Don't forget about a builtin if we're about to redeclare it and we couldn't

create an implicit declaration of it (because some type it depends on is
unavailable). This had the effect of causing us to not implicitly give it the
right attributes. It turns out that glibc's __sigsetjmp is declared before
sigjmp_buf is declared, and this resulted in us not implicitly giving it
__attribute__((returns_twice)), which in turn resulted in miscompiles in any C
code calling glibc's sigsetjmp.

(See also the vaguely-related sourceware.org/PR4662.)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199850 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index 0f5a78b10a1a21433029f632ee647baa8d0fe1ed..01220769e329506d3a8589e6396c6d6e46f0eb81 100644 (file)
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -545,14 +545,6 @@ static bool LookupBuiltin(Sema &S, LookupResult &R) {
           R.addDecl(D);
           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;
       }
     }
   }

diff --git a/test/Sema/implicit-builtin-decl.c b/test/Sema/implicit-builtin-decl.c
index d7ec16953a09c470ee3b99e3cf24ee139ffb61ba..2a7a7ca27b62c14a578d4e23f29a72c0caa0fa63 100644 (file)
--- a/test/Sema/implicit-builtin-decl.c
+++ b/test/Sema/implicit-builtin-decl.c
@@ -1,4 +1,6 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: not %clang_cc1 -fsyntax-only -ast-dump %s | FileCheck %s
+
 void f() {
   int *ptr = malloc(sizeof(int) * 10); // expected-warning{{implicitly declaring library function 'malloc' with type}} \
   // expected-note{{please include the header <stdlib.h> or explicitly provide a declaration for 'malloc'}} \
@@ -57,3 +59,10 @@ void snprintf() { }
 void longjmp(); // expected-warning{{declaration of built-in function 'longjmp' requires inclusion of the header <setjmp.h>}}
 
 extern float fmaxf(float, float);
+
+struct __jmp_buf_tag {};
+void sigsetjmp(struct __jmp_buf_tag[1], int); // expected-warning{{declaration of built-in function 'sigsetjmp' requires inclusion of the header <setjmp.h>}}
+
+// CHECK:     FunctionDecl {{.*}} <line:[[@LINE-2]]:1, col:44> sigsetjmp '
+// CHECK-NOT: FunctionDecl
+// CHECK:     ReturnsTwiceAttr {{.*}} <{{.*}}> Implicit