Process attributes 'ifunc' and 'alias' when checking for redefinition

These attributes effectively turn a non-defining declaration into a
definition, so the case when the declaration already has a body must
be diagnosed properly.

Differential Revision: https://reviews.llvm.org/D30032

llvm-svn: 295541

clang/lib/Sema/SemaDecl.cpp

@@ -11786,6 +11786,18 @@ Decl *Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Decl *D,
   else
     FD = cast<FunctionDecl>(D);
 
+  // Check for defining attributes before the check for redefinition.
+  if (const auto *Attr = FD->getAttr<AliasAttr>()) {
+    Diag(Attr->getLocation(), diag::err_alias_is_definition) << FD << 0;
+    FD->dropAttr<AliasAttr>();
+    FD->setInvalidDecl();
+  }
+  if (const auto *Attr = FD->getAttr<IFuncAttr>()) {
+    Diag(Attr->getLocation(), diag::err_alias_is_definition) << FD << 1;
+    FD->dropAttr<IFuncAttr>();
+    FD->setInvalidDecl();
+  }
+
   // See if this is a redefinition.
   if (!FD->isLateTemplateParsed()) {
     CheckForFunctionRedefinition(FD, nullptr, SkipBody);

clang/test/Sema/alias-redefinition.c

@@ -19,9 +19,8 @@ void f4() {}
 void fun4(void) __attribute((alias("f4")));
 void fun4(void);
 
-// FIXME: We should produce a special case error for this.
 void f5() {}
-void __attribute((alias("f5"))) fun5(void) {} // expected-error {{redefinition of 'fun5'}} // expected-note {{previous definition}}
+void __attribute((alias("f5"))) fun5(void) {} // expected-error {{definition 'fun5' cannot also be an alias}}
 
 int var1 __attribute((alias("v1"))); // expected-error {{definition 'var1' cannot also be an alias}}
 static int var2 __attribute((alias("v2"))) = 2; // expected-error {{definition 'var2' cannot also be an alias}}

clang/test/Sema/attr-ifunc.c

@@ -39,5 +39,9 @@ void f1() __attribute__((ifunc("f1_ifunc")));
 //expected-error@-1 {{definition with same mangled name as another definition}}
 void* f1_ifunc() { return 0; }
 
+void* f6_ifunc(int i);
+void __attribute__((ifunc("f6_ifunc"))) f6() {}
+//expected-error@-1 {{definition 'f6' cannot also be an ifunc}}
+
 #endif
 #endif