[Modules] Turn on system header validation for implicit modules

After r300027 implicit builds might fail when updating the SDK on
darwin. Make validation of system headers default when implicit modules
is on and allow modules to be rebuild when system headers change.

rdar://problem/19767523

llvm-svn: 330240

3 files changed, 15 insertions, 1 deletions

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 55e87287585..d8e784a8abb 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1217,6 +1217,8 @@ def fmodules_disable_diagnostic_validation : Flag<["-"], "fmodules-disable-diagn
 def fmodules_validate_system_headers : Flag<["-"], "fmodules-validate-system-headers">,
   Group<i_Group>, Flags<[CC1Option]>,
   HelpText<"Validate the system headers that a module depends on when loading the module">;
+def fno_modules_validate_system_headers : Flag<["-"], "fno-modules-validate-system-headers">,
+  Group<i_Group>, Flags<[DriverOption]>;
 def fmodules : Flag <["-"], "fmodules">, Group<f_Group>,
   Flags<[DriverOption, CC1Option]>,
   HelpText<"Enable the 'modules' language feature">;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 6de4f6ea620..15e7cf2847c 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -2546,11 +2546,13 @@ static void RenderModulesOptions(Compilation &C, const Driver &D,
     CmdArgs.push_back("-fmodules-strict-decluse");
 
   // -fno-implicit-modules turns off implicitly compiling modules on demand.
+  bool ImplicitModules = false;
   if (!Args.hasFlag(options::OPT_fimplicit_modules,
                     options::OPT_fno_implicit_modules, HaveClangModules)) {
     if (HaveModules)
       CmdArgs.push_back("-fno-implicit-modules");
   } else if (HaveModules) {
+    ImplicitModules = true;
     // -fmodule-cache-path specifies where our implicitly-built module files
     // should be written.
     SmallString<128> Path;
@@ -2657,7 +2659,11 @@ static void RenderModulesOptions(Compilation &C, const Driver &D,
                     options::OPT_fmodules_validate_once_per_build_session);
   }
 
-  Args.AddLastArg(CmdArgs, options::OPT_fmodules_validate_system_headers);
+  if (Args.hasFlag(options::OPT_fmodules_validate_system_headers,
+                   options::OPT_fno_modules_validate_system_headers,
+                   ImplicitModules))
+    CmdArgs.push_back("-fmodules-validate-system-headers");
+
   Args.AddLastArg(CmdArgs, options::OPT_fmodules_disable_diagnostic_validation);
 }
 
diff --git a/clang/test/Driver/modules.m b/clang/test/Driver/modules.m
index e08de94d0e8..73db4e7e0fc 100644
--- a/clang/test/Driver/modules.m
+++ b/clang/test/Driver/modules.m
@@ -30,9 +30,15 @@
 // RUN: %clang -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS_DEFAULT %s
 // MODULES_VALIDATE_SYSTEM_HEADERS_DEFAULT-NOT: -fmodules-validate-system-headers
 
+// RUN: %clang -fmodules -fsyntax-only -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS_DEFAULT_MOD %s
+// MODULES_VALIDATE_SYSTEM_HEADERS_DEFAULT_MOD: -fmodules-validate-system-headers
+
 // RUN: %clang -fmodules-validate-system-headers -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS %s
 // MODULES_VALIDATE_SYSTEM_HEADERS: -fmodules-validate-system-headers
 
+// RUN: %clang -fno-modules-validate-system-headers -### %s 2>&1 | FileCheck -check-prefix=MODULES_VALIDATE_SYSTEM_HEADERS_NOSYSVALID %s
+// MODULES_VALIDATE_SYSTEM_HEADERS_NOSYSVALID-NOT: -fmodules-validate-system-headers
+
 // RUN: %clang -### %s 2>&1 | FileCheck -check-prefix=MODULES_DISABLE_DIAGNOSTIC_VALIDATION_DEFAULT %s
 // MODULES_DISABLE_DIAGNOSTIC_VALIDATION_DEFAULT-NOT: -fmodules-disable-diagnostic-validation