3 files changed, 19 insertions, 0 deletions
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 5fb94e1d440..77e5087b8c7 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -6389,6 +6389,7 @@ CreateAAPCSABIBuiltinVaListDecl(const ASTContext *Context) {
 
   // };
   VaListDecl->completeDefinition();
+  Context->VaListTagDecl = VaListDecl;
 
   // typedef struct __va_list __builtin_va_list;
   QualType T = Context->getRecordType(VaListDecl);
diff --git a/clang/test/PCH/Inputs/__va_list_tag-typedef.h b/clang/test/PCH/Inputs/__va_list_tag-typedef.h
new file mode 100644
index 00000000000..33dc6ad4842
--- /dev/null
+++ b/clang/test/PCH/Inputs/__va_list_tag-typedef.h
@@ -0,0 +1,4 @@
+// Header for PCH test __va_list_tag-typedef.c
+
+#include <stdarg.h>
+typedef va_list va_list_1;
diff --git a/clang/test/PCH/__va_list_tag-typedef.c b/clang/test/PCH/__va_list_tag-typedef.c
new file mode 100644
index 00000000000..c3745ca2cb8
--- /dev/null
+++ b/clang/test/PCH/__va_list_tag-typedef.c
@@ -0,0 +1,14 @@
+// This test checks the patch for the compilation error / crash described in D18557.
+
+// Test as a C source
+// RUN: %clang_cc1 -emit-pch -x c-header -o %t %S/Inputs/__va_list_tag-typedef.h
+// RUN: %clang_cc1 -fsyntax-only -include-pch %t %s
+
+// Test as a C++ source
+// RUN: %clang_cc1 -emit-pch -x c++-header -o %t %S/Inputs/__va_list_tag-typedef.h
+// RUN: %clang_cc1 -x c++ -fsyntax-only -include-pch %t %s
+
+// expected-no-diagnostics
+
+typedef __builtin_va_list va_list_2;
+void test(const char* format, ...) { va_list args; va_start( args, format ); }