Implement ability to compile directly from stdin

Author: vanceism7

source/common.h

@@ -799,7 +799,9 @@ class cmdline_processor
             [](auto& a, auto& b){ return a.group < b.group || (a.group == b.group && a.name < b.name); }
         );
 
-        print("\nUsage: cppfront [options] file ...\n\nOptions:\n");
+        print("\nUsage: cppfront [options] file ...\n");
+        print("\nfile - The source file(s) to compile (can be 'stdin' to read text directly) \n");
+        print("\nOptions: \n");
         int last_group = -1;
         for (auto& flag : flags) {
             //  Skip hidden flags

source/cppfront.cpp

@@ -84,7 +84,12 @@ auto main(
         }
 
         //  Load + lex + parse + sema
-        cppfront c(arg.text);
+        cppfront c = [&]() -> cppfront {
+            if (arg.text == "stdin") 
+                return cppfront(std::cin);
+            else
+                return cppfront(arg.text);
+        }();
 
         //  Generate Cpp1 (this may catch additional late errors)
         auto count = c.lower_to_cpp1();

source/io.h

@@ -887,6 +887,20 @@ class source
             return false;
         }
 
+        return load(in);
+    }
+
+    //-----------------------------------------------------------------------
+    //  load: Read a line-by-line view of a source file, preserving line breaks
+    //
+    //  in                      the loaded source file
+    //  source                  program textual representation
+    //
+    auto load(
+        std::istream&  in
+    )
+        -> bool
+    {
         auto in_comment            = false;
         auto in_string_literal     = false;
         auto in_raw_string_literal = false;

source/to_cpp1.h

@@ -1202,37 +1202,73 @@ class cppfront
 
         else
         {
-            //  Tokenize
-            //
-            tokens.lex(source.get_lines());
-
-            //  Parse
-            //
-            try
-            {
-                for (auto const& [line, entry] : tokens.get_map()) {
-                    if (!parser.parse(entry, tokens.get_generated())) {
-                        errors.emplace_back(
-                            source_position(line, 0),
-                            "parse failed for section starting here",
-                            false,
-                            true    // a noisy fallback error message
-                        );
-                    }
-                }
+            process_cpp2();
+        }
+    }
 
-                //  Sema
-                parser.visit(sema);
-                if (!sema.apply_local_rules()) {
-                    violates_initialization_safety = true;
-                }
-            }
-            catch (std::runtime_error& e) {
+    //-----------------------------------------------------------------------
+    //  Constructor
+    //
+    //  source_stream    the contents of a source file to be processed
+    //
+    cppfront(std::istream& source_stream)
+        : sourcefile{ "stdin.cpp2" }
+        , source    { errors }
+        , tokens    { errors }
+        , parser    { errors, includes }
+        , sema      { errors }
+    {
+        //  Load the program file into memory
+        //
+        if (!source.load(source_stream))
+        {
+            if (errors.empty()) {
                 errors.emplace_back(
                     source_position(-1, -1),
-                    e.what()
+                    "error reading source content from stdin"
                 );
             }
+            source_loaded = false;
+        }
+
+        else
+        {
+            process_cpp2();
+        }
+    }
+
+    auto process_cpp2() -> void
+    {
+        //  Tokenize
+        //
+        tokens.lex(source.get_lines());
+
+        //  Parse
+        //
+        try
+        {
+            for (auto const& [line, entry] : tokens.get_map()) {
+                if (!parser.parse(entry, tokens.get_generated())) {
+                    errors.emplace_back(
+                        source_position(line, 0),
+                        "parse failed for section starting here",
+                        false,
+                        true    // a noisy fallback error message
+                    );
+                }
+            }
+
+            //  Sema
+            parser.visit(sema);
+            if (!sema.apply_local_rules()) {
+                violates_initialization_safety = true;
+            }
+        }
+        catch (std::runtime_error& e) {
+            errors.emplace_back(
+                source_position(-1, -1),
+                e.what()
+            );
         }
     }