Here are the new options, along with the C++ lang-spec changes.
Modules is enabled by -fmodules-ts, it is not implicitly enabled by
-std=c++20. Usually that's the only option you need to add for a
module-aware build.
to build a header unit you can either add -fmodule-header to a c++
build, or you can set the language to be c++-header and add -fmodules-ts:
g++ -x c++-header -fmodules-ts my-header-file
to search the user or system include paths select c++-user-header of
c++-system-header as the language.
enabling -fmodules-ts will disable PCH, they do not play well together.
There is a potential issue down the road when we implicitly enable
modules. At that point building a header-unit could become
indistinguishable from building a PCH. Perhaps we should consider
phasing in an explicit PCH option?
--
Nathan Sidwell
diff --git c/gcc/c-family/c-opts.c w/gcc/c-family/c-opts.c
index 120f4489f6c..c8f08d9e014 100644
--- c/gcc/c-family/c-opts.c
+++ w/gcc/c-family/c-opts.c
@@ -234,6 +234,7 @@ c_common_init_options (unsigned int decoded_options_count,
cpp_opts = cpp_get_options (parse_in);
cpp_opts->dollars_in_ident = DOLLARS_IN_IDENTIFIERS;
cpp_opts->objc = c_dialect_objc ();
+ cpp_opts->deps.modules = true;
/* Reset to avoid warnings on internal definitions. We set it just
before passing on command-line options to cpplib. */
@@ -367,6 +368,18 @@ c_common_handle_option (size_t scode, const char *arg, HOST_WIDE_INT value,
cpp_opts->deps.phony_targets = true;
break;
+ case OPT_Mmodules:
+ /* Do not set deps_seen, so the user can unconditionally turn
+ this on or off. */
+ cpp_opts->deps.modules = true;
+ break;
+
+ case OPT_Mno_modules:
+ /* Do not set deps_seen, so the user can unconditionally turn
+ this on or off. */
+ cpp_opts->deps.modules = false;
+ break;
+
case OPT_MQ:
case OPT_MT:
deps_seen = true;
diff --git c/gcc/c-family/c-pch.c w/gcc/c-family/c-pch.c
index a2292f46a7d..f55a1fde3ad 100644
--- c/gcc/c-family/c-pch.c
+++ w/gcc/c-family/c-pch.c
@@ -206,6 +206,10 @@ c_common_valid_pch (cpp_reader *pfile, const char *name, int fd)
/* Perform a quick test of whether this is a valid
precompiled header for the current language. */
+ /* C++ modules and PCH don't play together. */
+ if (flag_modules)
+ return 2;
+
sizeread = read (fd, ident, IDENT_LENGTH + 16);
if (sizeread == -1)
fatal_error (input_location, "cannot read %s: %m", name);
diff --git c/gcc/c-family/c.opt w/gcc/c-family/c.opt
index 10e53ea67c9..1edc7f2b2bd 100644
--- c/gcc/c-family/c.opt
+++ w/gcc/c-family/c.opt
@@ -236,6 +236,14 @@ MMD
C ObjC C++ ObjC++ NoDriverArg Separate MissingArgError(missing filename after %qs)
Like -MD but ignore system header files.
+Mmodules
+C++
+Generate C++ Module dependency information.
+
+Mno-modules
+C++
+; undocumented
+
MP
C ObjC C++ ObjC++
Generate phony targets for all headers.
@@ -1666,6 +1674,53 @@ flax-vector-conversions
C ObjC C++ ObjC++ Var(flag_lax_vector_conversions)
Allow implicit conversions between vectors with differing numbers of subparts and/or differing element types.
+fmodules-ts
+C++ ObjC++ Var(flag_modules) Integer Init(0)
+Enable C++ modules-ts (experimental).
+
+fno-modules
+C++ ObjC++ Undocumented RejectNegative Var(flag_modules,0) Integer
+;; undocumented
+
+fmodule-header
+C++ ObjC RejectNegative Var(flag_header_unit,0) Integer
+Enable C++ header module (experimental).
+
+fmodule-header=
+C++ ObjC++ Joined RejectNegative Undocumented
+
+fmodule-implicit-inline
+C++ ObjC++ Var(flag_module_implicit_inline,0) Integer
+Member functions defined within their class are inline in module purview.
+
+fmodule-only
+C++ ObjC RejectNegative Var(flag_module_only) Integer
+Only emit Binary Module Interface.
+
+fmodule-mapper=
+C++ ObjC++ Joined RejectNegative MissingArgError(missing mapper)
+Mapper for module to CMI files.
+
+fmodule-lazy
+C++ ObjC++ Var(flag_module_lazy) Init(1)
+Enable lazy module importing.
+
+fmodule-version-ignore
+C++ ObjC Var(flag_module_version_ignore) Integer
+; undocumented, Very dangerous, but occasionally useful
+
+Winvalid-imported-macros
+C++ ObjC++ Var(warn_imported_macros)
+Warn about macros that have conflicting header units definitions.
+
+flang-info-include-translate
+C++ Var(note_include_translate)
+Note #include directives translated to import declarations.
+
+flang-info-include-translate=
+C++ Joined RejectNegative MissingArgError(missing header name)
+Note a #include translation of a specific header.
+
fmax-include-depth=
C ObjC C++ ObjC++ Joined RejectNegative UInteger
fmax-include-depth=<number> Set the maximum depth of the nested #include.
diff --git c/gcc/cp/lang-specs.h w/gcc/cp/lang-specs.h
index 0ad4a33b93e..1388aaed198 100644
--- c/gcc/cp/lang-specs.h
+++ w/gcc/cp/lang-specs.h
@@ -40,17 +40,57 @@ along with GCC; see the file COPYING3. If not see
{".tcc", "@c++-header", 0, 0, 0},
{".hh", "@c++-header", 0, 0, 0},
{"@c++-header",
- "%{E|M|MM:cc1plus -E %(cpp_options) %2 %(cpp_debug_options)}"
+ "%{E|M|MM:cc1plus -E %{fmodules-ts:-fdirectives-only -fmodule-header}"
+ " %(cpp_options) %2 %(cpp_debug_options)}"
+ "%{!E:%{!M:%{!MM:"
+ " %{save-temps*|no-integrated-cpp:cc1plus -E"
+ " %{fmodules-ts:-fdirectives-only -fmodule-header}"
+ " %(cpp_options) %2 -o %{save-temps*:%b.ii} %{!save-temps*:%g.ii} \n}"
+ " cc1plus %{save-temps*|no-integrated-cpp:-fpreprocessed"
+ " %{fmodules-ts:-fdirectives-only}"
+ " %{save-temps*:%b.ii} %{!save-temps*:%g.ii}}"
+ " %{!save-temps*:%{!no-integrated-cpp:%(cpp_unique_options)}}"
+ " %{fmodules-ts:-fmodule-header %{fpreprocessed:-fdirectives-only}}"
+ " %(cc1_options) %2"
+ " %{!S:-o %g.s%V}"
+ " %{!fsyntax-only:%{!fmodule-*:%{!fmodules-*:%{!fdump-ada-spec*:"
+ " %{!o*:--output-pch=%i.gch}%W{o*:--output-pch=%*}}}}}}}}",
+ CPLUSPLUS_CPP_SPEC, 0, 0},
+ {"@c++-system-header",
+ "%{E|M|MM:cc1plus -E"
+ " %{fmodules-ts:-fdirectives-only -fmodule-header=system}"
+ " %(cpp_options) %2 %(cpp_debug_options)}"
"%{!E:%{!M:%{!MM:"
" %{save-temps*|no-integrated-cpp:cc1plus -E"
+ " %{fmodules-ts:-fdirectives-only -fmodule-header=system}"
" %(cpp_options) %2 -o %{save-temps*:%b.ii} %{!save-temps*:%g.ii} \n}"
" cc1plus %{save-temps*|no-integrated-cpp:-fpreprocessed"
+ " %{fmodules-ts:-fdirectives-only}"
" %{save-temps*:%b.ii} %{!save-temps*:%g.ii}}"
" %{!save-temps*:%{!no-integrated-cpp:%(cpp_unique_options)}}"
+ " %{fmodules-ts:-fmodule-header=system %{fpreprocessed:-fdirectives-only}}"
" %(cc1_options) %2"
- " %{!fsyntax-only:%{!S:-o %g.s}"
- " %{!fdump-ada-spec*:%{!o*:--output-pch=%i.gch}"
- " %W{o*:--output-pch=%*}}%V}}}}",
+ " %{!S:-o %g.s%V}"
+ " %{!fsyntax-only:%{!fmodule-*:%{!fmodules-*:%{!fdump-ada-spec*:"
+ " %{!o*:--output-pch=%i.gch}%W{o*:--output-pch=%*}}}}}}}}",
+ CPLUSPLUS_CPP_SPEC, 0, 0},
+ {"@c++-user-header",
+ "%{E|M|MM:cc1plus -E"
+ " %{fmodules-ts:-fdirectives-only -fmodule-header=user}"
+ " %(cpp_options) %2 %(cpp_debug_options)}"
+ "%{!E:%{!M:%{!MM:"
+ " %{save-temps*|no-integrated-cpp:cc1plus -E"
+ " %{fmodules-ts:-fdirectives-only -fmodule-header=user}"
+ " %(cpp_options) %2 -o %{save-temps*:%b.ii} %{!save-temps*:%g.ii} \n}"
+ " cc1plus %{save-temps*|no-integrated-cpp:-fpreprocessed"
+ " %{fmodules-ts:-fdirectives-only}"
+ " %{save-temps*:%b.ii} %{!save-temps*:%g.ii}}"
+ " %{!save-temps*:%{!no-integrated-cpp:%(cpp_unique_options)}}"
+ " %{fmodules-ts:-fmodule-header=user %{fpreprocessed:-fdirectives-only}}"
+ " %(cc1_options) %2"
+ " %{!S:-o %g.s%V}"
+ " %{!fsyntax-only:%{!fmodule-*:%{!fmodules-*:%{!fdump-ada-spec*:"
+ " %{!o*:--output-pch=%i.gch}%W{o*:--output-pch=%*}}}}}}}}",
CPLUSPLUS_CPP_SPEC, 0, 0},
{"@c++",
"%{E|M|MM:cc1plus -E %(cpp_options) %2 %(cpp_debug_options)}"
@@ -60,11 +100,14 @@ along with GCC; see the file COPYING3. If not see
" cc1plus %{save-temps*|no-integrated-cpp:-fpreprocessed"
" %{save-temps*:%b.ii} %{!save-temps*:%g.ii}}"
" %{!save-temps*:%{!no-integrated-cpp:%(cpp_unique_options)}}"
- " %(cc1_options) %2"
- " %{!fsyntax-only:%(invoke_as)}}}}",
+ " %(cc1_options) %2"
+ " %{fmodule-only:%{!S:-o %g.s%V}}"
+ " %{!fsyntax-only:%{!fmodule-only:%(invoke_as)}}}}}",
CPLUSPLUS_CPP_SPEC, 0, 0},
{".ii", "@c++-cpp-output", 0, 0, 0},
{"@c++-cpp-output",
"%{!E:%{!M:%{!MM:"
" cc1plus -fpreprocessed %i %(cc1_options) %2"
- " %{!fsyntax-only:%(invoke_as)}}}}", 0, 0, 0},
+ " %{fmodule-only:%{!S:-o %g.s%V}}"
+ " %{!fsyntax-only:%{!fmodule-only:%{!fmodule-header*:"
+ " %(invoke_as)}}}}}}", 0, 0, 0},
