Wrapped variables in conditions

This allows CXX and CXXFLAGS to be overridden without patching. Added PREFIX for MacPorts compatibility, allowing staging to $(DESTDIR)$(PREFIX)/bin, leaving original behaviour unchanged.

Exit early if run in incorrect directory or if Makefile cannot be written.

tools/dmake.cpp

@@ -98,6 +98,16 @@ static void getCppFiles(std::vector<std::string> &files, const std::string &path
     }
 }
 
+
+static void makeConditionalVariable(std::ostream &os, const std::string &variable, const std::string &value)
+{
+    os << "ifndef " << variable << '\n'
+       << "    " << variable << '=' << value << '\n'
+       << "endif\n"
+       << "\n";
+}
+
+
 int main(int argc, char **argv)
 {
     const bool release(argc >= 2 && std::string(argv[1]) == "--release");
@@ -112,6 +122,12 @@ int main(int argc, char **argv)
     std::vector<std::string> testfiles;
     getCppFiles(testfiles, "test/");
 
+    if (libfiles.empty() && clifiles.empty() && testfiles.empty())
+    {
+        std::cerr << "No files found. Are you in the correct directory?" << std::endl;
+        return EXIT_FAILURE;
+    }
+
 
     // QMAKE - lib/lib.pri
     {
@@ -142,35 +158,46 @@ int main(int argc, char **argv)
     }
 
 
-    std::ofstream fout("Makefile");
+    static const char makefile[] = "Makefile";
+    std::ofstream fout(makefile, std::ios_base::trunc);
+    if (!fout.is_open())
+    {
+        std::cerr << "An error occurred while trying to open "
+                  << makefile
+                  << ".\n";
+        return EXIT_FAILURE;
+    }
 
     // Makefile settings..
     if (release)
     {
-        fout << "CXXFLAGS=-O2 -DNDEBUG -Wall\n";
+        makeConditionalVariable(fout, "CXXFLAGS", "-O2 -DNDEBUG -Wall");
     }
     else
     {
+        fout << "# This file is generated by tools/dmake, do not edit.\n\n";
+
         // TODO: add more compiler warnings.
         // -Wconversion      : generates too many compiler warnings currently
         // -Wlogical-op      : doesn't work on older GCC
 
         // The _GLIBCXX_DEBUG doesn't work in cygwin
-        fout << "CXXFLAGS="
-             << "-Wall "
-             << "-Wextra "
-             << "-Wshadow "
-             << "-pedantic "
-             << "-Wno-long-long "
-             << "-Wfloat-equal "
-             << "-Wcast-qual "
-             << "-Wsign-conversion "
-             // << "-Wconversion "
-             << "-g\n";
+        makeConditionalVariable(fout, "CXXFLAGS",
+                                "-Wall "
+                                "-Wextra "
+                                "-Wshadow "
+                                "-pedantic "
+                                "-Wno-long-long "
+                                "-Wfloat-equal "
+                                "-Wcast-qual "
+                                "-Wsign-conversion "
+                                // "-Wconversion "
+                                "-g");
     }
-    fout << "CXX=g++\n";
-    fout << "BIN=${DESTDIR}/usr/bin\n\n";
-    fout << "# For 'make man': sudo apt-get install xsltproc docbook-xsl docbook-xml\n";
+    makeConditionalVariable(fout, "CXX", "g++");
+    makeConditionalVariable(fout, "PREFIX", "/usr");
+    fout << "BIN=$(DESTDIR)$(PREFIX)/bin\n\n";
+    fout << "# For 'make man': sudo apt-get install xsltproc docbook-xsl docbook-xml on Linux\n";
     fout << "DB2MAN=/usr/share/sgml/docbook/stylesheet/xsl/nwalsh/manpages/docbook.xsl\n";
     fout << "XP=xsltproc -''-nonet -''-param man.charmap.use.subset \"0\"\n";
     fout << "MAN_SOURCE=man/cppcheck.1.xml\n\n";
@@ -221,4 +248,3 @@ int main(int argc, char **argv)
     return 0;
 }
 
-