1 //===--- Mangle.cpp - Mangle C++ Names --------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Implements generic name mangling support for blocks and Objective-C.
10 //
11 //===----------------------------------------------------------------------===//
12 #include "clang/AST/Attr.h"
13 #include "clang/AST/ASTContext.h"
14 #include "clang/AST/Decl.h"
15 #include "clang/AST/DeclCXX.h"
16 #include "clang/AST/DeclObjC.h"
17 #include "clang/AST/DeclTemplate.h"
18 #include "clang/AST/ExprCXX.h"
19 #include "clang/AST/Mangle.h"
20 #include "clang/AST/VTableBuilder.h"
21 #include "clang/Basic/ABI.h"
22 #include "clang/Basic/SourceManager.h"
23 #include "clang/Basic/TargetInfo.h"
24 #include "llvm/ADT/StringExtras.h"
25 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/Mangler.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/raw_ostream.h"
29 
30 using namespace clang;
31 
32 // FIXME: For blocks we currently mimic GCC's mangling scheme, which leaves
33 // much to be desired. Come up with a better mangling scheme.
34 
35 static void mangleFunctionBlock(MangleContext &Context,
36                                 StringRef Outer,
37                                 const BlockDecl *BD,
38                                 raw_ostream &Out) {
39   unsigned discriminator = Context.getBlockId(BD, true);
40   if (discriminator == 0)
41     Out << "__" << Outer << "_block_invoke";
42   else
43     Out << "__" << Outer << "_block_invoke_" << discriminator+1;
44 }
45 
46 void MangleContext::anchor() { }
47 
48 enum CCMangling {
49   CCM_Other,
50   CCM_Fast,
51   CCM_RegCall,
52   CCM_Vector,
53   CCM_Std,
54   CCM_WasmMainArgcArgv
55 };
56 
57 static bool isExternC(const NamedDecl *ND) {
58   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND))
59     return FD->isExternC();
60   return cast<VarDecl>(ND)->isExternC();
61 }
62 
63 static CCMangling getCallingConvMangling(const ASTContext &Context,
64                                          const NamedDecl *ND) {
65   const TargetInfo &TI = Context.getTargetInfo();
66   const llvm::Triple &Triple = TI.getTriple();
67 
68   // On wasm, the argc/argv form of "main" is renamed so that the startup code
69   // can call it with the correct function signature.
70   // On Emscripten, users may be exporting "main" and expecting to call it
71   // themselves, so we can't mangle it.
72   if (Triple.isWasm() && !Triple.isOSEmscripten())
73     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND))
74       if (FD->isMain() && FD->hasPrototype() && FD->param_size() == 2)
75         return CCM_WasmMainArgcArgv;
76 
77   if (!Triple.isOSWindows() || !Triple.isX86())
78     return CCM_Other;
79 
80   if (Context.getLangOpts().CPlusPlus && !isExternC(ND) &&
81       TI.getCXXABI() == TargetCXXABI::Microsoft)
82     return CCM_Other;
83 
84   const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND);
85   if (!FD)
86     return CCM_Other;
87   QualType T = FD->getType();
88 
89   const FunctionType *FT = T->castAs<FunctionType>();
90 
91   CallingConv CC = FT->getCallConv();
92   switch (CC) {
93   default:
94     return CCM_Other;
95   case CC_X86FastCall:
96     return CCM_Fast;
97   case CC_X86StdCall:
98     return CCM_Std;
99   case CC_X86VectorCall:
100     return CCM_Vector;
101   }
102 }
103 
104 bool MangleContext::shouldMangleDeclName(const NamedDecl *D) {
105   const ASTContext &ASTContext = getASTContext();
106 
107   CCMangling CC = getCallingConvMangling(ASTContext, D);
108   if (CC != CCM_Other)
109     return true;
110 
111   // If the declaration has an owning module for linkage purposes that needs to
112   // be mangled, we must mangle its name.
113   if (!D->hasExternalFormalLinkage() && D->getOwningModuleForLinkage())
114     return true;
115 
116   // In C, functions with no attributes never need to be mangled. Fastpath them.
117   if (!getASTContext().getLangOpts().CPlusPlus && !D->hasAttrs())
118     return false;
119 
120   // Any decl can be declared with __asm("foo") on it, and this takes precedence
121   // over all other naming in the .o file.
122   if (D->hasAttr<AsmLabelAttr>())
123     return true;
124 
125   return shouldMangleCXXName(D);
126 }
127 
128 void MangleContext::mangleName(GlobalDecl GD, raw_ostream &Out) {
129   const NamedDecl *D = cast<NamedDecl>(GD.getDecl());
130   // Any decl can be declared with __asm("foo") on it, and this takes precedence
131   // over all other naming in the .o file.
132   if (const AsmLabelAttr *ALA = D->getAttr<AsmLabelAttr>()) {
133     // If we have an asm name, then we use it as the mangling.
134 
135     // If the label isn't literal, or if this is an alias for an LLVM intrinsic,
136     // do not add a "\01" prefix.
137     if (!ALA->getIsLiteralLabel() || ALA->getLabel().startswith("llvm.")) {
138       Out << ALA->getLabel();
139       return;
140     }
141 
142     // Adding the prefix can cause problems when one file has a "foo" and
143     // another has a "\01foo". That is known to happen on ELF with the
144     // tricks normally used for producing aliases (PR9177). Fortunately the
145     // llvm mangler on ELF is a nop, so we can just avoid adding the \01
146     // marker.
147     char GlobalPrefix =
148         getASTContext().getTargetInfo().getDataLayout().getGlobalPrefix();
149     if (GlobalPrefix)
150       Out << '\01'; // LLVM IR Marker for __asm("foo")
151 
152     Out << ALA->getLabel();
153     return;
154   }
155 
156   const ASTContext &ASTContext = getASTContext();
157   CCMangling CC = getCallingConvMangling(ASTContext, D);
158 
159   if (CC == CCM_WasmMainArgcArgv) {
160     Out << "__main_argc_argv";
161     return;
162   }
163 
164   bool MCXX = shouldMangleCXXName(D);
165   const TargetInfo &TI = Context.getTargetInfo();
166   if (CC == CCM_Other || (MCXX && TI.getCXXABI() == TargetCXXABI::Microsoft)) {
167     if (const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(D))
168       mangleObjCMethodName(OMD, Out);
169     else
170       mangleCXXName(GD, Out);
171     return;
172   }
173 
174   Out << '\01';
175   if (CC == CCM_Std)
176     Out << '_';
177   else if (CC == CCM_Fast)
178     Out << '@';
179   else if (CC == CCM_RegCall)
180     Out << "__regcall3__";
181 
182   if (!MCXX)
183     Out << D->getIdentifier()->getName();
184   else if (const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(D))
185     mangleObjCMethodName(OMD, Out);
186   else
187     mangleCXXName(GD, Out);
188 
189   const FunctionDecl *FD = cast<FunctionDecl>(D);
190   const FunctionType *FT = FD->getType()->castAs<FunctionType>();
191   const FunctionProtoType *Proto = dyn_cast<FunctionProtoType>(FT);
192   if (CC == CCM_Vector)
193     Out << '@';
194   Out << '@';
195   if (!Proto) {
196     Out << '0';
197     return;
198   }
199   assert(!Proto->isVariadic());
200   unsigned ArgWords = 0;
201   if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD))
202     if (!MD->isStatic())
203       ++ArgWords;
204   for (const auto &AT : Proto->param_types())
205     // Size should be aligned to pointer size.
206     ArgWords +=
207         llvm::alignTo(ASTContext.getTypeSize(AT), TI.getPointerWidth(0)) /
208         TI.getPointerWidth(0);
209   Out << ((TI.getPointerWidth(0) / 8) * ArgWords);
210 }
211 
212 void MangleContext::mangleGlobalBlock(const BlockDecl *BD,
213                                       const NamedDecl *ID,
214                                       raw_ostream &Out) {
215   unsigned discriminator = getBlockId(BD, false);
216   if (ID) {
217     if (shouldMangleDeclName(ID))
218       mangleName(ID, Out);
219     else {
220       Out << ID->getIdentifier()->getName();
221     }
222   }
223   if (discriminator == 0)
224     Out << "_block_invoke";
225   else
226     Out << "_block_invoke_" << discriminator+1;
227 }
228 
229 void MangleContext::mangleCtorBlock(const CXXConstructorDecl *CD,
230                                     CXXCtorType CT, const BlockDecl *BD,
231                                     raw_ostream &ResStream) {
232   SmallString<64> Buffer;
233   llvm::raw_svector_ostream Out(Buffer);
234   mangleName(GlobalDecl(CD, CT), Out);
235   mangleFunctionBlock(*this, Buffer, BD, ResStream);
236 }
237 
238 void MangleContext::mangleDtorBlock(const CXXDestructorDecl *DD,
239                                     CXXDtorType DT, const BlockDecl *BD,
240                                     raw_ostream &ResStream) {
241   SmallString<64> Buffer;
242   llvm::raw_svector_ostream Out(Buffer);
243   mangleName(GlobalDecl(DD, DT), Out);
244   mangleFunctionBlock(*this, Buffer, BD, ResStream);
245 }
246 
247 void MangleContext::mangleBlock(const DeclContext *DC, const BlockDecl *BD,
248                                 raw_ostream &Out) {
249   assert(!isa<CXXConstructorDecl>(DC) && !isa<CXXDestructorDecl>(DC));
250 
251   SmallString<64> Buffer;
252   llvm::raw_svector_ostream Stream(Buffer);
253   if (const ObjCMethodDecl *Method = dyn_cast<ObjCMethodDecl>(DC)) {
254     mangleObjCMethodName(Method, Stream);
255   } else {
256     assert((isa<NamedDecl>(DC) || isa<BlockDecl>(DC)) &&
257            "expected a NamedDecl or BlockDecl");
258     if (isa<BlockDecl>(DC))
259       for (; DC && isa<BlockDecl>(DC); DC = DC->getParent())
260         (void) getBlockId(cast<BlockDecl>(DC), true);
261     assert((isa<TranslationUnitDecl>(DC) || isa<NamedDecl>(DC)) &&
262            "expected a TranslationUnitDecl or a NamedDecl");
263     if (const auto *CD = dyn_cast<CXXConstructorDecl>(DC))
264       mangleCtorBlock(CD, /*CT*/ Ctor_Complete, BD, Out);
265     else if (const auto *DD = dyn_cast<CXXDestructorDecl>(DC))
266       mangleDtorBlock(DD, /*DT*/ Dtor_Complete, BD, Out);
267     else if (auto ND = dyn_cast<NamedDecl>(DC)) {
268       if (!shouldMangleDeclName(ND) && ND->getIdentifier())
269         Stream << ND->getIdentifier()->getName();
270       else {
271         // FIXME: We were doing a mangleUnqualifiedName() before, but that's
272         // a private member of a class that will soon itself be private to the
273         // Itanium C++ ABI object. What should we do now? Right now, I'm just
274         // calling the mangleName() method on the MangleContext; is there a
275         // better way?
276         mangleName(ND, Stream);
277       }
278     }
279   }
280   mangleFunctionBlock(*this, Buffer, BD, Out);
281 }
282 
283 void MangleContext::mangleObjCMethodNameWithoutSize(const ObjCMethodDecl *MD,
284                                                     raw_ostream &OS) {
285   const ObjCContainerDecl *CD =
286   dyn_cast<ObjCContainerDecl>(MD->getDeclContext());
287   assert (CD && "Missing container decl in GetNameForMethod");
288   OS << (MD->isInstanceMethod() ? '-' : '+') << '[';
289   if (const ObjCCategoryImplDecl *CID = dyn_cast<ObjCCategoryImplDecl>(CD)) {
290     OS << CID->getClassInterface()->getName();
291     OS << '(' << *CID << ')';
292   } else {
293     OS << CD->getName();
294   }
295   OS << ' ';
296   MD->getSelector().print(OS);
297   OS << ']';
298 }
299 
300 void MangleContext::mangleObjCMethodName(const ObjCMethodDecl *MD,
301                                          raw_ostream &Out) {
302   SmallString<64> Name;
303   llvm::raw_svector_ostream OS(Name);
304 
305   mangleObjCMethodNameWithoutSize(MD, OS);
306   Out << OS.str().size() << OS.str();
307 }
308 
309 class ASTNameGenerator::Implementation {
310   std::unique_ptr<MangleContext> MC;
311   llvm::DataLayout DL;
312 
313 public:
314   explicit Implementation(ASTContext &Ctx)
315       : MC(Ctx.createMangleContext()), DL(Ctx.getTargetInfo().getDataLayout()) {
316   }
317 
318   bool writeName(const Decl *D, raw_ostream &OS) {
319     // First apply frontend mangling.
320     SmallString<128> FrontendBuf;
321     llvm::raw_svector_ostream FrontendBufOS(FrontendBuf);
322     if (auto *FD = dyn_cast<FunctionDecl>(D)) {
323       if (FD->isDependentContext())
324         return true;
325       if (writeFuncOrVarName(FD, FrontendBufOS))
326         return true;
327     } else if (auto *VD = dyn_cast<VarDecl>(D)) {
328       if (writeFuncOrVarName(VD, FrontendBufOS))
329         return true;
330     } else if (auto *MD = dyn_cast<ObjCMethodDecl>(D)) {
331       MC->mangleObjCMethodNameWithoutSize(MD, OS);
332       return false;
333     } else if (auto *ID = dyn_cast<ObjCInterfaceDecl>(D)) {
334       writeObjCClassName(ID, FrontendBufOS);
335     } else {
336       return true;
337     }
338 
339     // Now apply backend mangling.
340     llvm::Mangler::getNameWithPrefix(OS, FrontendBufOS.str(), DL);
341     return false;
342   }
343 
344   std::string getName(const Decl *D) {
345     std::string Name;
346     {
347       llvm::raw_string_ostream OS(Name);
348       writeName(D, OS);
349     }
350     return Name;
351   }
352 
353   enum ObjCKind {
354     ObjCClass,
355     ObjCMetaclass,
356   };
357 
358   static StringRef getClassSymbolPrefix(ObjCKind Kind,
359                                         const ASTContext &Context) {
360     if (Context.getLangOpts().ObjCRuntime.isGNUFamily())
361       return Kind == ObjCMetaclass ? "_OBJC_METACLASS_" : "_OBJC_CLASS_";
362     return Kind == ObjCMetaclass ? "OBJC_METACLASS_$_" : "OBJC_CLASS_$_";
363   }
364 
365   std::vector<std::string> getAllManglings(const ObjCContainerDecl *OCD) {
366     StringRef ClassName;
367     if (const auto *OID = dyn_cast<ObjCInterfaceDecl>(OCD))
368       ClassName = OID->getObjCRuntimeNameAsString();
369     else if (const auto *OID = dyn_cast<ObjCImplementationDecl>(OCD))
370       ClassName = OID->getObjCRuntimeNameAsString();
371 
372     if (ClassName.empty())
373       return {};
374 
375     auto Mangle = [&](ObjCKind Kind, StringRef ClassName) -> std::string {
376       SmallString<40> Mangled;
377       auto Prefix = getClassSymbolPrefix(Kind, OCD->getASTContext());
378       llvm::Mangler::getNameWithPrefix(Mangled, Prefix + ClassName, DL);
379       return std::string(Mangled.str());
380     };
381 
382     return {
383         Mangle(ObjCClass, ClassName),
384         Mangle(ObjCMetaclass, ClassName),
385     };
386   }
387 
388   std::vector<std::string> getAllManglings(const Decl *D) {
389     if (const auto *OCD = dyn_cast<ObjCContainerDecl>(D))
390       return getAllManglings(OCD);
391 
392     if (!(isa<CXXRecordDecl>(D) || isa<CXXMethodDecl>(D)))
393       return {};
394 
395     const NamedDecl *ND = cast<NamedDecl>(D);
396 
397     ASTContext &Ctx = ND->getASTContext();
398     std::unique_ptr<MangleContext> M(Ctx.createMangleContext());
399 
400     std::vector<std::string> Manglings;
401 
402     auto hasDefaultCXXMethodCC = [](ASTContext &C, const CXXMethodDecl *MD) {
403       auto DefaultCC = C.getDefaultCallingConvention(/*IsVariadic=*/false,
404                                                      /*IsCXXMethod=*/true);
405       auto CC = MD->getType()->castAs<FunctionProtoType>()->getCallConv();
406       return CC == DefaultCC;
407     };
408 
409     if (const auto *CD = dyn_cast_or_null<CXXConstructorDecl>(ND)) {
410       Manglings.emplace_back(getMangledStructor(CD, Ctor_Base));
411 
412       if (Ctx.getTargetInfo().getCXXABI().isItaniumFamily())
413         if (!CD->getParent()->isAbstract())
414           Manglings.emplace_back(getMangledStructor(CD, Ctor_Complete));
415 
416       if (Ctx.getTargetInfo().getCXXABI().isMicrosoft())
417         if (CD->hasAttr<DLLExportAttr>() && CD->isDefaultConstructor())
418           if (!(hasDefaultCXXMethodCC(Ctx, CD) && CD->getNumParams() == 0))
419             Manglings.emplace_back(getMangledStructor(CD, Ctor_DefaultClosure));
420     } else if (const auto *DD = dyn_cast_or_null<CXXDestructorDecl>(ND)) {
421       Manglings.emplace_back(getMangledStructor(DD, Dtor_Base));
422       if (Ctx.getTargetInfo().getCXXABI().isItaniumFamily()) {
423         Manglings.emplace_back(getMangledStructor(DD, Dtor_Complete));
424         if (DD->isVirtual())
425           Manglings.emplace_back(getMangledStructor(DD, Dtor_Deleting));
426       }
427     } else if (const auto *MD = dyn_cast_or_null<CXXMethodDecl>(ND)) {
428       Manglings.emplace_back(getName(ND));
429       if (MD->isVirtual())
430         if (const auto *TIV = Ctx.getVTableContext()->getThunkInfo(MD))
431           for (const auto &T : *TIV)
432             Manglings.emplace_back(getMangledThunk(MD, T));
433     }
434 
435     return Manglings;
436   }
437 
438 private:
439   bool writeFuncOrVarName(const NamedDecl *D, raw_ostream &OS) {
440     if (MC->shouldMangleDeclName(D)) {
441       GlobalDecl GD;
442       if (const auto *CtorD = dyn_cast<CXXConstructorDecl>(D))
443         GD = GlobalDecl(CtorD, Ctor_Complete);
444       else if (const auto *DtorD = dyn_cast<CXXDestructorDecl>(D))
445         GD = GlobalDecl(DtorD, Dtor_Complete);
446       else if (D->hasAttr<CUDAGlobalAttr>())
447         GD = GlobalDecl::getDefaultKernelReference(cast<FunctionDecl>(D));
448       else
449         GD = GlobalDecl(D);
450       MC->mangleName(GD, OS);
451       return false;
452     } else {
453       IdentifierInfo *II = D->getIdentifier();
454       if (!II)
455         return true;
456       OS << II->getName();
457       return false;
458     }
459   }
460 
461   void writeObjCClassName(const ObjCInterfaceDecl *D, raw_ostream &OS) {
462     OS << getClassSymbolPrefix(ObjCClass, D->getASTContext());
463     OS << D->getObjCRuntimeNameAsString();
464   }
465 
466   std::string getMangledStructor(const NamedDecl *ND, unsigned StructorType) {
467     std::string FrontendBuf;
468     llvm::raw_string_ostream FOS(FrontendBuf);
469 
470     GlobalDecl GD;
471     if (const auto *CD = dyn_cast_or_null<CXXConstructorDecl>(ND))
472       GD = GlobalDecl(CD, static_cast<CXXCtorType>(StructorType));
473     else if (const auto *DD = dyn_cast_or_null<CXXDestructorDecl>(ND))
474       GD = GlobalDecl(DD, static_cast<CXXDtorType>(StructorType));
475     MC->mangleName(GD, FOS);
476 
477     std::string BackendBuf;
478     llvm::raw_string_ostream BOS(BackendBuf);
479 
480     llvm::Mangler::getNameWithPrefix(BOS, FOS.str(), DL);
481 
482     return BOS.str();
483   }
484 
485   std::string getMangledThunk(const CXXMethodDecl *MD, const ThunkInfo &T) {
486     std::string FrontendBuf;
487     llvm::raw_string_ostream FOS(FrontendBuf);
488 
489     MC->mangleThunk(MD, T, FOS);
490 
491     std::string BackendBuf;
492     llvm::raw_string_ostream BOS(BackendBuf);
493 
494     llvm::Mangler::getNameWithPrefix(BOS, FOS.str(), DL);
495 
496     return BOS.str();
497   }
498 };
499 
500 ASTNameGenerator::ASTNameGenerator(ASTContext &Ctx)
501     : Impl(std::make_unique<Implementation>(Ctx)) {}
502 
503 ASTNameGenerator::~ASTNameGenerator() {}
504 
505 bool ASTNameGenerator::writeName(const Decl *D, raw_ostream &OS) {
506   return Impl->writeName(D, OS);
507 }
508 
509 std::string ASTNameGenerator::getName(const Decl *D) {
510   return Impl->getName(D);
511 }
512 
513 std::vector<std::string> ASTNameGenerator::getAllManglings(const Decl *D) {
514   return Impl->getAllManglings(D);
515 }
516