Add some scaffolding needed for C++ modules in GCC.

Further work pending GCC bug #105467 and/or Ninja bug #1962.

mesonbuild/backend/ninjabackend.py

@@ -913,6 +913,8 @@ class NinjaBackend(backends.Backend):
             return True
         if 'cpp' not in target.compilers:
             return False
+        if '-fmodules-ts' in target.extra_args.get('cpp', []):
+            return True
         # Currently only the preview version of Visual Studio is supported.
         cpp = target.compilers['cpp']
         if cpp.get_id() != 'msvc':

test cases/unit/85 cpp modules/gcc/main.cpp

@@ -0,0 +1,7 @@
+import M0;
+#include<cstdio>
+
+int main() {
+    printf("The value is %d", func0());
+    return 0;
+}

test cases/unit/85 cpp modules/gcc/meson.build

@@ -0,0 +1,19 @@
+# GCC does not recognize .ixx as a C++ source extension so
+# we have to do this instead.
+
+e = executable('modtest',
+    'main.cpp',
+    'src0.cxx',
+    'src1.cxx',
+    'src2.cxx',
+    'src3.cxx',
+    'src4.cxx',
+    'src5.cxx',
+    'src6.cxx',
+    'src7.cxx',
+    'src8.cxx',
+    'src9.cxx',
+    cpp_args: ['-fmodules-ts'],
+    )
+
+test('modtest', e)

test cases/unit/85 cpp modules/gcc/src0.cxx

@@ -0,0 +1,7 @@
+export module M0;
+
+import M1;
+
+export int func0() {
+  return func1();
+}

test cases/unit/85 cpp modules/gcc/src1.cxx

@@ -0,0 +1,7 @@
+export module M1;
+
+import M2;
+
+export int func1() {
+  return func2();
+}

test cases/unit/85 cpp modules/gcc/src2.cxx

@@ -0,0 +1,7 @@
+export module M2;
+
+import M3;
+
+export int func2() {
+  return func3();
+}

test cases/unit/85 cpp modules/gcc/src3.cxx

@@ -0,0 +1,7 @@
+export module M3;
+
+import M4;
+
+export int func3() {
+  return func4();
+}

test cases/unit/85 cpp modules/gcc/src4.cxx

@@ -0,0 +1,7 @@
+export module M4;
+
+import M5;
+
+export int func4() {
+  return func5();
+}

test cases/unit/85 cpp modules/gcc/src5.cxx

@@ -0,0 +1,7 @@
+export module M5;
+
+import M6;
+
+export int func5() {
+  return func6();
+}

test cases/unit/85 cpp modules/gcc/src6.cxx

@@ -0,0 +1,7 @@
+export module M6;
+
+import M7;
+
+export int func6() {
+  return func7();
+}

test cases/unit/85 cpp modules/gcc/src7.cxx

@@ -0,0 +1,7 @@
+export module M7;
+
+import M8;
+
+export int func7() {
+  return func8();
+}

test cases/unit/85 cpp modules/gcc/src8.cxx

@@ -0,0 +1,7 @@
+export module M8;
+
+import M9;
+
+export int func8() {
+  return func9();
+}

test cases/unit/85 cpp modules/gcc/src9.cxx

@@ -0,0 +1,5 @@
+export module M9;
+
+export int func9() {
+  return 42;
+}

test cases/unit/85 cpp modules/meson.build

@@ -4,6 +4,8 @@ cpp = meson.get_compiler('cpp')
 
 if cpp.get_id() == 'msvc'
     subdir('vs')
+elif cpp.get_id() == 'gcc'
+    subdir('gcc')
 else
     error('Unknown compiler')
 endif