[driver] Add a -builtininc flag that lets Darwin driver include Clang builtin headers even with -nostdinc

[arphaman]

Summary

Some projects use -nostdinc, but need to access some intrinsics files when building specific files. The new -builtininc flag lets them use this flag when compiling these files to ensure they can access Clang's builtin headers.

[dexonsmith]

clang/include/clang/Driver/Options.td

503–504

I think -ibuiltininc might be better, since we already have lots of options that start with -i related to include paths. Please also clarify in the HelpText that this overrules -nostdinc even if -nostdinc comes later.

clang/lib/Driver/ToolChains/Darwin.cpp

1885–1890

It's probably better to let -ibuiltininc and -nobuiltininc cancel each other out, via a "last one wins" rule. If you agree, consider documenting the behaviour also in the HelpText.

[arphaman]

Add suggested changes. The -ibuiltininc flag now interacts with -nobuiltininc as well, i.e. it's cancelled out if -nobuiltininc comes after it, and vice-versa.

[dexonsmith]

Okay, LGTM.

[MaskRay]

Should they use -nostdlibinc instead?

[arphaman]

In D73500#1846003, @MaskRay wrote:

Should they use -nostdlibinc instead?

Unfortunately they can't control the flag in this specific case, only add flags for specific files.

[MaskRay]

In D73500#1846036, @arphaman wrote:

In D73500#1846003, @MaskRay wrote:

Should they use -nostdlibinc instead?

Unfortunately they can't control the flag in this specific case, only add flags for specific files.

To make sure I understand it correctly.

There is a project using -nostdinc. It still accesses intrinsics headers, so -ibuiltininc is added to make it work. The new option requires a new release of clang. Is it really more convenient adding a new option than teaching the project to use -nostdlibinc instead of -nostdinc?

clang/include/clang/Driver/Options.td

 def allowable__client : Separate<["-"], "allowable_client">;
 def ansi : Flag<["-", "--"], "ansi">;
 def arch__errors__fatal : Flag<["-"], "arch_errors_fatal">;
 def arch : Separate<["-"], "arch">, Flags<[DriverOption]>;
 def arch__only : Separate<["-"], "arch_only">;
 def a : Joined<["-"], "a">;
 def autocomplete : Joined<["--"], "autocomplete=">;
 def bind__at__load : Flag<["-"], "bind_at_load">;
 def bundle__loader : Separate<["-"], "bundle_loader">;
 def bundle : Flag<["-"], "bundle">;
 def b : JoinedOrSeparate<["-"], "b">, Flags<[Unsupported]>;
 def cl_opt_disable : Flag<["-"], "cl-opt-disable">, Group<opencl_Group>, Flags<[CC1Option]>,
   HelpText<"OpenCL only. This option disables all optimizations. By default optimizations are enabled.">;
 def cl_strict_aliasing : Flag<["-"], "cl-strict-aliasing">, Group<opencl_Group>, Flags<[CC1Option]>,
   HelpText<"OpenCL only. This option is added for compatibility with OpenCL 1.0.">;
 def cl_single_precision_constant : Flag<["-"], "cl-single-precision-constant">, Group<opencl_Group>, Flags<[CC1Option]>,
   HelpText<"OpenCL only. Treat double precision floating-point constant as single precision constant.">;
 def cl_finite_math_only : Flag<["-"], "cl-finite-math-only">, Group<opencl_Group>, Flags<[CC1Option]>,

 def gembed_source : Flag<["-"], "gembed-source">, Group<g_flags_Group>, Flags<[CC1Option]>,
     HelpText<"Embed source text in DWARF debug sections">;
 def gno_embed_source : Flag<["-"], "gno-embed-source">, Group<g_flags_Group>,
     Flags<[DriverOption]>,
     HelpText<"Restore the default behavior of not embedding source text in DWARF debug sections">;
 def headerpad__max__install__names : Joined<["-"], "headerpad_max_install_names">;
 def help : Flag<["-", "--"], "help">, Flags<[CC1Option,CC1AsOption]>,
   HelpText<"Display available options">;
+def ibuiltininc : Flag<["-"], "ibuiltininc">,
+  HelpText<"Enable builtin #include directories even when -nostdinc is used "
+           "before or after -ibuiltininc. "
+           "Using -nobuiltininc after the option disables it">;
 def index_header_map : Flag<["-"], "index-header-map">, Flags<[CC1Option]>,
   HelpText<"Make the next included directory (-I or -F) an indexer header map">;
 def idirafter : JoinedOrSeparate<["-"], "idirafter">, Group<clang_i_Group>, Flags<[CC1Option]>,
   HelpText<"Add directory to AFTER include search path">;
 def iframework : JoinedOrSeparate<["-"], "iframework">, Group<clang_i_Group>, Flags<[CC1Option]>,
   HelpText<"Add directory to SYSTEM framework search path">;
 def iframeworkwithsysroot : JoinedOrSeparate<["-"], "iframeworkwithsysroot">,
   Group<clang_i_Group>,

clang/lib/Driver/ToolChains/Darwin.cpp

 void DarwinClang::AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                                             llvm::opt::ArgStringList &CC1Args) const {
   const Driver &D = getDriver();
 
   llvm::StringRef Sysroot = GetHeaderSysroot(DriverArgs);
 
   bool NoStdInc = DriverArgs.hasArg(options::OPT_nostdinc);
   bool NoStdlibInc = DriverArgs.hasArg(options::OPT_nostdlibinc);
-  bool NoBuiltinInc = DriverArgs.hasArg(options::OPT_nobuiltininc);
+  bool NoBuiltinInc = DriverArgs.hasFlag(
+      options::OPT_nobuiltininc, options::OPT_ibuiltininc, /*Default=*/false);
+  bool ForceBuiltinInc = DriverArgs.hasFlag(
+      options::OPT_ibuiltininc, options::OPT_nobuiltininc, /*Default=*/false);
 
   // Add <sysroot>/usr/local/include
   if (!NoStdInc && !NoStdlibInc) {
       SmallString<128> P(Sysroot);
       llvm::sys::path::append(P, "usr", "local", "include");
       addSystemInclude(DriverArgs, CC1Args, P);
   }
 
   // Add the Clang builtin headers (<resource>/include)
-  if (!NoStdInc && !NoBuiltinInc) {
+  if (!(NoStdInc && !ForceBuiltinInc) && !NoBuiltinInc) {
     SmallString<128> P(D.ResourceDir);
     llvm::sys::path::append(P, "include");
     addSystemInclude(DriverArgs, CC1Args, P);
   }
 
   if (NoStdInc || NoStdlibInc)
     return;
 
   // Check for configure-time C include directories.
   llvm::StringRef CIncludeDirs(C_INCLUDE_DIRS);
   if (!CIncludeDirs.empty()) {
     llvm::SmallVector<llvm::StringRef, 5> dirs;

clang/test/Driver/darwin-header-search-system.cpp

 // RUN:     -ccc-install-dir %S/Inputs/basic_darwin_toolchain_no_libcxx/usr/bin \
 // RUN:     -resource-dir=%S/Inputs/resource_dir \
 // RUN:   | FileCheck -DRESOURCE=%S/Inputs/resource_dir \
 // RUN:               --check-prefix=CHECK-NOSYSROOT %s
 // CHECK-NOSYSROOT: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
 // CHECK-NOSYSROOT: "-internal-isystem" "/usr/local/include"
 // CHECK-NOSYSROOT: "-internal-isystem" "[[RESOURCE]]/include"
 // CHECK-NOSYSROOT: "-internal-externc-isystem" "/usr/include"
+
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-apple-darwin \
+// RUN:     -ccc-install-dir %S/Inputs/basic_darwin_toolchain_no_libcxx/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     -isysroot %S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:     -nostdinc -ibuiltininc \
+// RUN:   | FileCheck -DSYSROOT=%S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:               -DRESOURCE=%S/Inputs/resource_dir \
+// RUN:               --check-prefix=CHECK-NOSTDINC-BUILTINC %s
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-apple-darwin \
+// RUN:     -ccc-install-dir %S/Inputs/basic_darwin_toolchain_no_libcxx/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     -isysroot %S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:     -ibuiltininc -nostdinc \
+// RUN:   | FileCheck -DSYSROOT=%S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:               -DRESOURCE=%S/Inputs/resource_dir \
+// RUN:               --check-prefix=CHECK-NOSTDINC-BUILTINC %s
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-apple-darwin \
+// RUN:     -ccc-install-dir %S/Inputs/basic_darwin_toolchain_no_libcxx/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     -isysroot %S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:     -nostdinc -nobuiltininc -ibuiltininc \
+// RUN:   | FileCheck -DSYSROOT=%S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:               -DRESOURCE=%S/Inputs/resource_dir \
+// RUN:               --check-prefix=CHECK-NOSTDINC-BUILTINC %s
+// CHECK-NOSTDINC-BUILTINC: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
+// CHECK-NOSTDINC-BUILTINC-NOT: "-internal-isystem" "[[SYSROOT]]/usr/local/include"
+// CHECK-NOSTDINC-BUILTINC: "-internal-isystem" "[[RESOURCE]]/include"
+// CHECK-NOSTDINC-BUILTINC-NOT: "-internal-externc-isystem" "[[SYSROOT]]/usr/include"
+
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-apple-darwin \
+// RUN:     -ccc-install-dir %S/Inputs/basic_darwin_toolchain_no_libcxx/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     -isysroot %S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:     -nobuiltininc -ibuiltininc \
+// RUN:   | FileCheck -DSYSROOT=%S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:               -DRESOURCE=%S/Inputs/resource_dir \
+// RUN:               --check-prefix=CHECK-NOBUILTININC-BUILTINC %s
+// CHECK-NOBUILTININC-BUILTINC: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
+// CHECK-NOBUILTININC-BUILTINC: "-internal-isystem" "[[SYSROOT]]/usr/local/include"
+// CHECK-NOBUILTININC-BUILTINC: "-internal-isystem" "[[RESOURCE]]/include"
+// CHECK-NOBUILTININC-BUILTINC: "-internal-externc-isystem" "[[SYSROOT]]/usr/include"
+
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-apple-darwin \
+// RUN:     -ccc-install-dir %S/Inputs/basic_darwin_toolchain_no_libcxx/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     -isysroot %S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:     -nostdinc -ibuiltininc -nobuiltininc \
+// RUN:   | FileCheck -DSYSROOT=%S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:               -DRESOURCE=%S/Inputs/resource_dir \
+// RUN:               --check-prefix=CHECK-NOSTDINC-NO-BUILTINC %s
+// CHECK-NOSTDINC-NO-BUILTINC: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
+// CHECK-NOSTDINC-NO-BUILTINC-NOT: "-internal-isystem" "[[SYSROOT]]/usr/local/include"
+// CHECK-NOSTDINC-NO-BUILTINC-NOT: "-internal-isystem" "[[RESOURCE]]/include"
+// CHECK-NOSTDINC-NO-BUILTINC-NOT: "-internal-externc-isystem" "[[SYSROOT]]/usr/include"
+
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-apple-darwin \
+// RUN:     -ccc-install-dir %S/Inputs/basic_darwin_toolchain_no_libcxx/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     -isysroot %S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:     -ibuiltininc -nobuiltininc \
+// RUN:   | FileCheck -DSYSROOT=%S/Inputs/basic_darwin_sdk_usr_and_usr_local \
+// RUN:               -DRESOURCE=%S/Inputs/resource_dir \
+// RUN:               --check-prefix=CHECK-BUILTINC-NOBUILTININC %s
+// CHECK-BUILTINC-NOBUILTININC: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
+// CHECK-BUILTINC-NOBUILTININC: "-internal-isystem" "[[SYSROOT]]/usr/local/include"
+// CHECK-BUILTINC-NOBUILTININC-NOT: "-internal-isystem" "[[RESOURCE]]/include"
+// CHECK-BUILTINC-NOBUILTININC: "-internal-externc-isystem" "[[SYSROOT]]/usr/include"