Give files from #line the characteristics of the current file
This allows #line directives to appear in system headers that have code
that clang would normally warn on. This is compatible with GCC, which is
easy to test by running `gcc -E`.
Fixes PR30752
llvm-svn: 303582
diff --git a/clang/test/Frontend/system-header-line-directive.c b/clang/test/Frontend/system-header-line-directive.c
new file mode 100644
index 0000000..16dde643
--- /dev/null
+++ b/clang/test/Frontend/system-header-line-directive.c
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -Wall %s -isystem %S/Inputs/SystemHeaderPrefix -verify
+// RUN: %clang_cc1 %s -E -o - -isystem %S/Inputs/SystemHeaderPrefix | FileCheck %s
+#include <noline.h>
+#include <line.h>
+
+// This tests that "#line" directives in system headers preserve system
+// header-ness just like GNU line markers that don't have filenames. This was
+// PR30752.
+
+// expected-no-diagnostics
+
+// CHECK: # {{[0-9]+}} "{{.*}}system-header-line-directive.c" 2
+// CHECK: # 1 "{{.*}}noline.h" 1 3
+// CHECK: foo();
+// CHECK: # 4 "{{.*}}system-header-line-directive.c" 2
+// CHECK: # 1 "{{.*}}line.h" 1 3
+// The "3" below indicates that "foo.h" is considered a system header.
+// CHECK: # 1 "foo.h" 3
+// CHECK: foo();
+// CHECK: # {{[0-9]+}} "{{.*}}system-header-line-directive.c" 2