SemaAttr.cpp revision 210299 
1//===--- SemaAttr.cpp - Semantic Analysis for Attributes ------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements semantic analysis for non-trivial attributes and
11// pragmas.
12//
13//===----------------------------------------------------------------------===//
14
15#include "Sema.h"
16#include "Lookup.h"
17#include "clang/AST/Expr.h"
18#include "clang/Basic/TargetInfo.h"
19#include "clang/Lex/Preprocessor.h"
20using namespace clang;
21
22//===----------------------------------------------------------------------===//
23// Pragma 'pack' and 'options align'
24//===----------------------------------------------------------------------===//
25
26namespace {
27  struct PackStackEntry {
28    // We just use a sentinel to represent when the stack is set to mac68k
29    // alignment.
30    static const unsigned kMac68kAlignmentSentinel = ~0U;
31
32    unsigned Alignment;
33    IdentifierInfo *Name;
34  };
35
36  /// PragmaPackStack - Simple class to wrap the stack used by #pragma
37  /// pack.
38  class PragmaPackStack {
39    typedef std::vector<PackStackEntry> stack_ty;
40
41    /// Alignment - The current user specified alignment.
42    unsigned Alignment;
43
44    /// Stack - Entries in the #pragma pack stack, consisting of saved
45    /// alignments and optional names.
46    stack_ty Stack;
47
48  public:
49    PragmaPackStack() : Alignment(0) {}
50
51    void setAlignment(unsigned A) { Alignment = A; }
52    unsigned getAlignment() { return Alignment; }
53
54    /// push - Push the current alignment onto the stack, optionally
55    /// using the given \arg Name for the record, if non-zero.
56    void push(IdentifierInfo *Name) {
57      PackStackEntry PSE = { Alignment, Name };
58      Stack.push_back(PSE);
59    }
60
61    /// pop - Pop a record from the stack and restore the current
62    /// alignment to the previous value. If \arg Name is non-zero then
63    /// the first such named record is popped, otherwise the top record
64    /// is popped. Returns true if the pop succeeded.
65    bool pop(IdentifierInfo *Name);
66  };
67}  // end anonymous namespace.
68
69bool PragmaPackStack::pop(IdentifierInfo *Name) {
70  if (Stack.empty())
71    return false;
72
73  // If name is empty just pop top.
74  if (!Name) {
75    Alignment = Stack.back().Alignment;
76    Stack.pop_back();
77    return true;
78  }
79
80  // Otherwise, find the named record.
81  for (unsigned i = Stack.size(); i != 0; ) {
82    --i;
83    if (Stack[i].Name == Name) {
84      // Found it, pop up to and including this record.
85      Alignment = Stack[i].Alignment;
86      Stack.erase(Stack.begin() + i, Stack.end());
87      return true;
88    }
89  }
90
91  return false;
92}
93
94
95/// FreePackedContext - Deallocate and null out PackContext.
96void Sema::FreePackedContext() {
97  delete static_cast<PragmaPackStack*>(PackContext);
98  PackContext = 0;
99}
100
101void Sema::AddAlignmentAttributesForRecord(RecordDecl *RD) {
102  // If there is no pack context, we don't need any attributes.
103  if (!PackContext)
104    return;
105
106  PragmaPackStack *Stack = static_cast<PragmaPackStack*>(PackContext);
107
108  // Otherwise, check to see if we need a max field alignment attribute.
109  if (unsigned Alignment = Stack->getAlignment()) {
110    if (Alignment == PackStackEntry::kMac68kAlignmentSentinel)
111      RD->addAttr(::new (Context) AlignMac68kAttr());
112    else
113      RD->addAttr(::new (Context) MaxFieldAlignmentAttr(Alignment * 8));
114  }
115}
116
117void Sema::ActOnPragmaOptionsAlign(PragmaOptionsAlignKind Kind,
118                                   SourceLocation PragmaLoc,
119                                   SourceLocation KindLoc) {
120  if (PackContext == 0)
121    PackContext = new PragmaPackStack();
122
123  PragmaPackStack *Context = static_cast<PragmaPackStack*>(PackContext);
124
125  // Reset just pops the top of the stack.
126  if (Kind == Action::POAK_Reset) {
127    // Do the pop.
128    if (!Context->pop(0)) {
129      // If a name was specified then failure indicates the name
130      // wasn't found. Otherwise failure indicates the stack was
131      // empty.
132      Diag(PragmaLoc, diag::warn_pragma_options_align_reset_failed)
133        << "stack empty";
134    }
135    return;
136  }
137
138  switch (Kind) {
139    // For all targets we support native and natural are the same.
140    //
141    // FIXME: This is not true on Darwin/PPC.
142  case POAK_Native:
143  case POAK_Power:
144  case POAK_Natural:
145    Context->push(0);
146    Context->setAlignment(0);
147    break;
148
149    // Note that '#pragma options align=packed' is not equivalent to attribute
150    // packed, it has a different precedence relative to attribute aligned.
151  case POAK_Packed:
152    Context->push(0);
153    Context->setAlignment(1);
154    break;
155
156  case POAK_Mac68k:
157    // Check if the target supports this.
158    if (!PP.getTargetInfo().hasAlignMac68kSupport()) {
159      Diag(PragmaLoc, diag::err_pragma_options_align_mac68k_target_unsupported);
160      return;
161    }
162    Context->push(0);
163    Context->setAlignment(PackStackEntry::kMac68kAlignmentSentinel);
164    break;
165
166  default:
167    Diag(PragmaLoc, diag::warn_pragma_options_align_unsupported_option)
168      << KindLoc;
169    break;
170  }
171}
172
173void Sema::ActOnPragmaPack(PragmaPackKind Kind, IdentifierInfo *Name,
174                           ExprTy *alignment, SourceLocation PragmaLoc,
175                           SourceLocation LParenLoc, SourceLocation RParenLoc) {
176  Expr *Alignment = static_cast<Expr *>(alignment);
177
178  // If specified then alignment must be a "small" power of two.
179  unsigned AlignmentVal = 0;
180  if (Alignment) {
181    llvm::APSInt Val;
182
183    // pack(0) is like pack(), which just works out since that is what
184    // we use 0 for in PackAttr.
185    if (Alignment->isTypeDependent() ||
186        Alignment->isValueDependent() ||
187        !Alignment->isIntegerConstantExpr(Val, Context) ||
188        !(Val == 0 || Val.isPowerOf2()) ||
189        Val.getZExtValue() > 16) {
190      Diag(PragmaLoc, diag::warn_pragma_pack_invalid_alignment);
191      Alignment->Destroy(Context);
192      return; // Ignore
193    }
194
195    AlignmentVal = (unsigned) Val.getZExtValue();
196  }
197
198  if (PackContext == 0)
199    PackContext = new PragmaPackStack();
200
201  PragmaPackStack *Context = static_cast<PragmaPackStack*>(PackContext);
202
203  switch (Kind) {
204  case Action::PPK_Default: // pack([n])
205    Context->setAlignment(AlignmentVal);
206    break;
207
208  case Action::PPK_Show: // pack(show)
209    // Show the current alignment, making sure to show the right value
210    // for the default.
211    AlignmentVal = Context->getAlignment();
212    // FIXME: This should come from the target.
213    if (AlignmentVal == 0)
214      AlignmentVal = 8;
215    if (AlignmentVal == PackStackEntry::kMac68kAlignmentSentinel)
216      Diag(PragmaLoc, diag::warn_pragma_pack_show) << "mac68k";
217    else
218      Diag(PragmaLoc, diag::warn_pragma_pack_show) << AlignmentVal;
219    break;
220
221  case Action::PPK_Push: // pack(push [, id] [, [n])
222    Context->push(Name);
223    // Set the new alignment if specified.
224    if (Alignment)
225      Context->setAlignment(AlignmentVal);
226    break;
227
228  case Action::PPK_Pop: // pack(pop [, id] [,  n])
229    // MSDN, C/C++ Preprocessor Reference > Pragma Directives > pack:
230    // "#pragma pack(pop, identifier, n) is undefined"
231    if (Alignment && Name)
232      Diag(PragmaLoc, diag::warn_pragma_pack_pop_identifer_and_alignment);
233
234    // Do the pop.
235    if (!Context->pop(Name)) {
236      // If a name was specified then failure indicates the name
237      // wasn't found. Otherwise failure indicates the stack was
238      // empty.
239      Diag(PragmaLoc, diag::warn_pragma_pack_pop_failed)
240        << (Name ? "no record matching name" : "stack empty");
241
242      // FIXME: Warn about popping named records as MSVC does.
243    } else {
244      // Pop succeeded, set the new alignment if specified.
245      if (Alignment)
246        Context->setAlignment(AlignmentVal);
247    }
248    break;
249
250  default:
251    assert(0 && "Invalid #pragma pack kind.");
252  }
253}
254
255void Sema::ActOnPragmaUnused(const Token *Identifiers, unsigned NumIdentifiers,
256                             Scope *curScope,
257                             SourceLocation PragmaLoc,
258                             SourceLocation LParenLoc,
259                             SourceLocation RParenLoc) {
260
261  for (unsigned i = 0; i < NumIdentifiers; ++i) {
262    const Token &Tok = Identifiers[i];
263    IdentifierInfo *Name = Tok.getIdentifierInfo();
264    LookupResult Lookup(*this, Name, Tok.getLocation(), LookupOrdinaryName);
265    LookupParsedName(Lookup, curScope, NULL, true);
266
267    if (Lookup.empty()) {
268      Diag(PragmaLoc, diag::warn_pragma_unused_undeclared_var)
269        << Name << SourceRange(Tok.getLocation());
270      continue;
271    }
272
273    VarDecl *VD = Lookup.getAsSingle<VarDecl>();
274    if (!VD || !VD->hasLocalStorage()) {
275      Diag(PragmaLoc, diag::warn_pragma_unused_expected_localvar)
276        << Name << SourceRange(Tok.getLocation());
277      continue;
278    }
279
280    VD->addAttr(::new (Context) UnusedAttr());
281  }
282}
283