When we attempt to create a built-in that involves a library type we

don't have access to (e.g., fprintf, which needs the library type
FILE), fail with a warning and forget about the builtin
entirely. Previously, we would actually provide an error, which breaks
autoconf's super-lame checks for fprintf, longjmp, etc. Fixes PR8316.

llvm-svn: 122744

2 files changed, 16 insertions, 7 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index abd63198d47..32791f9f983 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -793,13 +793,13 @@ NamedDecl *Sema::LazilyCreateBuiltin(IdentifierInfo *II, unsigned bid,
 
   case ASTContext::GE_Missing_stdio:
     if (ForRedeclaration)
-      Diag(Loc, diag::err_implicit_decl_requires_stdio)
+      Diag(Loc, diag::warn_implicit_decl_requires_stdio)
         << Context.BuiltinInfo.GetName(BID);
     return 0;
 
   case ASTContext::GE_Missing_setjmp:
     if (ForRedeclaration)
-      Diag(Loc, diag::err_implicit_decl_requires_setjmp)
+      Diag(Loc, diag::warn_implicit_decl_requires_setjmp)
         << Context.BuiltinInfo.GetName(BID);
     return 0;
   }
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 6972536e8c2..5ed973b1a80 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -483,12 +483,21 @@ static bool LookupBuiltin(Sema &S, LookupResult &R) {
             S.Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID))
           return false;
         
-        NamedDecl *D = S.LazilyCreateBuiltin((IdentifierInfo *)II, BuiltinID,
-                                             S.TUScope, R.isForRedeclaration(),
-                                             R.getNameLoc());
-        if (D) 
+        if (NamedDecl *D = S.LazilyCreateBuiltin((IdentifierInfo *)II, 
+                                                 BuiltinID, S.TUScope, 
+                                                 R.isForRedeclaration(),
+                                                 R.getNameLoc())) {
           R.addDecl(D);
-        return (D != NULL);
+          return true;
+        }
+
+        if (R.isForRedeclaration()) {
+          // If we're redeclaring this function anyway, forget that
+          // this was a builtin at all.
+          S.Context.BuiltinInfo.ForgetBuiltin(BuiltinID, S.Context.Idents);
+        }
+
+        return false;
       }
     }
   }