Add a callback for `__has_include` and use it for dependency scanning.

This adds a preprocessor callback for the `__has_include` and
`__has_include_next` directives.

Successful checking for the presence of a header should add it to the list of
header dependencies so this overrides the callback in the dependency scanner.

Patch by Pete Cooper with some additions by me.

rdar://problem/39545636

Differential Revision: https://reviews.llvm.org/D30882

llvm-svn: 342517

1 files changed, 40 insertions, 0 deletions

diff --git a/clang/test/Frontend/dependency-gen-has-include.c b/clang/test/Frontend/dependency-gen-has-include.c
new file mode 100644
index 00000000000..e8abb2c9c16
--- /dev/null
+++ b/clang/test/Frontend/dependency-gen-has-include.c
@@ -0,0 +1,40 @@
+// REQUIRES: shell
+
+// Basic test
+// RUN: rm -rf %t.dir
+// RUN: mkdir %t.dir
+// RUN: mkdir %t.dir/a
+// RUN: echo "#ifndef HEADER_A" > %t.dir/a/header.h
+// RUN: echo "#define HEADER_A" >> %t.dir/a/header.h
+// RUN: echo "#endif" >> %t.dir/a/header.h
+// RUN: mkdir %t.dir/system
+// RUN: echo "#define SYSTEM_HEADER" > %t.dir/system/system-header.h
+// RUN: mkdir %t.dir/next-a
+// RUN: echo "#if __has_include_next(<next-header.h>)" > %t.dir/next-a/next-header.h
+// RUN: echo "#endif" >> %t.dir/next-a/next-header.h
+// RUN: mkdir %t.dir/next-b
+// RUN: echo "#define NEXT_HEADER" > %t.dir/next-b/next-header.h
+
+// RUN: %clang -MD -MF %t.dir/file.deps %s -fsyntax-only -I %t.dir -isystem %t.dir/system -I %t.dir/next-a -I %t.dir/next-b
+// RUN: FileCheck -input-file=%t.dir/file.deps %s
+// CHECK: dependency-gen-has-include.o
+// CHECK: dependency-gen-has-include.c
+// CHECK: a/header.h
+// CHECK-NOT: missing/file.h
+// CHECK: system/system-header.h
+// CHECK: next-a/next-header.h
+// CHECK: next-b/next-header.h
+
+// Verify that we ignore system headers in user-only headers mode.
+// RUN: %clang -MMD -MF %t.dir/user-headers.deps %s -fsyntax-only -I %t.dir -isystem %t.dir/system -I %t.dir/next-a -I %t.dir/next-b
+// RUN: FileCheck -input-file=%t.dir/user-headers.deps --check-prefix CHECK-USER-HEADER %s
+// CHECK-USER-HEADER-NOT: system/system-header.h
+
+#if __has_include("a/header.h")
+#endif
+#if __has_include("missing/file.h")
+#endif
+#if __has_include(<system-header.h>)
+#endif
+
+#include <next-header.h>