fix Issue 14464 - coverage merge doesn't work

posix.mak

@@ -193,7 +193,7 @@ $(DRUNTIME): $(OBJS) $(SRCS)
 UT_MODULES:=$(patsubst src/%.d,$(OBJDIR)/%,$(SRCS))
 HAS_ADDITIONAL_TESTS:=$(shell test -d test && echo 1)
 ifeq ($(HAS_ADDITIONAL_TESTS),1)
-	ADDITIONAL_TESTS:=test/init_fini test/exceptions
+	ADDITIONAL_TESTS:=test/init_fini test/exceptions test/coverage
 	ADDITIONAL_TESTS+=$(if $(SHARED),test/shared,)
 endif
 

src/core/runtime.d

@@ -314,12 +314,37 @@ struct Runtime
 
 
 private:
+
     // NOTE: This field will only ever be set in a static ctor and should
     //       never occur within any but the main thread, so it is safe to
     //       make it __gshared.
     __gshared ModuleUnitTester sm_moduleUnitTester = null;
 }
 
+/**
+ * Set source file path for coverage reports.
+ *
+ * Params:
+ *  path = The new path name.
+ */
+extern (C) void dmd_coverSourcePath(string path);
+
+/**
+ * Set output path for coverage reports.
+ *
+ * Params:
+ *  path = The new path name.
+ */
+extern (C) void dmd_coverDestPath(string path);
+
+/**
+ * Enable merging of coverage reports with existing data.
+ *
+ * Params:
+ *  merge = enable/disable coverage merge mode
+ */
+extern (C) void dmd_coverSetMerge(bool flag);
+
 ///////////////////////////////////////////////////////////////////////////////
 // Overridable Callbacks
 ///////////////////////////////////////////////////////////////////////////////