include "tree.h"
26#include "function.h"
27#include "cpplib.h"
28#include "c-pragma.h"
29#include "flags.h"
30#include "toplev.h"
31#include "ggc.h"
32#include "c-lex.h"
33#include "output.h"
34#include "tm_p.h"
35
36#define GCC_BAD(msgid) do { warning (msgid); return; } while (0)
37#define GCC_BAD2(msgid, arg) do { warning (msgid, arg); return; } while (0)
38
39#ifdef HANDLE_PRAGMA_PACK
40static void handle_pragma_pack PARAMS ((cpp_reader *));
41
42#ifdef HANDLE_PRAGMA_PACK_PUSH_POP
43typedef struct align_stack
44{
45  int                  alignment;
46  unsigned int         num_pushes;
47  tree                 id;
48  struct align_stack * prev;
49} align_stack;
50
51static struct align_stack * alignment_stack = NULL;
52
53/* If we have a "global" #pragma pack(<n>) in effect when the first
54   #pragma pack(push,<n>) is encountered, this stores the value of
55   maximum_field_alignment in effect.  When the final pop_alignment()
56   happens, we restore the value to this, not to a value of 0 for
57   maximum_field_alignment.  Value is in bits.  */
58static int  default_alignment;
59#define SET_GLOBAL_ALIGNMENT(ALIGN) \
60(default_alignment = maximum_field_alignment = (ALIGN))
61
62static void push_alignment PARAMS ((int, tree));
63static void pop_alignment  PARAMS ((tree));
64static void mark_align_stack PARAMS ((void *));
65
66/* Push an alignment value onto the stack.  */
67static void
68push_alignment (alignment, id)
69     int alignment;
70     tree id;
71{
72
73  if (alignment_stack == NULL
74      || alignment_stack->alignment != alignment
75      || id != NULL_TREE)
76    {
77      align_stack * entry;
78
79      entry = (align_stack *) xmalloc (sizeof (* entry));
80
81      entry->alignment  = alignment;
82      entry->num_pushes = 1;
83      entry->id         = id;
84      entry->prev       = alignment_stack;
85
86      /* The current value of maximum_field_alignment is not necessarily
87	 0 since there may be a #pragma pack(<n>) in effect; remember it
88	 so that we can restore it after the final #pragma pop().  */
89      if (alignment_stack == NULL)
90	default_alignment = maximum_field_alignment;
91
92      alignment_stack = entry;
93
94      maximum_field_alignment = alignment;
95    }
96  else
97    alignment_stack->num_pushes ++;
98}
99
100/* Undo a push of an alignment onto the stack.  */
101static void
102pop_alignment (id)
103     tree id;
104{
105  align_stack * entry;
106
107  if (alignment_stack == NULL)
108    {
109      warning ("\
110#pragma pack (pop) encountered without matching #pragma pack (push, <n>)"
111	       );
112      return;
113    }
114
115  /* If we got an identifier, strip away everything above the target
116     entry so that the next step will restore the state just below it.  */
117  if (id)
118    {
119      for (entry = alignment_stack; entry; entry = entry->prev)
120	if (entry->id == id)
121	  {
122	    entry->num_pushes = 1;
123	    alignment_stack = entry;
124	    break;
125	  }
126      if (entry == NULL)
127	warning ("\
128#pragma pack(pop, %s) encountered without matching #pragma pack(push, %s, <n>)"
129		 , IDENTIFIER_POINTER (id), IDENTIFIER_POINTER (id));
130    }
131
132  if (-- alignment_stack->num_pushes == 0)
133    {
134      entry = alignment_stack->prev;
135
136      if (entry == NULL)
137	maximum_field_alignment = default_alignment;
138      else
139	maximum_field_alignment = entry->alignment;
140
141      free (alignment_stack);
142
143      alignment_stack = entry;
144    }
145}
146
147static void
148mark_align_stack (p)
149    void *p;
150{
151  align_stack *a = *(align_stack **) p;
152
153  while (a)
154    {
155      ggc_mark_tree (a->id);
156      a = a->prev;
157    }
158}
159#else  /* not HANDLE_PRAGMA_PACK_PUSH_POP */
160#define SET_GLOBAL_ALIGNMENT(ALIGN) (maximum_field_alignment = (ALIGN))
161#define push_alignment(ID, N) \
162    GCC_BAD("#pragma pack(push[, id], <n>) is not supported on this target")
163#define pop_alignment(ID) \
164    GCC_BAD("#pragma pack(pop[, id], <n>) is not supported on this target")
165#endif /* HANDLE_PRAGMA_PACK_PUSH_POP */
166
167/* #pragma pack ()
168   #pragma pack (N)
169
170   #pragma pack (push, N)
171   #pragma pack (push, ID, N)
172   #pragma pack (pop)
173   #pragma pack (pop, ID) */
174static void
175handle_pragma_pack (dummy)
176     cpp_reader *dummy ATTRIBUTE_UNUSED;
177{
178  tree x, id = 0;
179  int align = -1;
180  enum cpp_ttype token;
181  enum { set, push, pop } action;
182
183  if (c_lex (&x) != CPP_OPEN_PAREN)
184    GCC_BAD ("missing '(' after '#pragma pack' - ignored");
185
186  token = c_lex (&x);
187  if (token == CPP_CLOSE_PAREN)
188    {
189      action = set;
190      align = 0;
191    }
192  else if (token == CPP_NUMBER)
193    {
194      align = TREE_INT_CST_LOW (x);
195      action = set;
196      if (c_lex (&x) != CPP_CLOSE_PAREN)
197	GCC_BAD ("malformed '#pragma pack' - ignored");
198    }
199  else if (token == CPP_NAME)
200    {
201#define GCC_BAD_ACTION do { if (action == push) \
202	  GCC_BAD ("malformed '#pragma pack(push[, id], <n>)' - ignored"); \
203	else \
204	  GCC_BAD ("malformed '#pragma pack(pop[, id])' - ignored"); \
205	} while (0)
206
207      const char *op = IDENTIFIER_POINTER (x);
208      if (!strcmp (op, "push"))
209	action = push;
210      else if (!strcmp (op, "pop"))
211	action = pop;
212      else
213	GCC_BAD2 ("unknown action '%s' for '#pragma pack' - ignored", op);
214
215      token = c_lex (&x);
216      if (token != CPP_COMMA && action == push)
217	GCC_BAD_ACTION;
218
219      if (token == CPP_COMMA)
220	{
221	  token = c_lex (&x);
222	  if (token == CPP_NAME)
223	    {
224	      id = x;
225	      if (action == push && c_lex (&x) != CPP_COMMA)
226		GCC_BAD_ACTION;
227	      token = c_lex (&x);
228	    }
229
230	  if (action == push)
231	    {
232	      if (token == CPP_NUMBER)
233		{
234		  align = TREE_INT_CST_LOW (x);
235		  token = c_lex (&x);
236		}
237	      else
238		GCC_BAD_ACTION;
239	    }
240	}
241
242      if (token != CPP_CLOSE_PAREN)
243	GCC_BAD_ACTION;
244#undef GCC_BAD_ACTION
245    }
246  else
247    GCC_BAD ("malformed '#pragma pack' - ignored");
248
249  if (c_lex (&x) != CPP_EOF)
250    warning ("junk at end of '#pragma pack'");
251
252  if (action != pop)
253    switch (align)
254      {
255      case 0:
256      case 1:
257      case 2:
258      case 4:
259      case 8:
260      case 16:
261	align *= BITS_PER_UNIT;
262	break;
263      default:
264	GCC_BAD2 ("alignment must be a small power of two, not %d", align);
265      }
266
267  switch (action)
268    {
269    case set:   SET_GLOBAL_ALIGNMENT (align);  break;
270    case push:  push_alignment (align, id);    break;
271    case pop:   pop_alignment (id);            break;
272    }
273}
274#endif  /* HANDLE_PRAGMA_PACK */
275
276#ifdef HANDLE_PRAGMA_WEAK
277static void handle_pragma_weak PARAMS ((cpp_reader *));
278
279/* #pragma weak name [= value] */
280static void
281handle_pragma_weak (dummy)
282     cpp_reader *dummy ATTRIBUTE_UNUSED;
283{
284  tree name, value, x;
285  enum cpp_ttype t;
286
287  value = 0;
288
289  if (c_lex (&name) != CPP_NAME)
290    GCC_BAD ("malformed #pragma weak, ignored");
291  t = c_lex (&x);
292  if (t == CPP_EQ)
293    {
294      if (c_lex (&value) != CPP_NAME)
295	GCC_BAD ("malformed #pragma weak, ignored");
296      t = c_lex (&x);
297    }
298  if (t != CPP_EOF)
299    warning ("junk at end of #pragma weak");
300
301  add_weak (IDENTIFIER_POINTER (name), value ? IDENTIFIER_POINTER (value) : 0);
302}
303#endif
304
305void
306init_pragma ()
307{
308#ifdef HANDLE_PRAGMA_PACK
309  cpp_register_pragma (parse_in, 0, "pack", handle_pragma_pack);
310#endif
311#ifdef HANDLE_PRAGMA_WEAK
312  cpp_register_pragma (parse_in, 0, "weak", handle_pragma_weak);
313#endif
314#ifdef REGISTER_TARGET_PRAGMAS
315  REGISTER_TARGET_PRAGMAS (parse_in);
316#endif
317
318#ifdef HANDLE_PRAGMA_PACK_PUSH_POP
319  ggc_add_root (&alignment_stack, 1, sizeof(alignment_stack),
320		mark_align_stack);
321#endif
322}
323