[InstallAPI] Add support for aliased exports (#88750)

Apple's ld supports alias_lists, described as
```
     -alias_list filename
             The specified filename contains a list of aliases. The symbol name and its alias are on one
             line, separated by whitespace.  Lines starting with # are ignored.
```
To handle this for installapi-produced TBD files, pass along the same
input and account for it in verification.

clang/include/clang/Basic/DiagnosticInstallAPIKinds.td

@@ -24,6 +24,7 @@ def err_no_matching_target : Error<"no matching target found for target variant
 def err_unsupported_vendor : Error<"vendor '%0' is not supported: '%1'">;
 def err_unsupported_environment : Error<"environment '%0' is not supported: '%1'">;
 def err_unsupported_os : Error<"os '%0' is not supported: '%1'">;
+def err_cannot_read_alias_list : Error<"could not read alias list '%0': %1">;
 } // end of command line category.
 
 let CategoryName = "Verification" in {

clang/include/clang/Driver/Options.td

@@ -1505,6 +1505,7 @@ def end_no_unused_arguments : Flag<["--"], "end-no-unused-arguments">,
 def interface_stub_version_EQ : JoinedOrSeparate<["-"], "interface-stub-version=">,
   Visibility<[ClangOption, CC1Option]>;
 def exported__symbols__list : Separate<["-"], "exported_symbols_list">;
+def alias_list : Separate<["-"], "alias_list">, Flags<[LinkerInput]>;
 def extract_api : Flag<["-"], "extract-api">,
   Visibility<[ClangOption, CC1Option]>, Group<Action_Group>,
   HelpText<"Extract API information">;

clang/include/clang/InstallAPI/DylibVerifier.h

@@ -78,10 +78,12 @@ class DylibVerifier : llvm::MachO::RecordVisitor {
   DylibVerifier() = default;
 
   DylibVerifier(llvm::MachO::Records &&Dylib, ReexportedInterfaces &&Reexports,
-                DiagnosticsEngine *Diag, VerificationMode Mode, bool Zippered,
-                bool Demangle, StringRef DSYMPath)
-      : Dylib(std::move(Dylib)), Reexports(std::move(Reexports)), Mode(Mode),
-        Zippered(Zippered), Demangle(Demangle), DSYMPath(DSYMPath),
+                AliasMap Aliases, DiagnosticsEngine *Diag,
+                VerificationMode Mode, bool Zippered, bool Demangle,
+                StringRef DSYMPath)
+      : Dylib(std::move(Dylib)), Reexports(std::move(Reexports)),
+        Aliases(std::move(Aliases)), Mode(Mode), Zippered(Zippered),
+        Demangle(Demangle), DSYMPath(DSYMPath),
         Exports(std::make_unique<SymbolSet>()), Ctx(VerifierContext{Diag}) {}
 
   Result verify(GlobalRecord *R, const FrontendAttrs *FA);
@@ -104,7 +106,7 @@ class DylibVerifier : llvm::MachO::RecordVisitor {
   void setTarget(const Target &T);
 
   /// Release ownership over exports.
-  std::unique_ptr<SymbolSet> getExports() { return std::move(Exports); }
+  std::unique_ptr<SymbolSet> takeExports();
 
   /// Get result of verification.
   Result getState() const { return Ctx.FrontendState; }
@@ -189,6 +191,9 @@ class DylibVerifier : llvm::MachO::RecordVisitor {
   // Reexported interfaces apart of the library.
   ReexportedInterfaces Reexports;
 
+  // Symbol aliases.
+  AliasMap Aliases;
+
   // Controls what class of violations to report.
   VerificationMode Mode = VerificationMode::Invalid;
 

clang/include/clang/InstallAPI/MachO.h

@@ -23,6 +23,7 @@
 #include "llvm/TextAPI/TextAPIWriter.h"
 #include "llvm/TextAPI/Utils.h"
 
+using AliasMap = llvm::MachO::AliasMap;
 using Architecture = llvm::MachO::Architecture;
 using ArchitectureSet = llvm::MachO::ArchitectureSet;
 using SymbolFlags = llvm::MachO::SymbolFlags;

clang/lib/InstallAPI/DylibVerifier.cpp

@@ -674,6 +674,11 @@ void DylibVerifier::visitSymbolInDylib(const Record &R, SymbolContext &SymCtx) {
     return;
   }
 
+  if (Aliases.count({SymbolName.str(), SymCtx.Kind})) {
+    updateState(Result::Valid);
+    return;
+  }
+
   // All checks at this point classify as some kind of violation.
   // The different verification modes dictate whether they are reported to the
   // user.
@@ -973,5 +978,24 @@ bool DylibVerifier::verifyBinaryAttrs(const ArrayRef<Target> ProvidedTargets,
   return true;
 }
 
+std::unique_ptr<SymbolSet> DylibVerifier::takeExports() {
+  for (const auto &[Alias, Base] : Aliases) {
+    TargetList Targets;
+    SymbolFlags Flags = SymbolFlags::None;
+    if (const Symbol *Sym = Exports->findSymbol(Base.second, Base.first)) {
+      Flags = Sym->getFlags();
+      Targets = {Sym->targets().begin(), Sym->targets().end()};
+    }
+
+    Record R(Alias.first, RecordLinkage::Exported, Flags);
+    SymbolContext SymCtx;
+    SymCtx.SymbolName = Alias.first;
+    SymCtx.Kind = Alias.second;
+    addSymbol(&R, SymCtx, std::move(Targets));
+  }
+
+  return std::move(Exports);
+}
+
 } // namespace installapi
 } // namespace clang