Optimize handling of --append=<file> option (execution time, memory)

Whitespace was removed from the append data for every configuration
and every file: n(configuration) * n(files).

Removing whitespace immediately after the append data was read can
significantly reduce the execution time and memory usage.
It also allows further improvement because copies to the temporary
object appendCode are no longer needed.

Signed-off-by: Stefan Weil <sw@weilnetz.de>

lib/cppcheck.cpp

@@ -234,9 +234,7 @@ unsigned int CppCheck::processFile()
                 _errorLogger.reportOut(std::string("Checking ") + fixedpath + ": " + cfg + std::string("..."));
             }
 
-            std::string appendCode = _settings.append();
-            if (!appendCode.empty())
-                Preprocessor::preprocessWhitespaces(appendCode);
+            const std::string &appendCode = _settings.append();
 
             if (_settings.debugFalsePositive) {
                 if (findError(codeWithoutCfg + appendCode, _filename.c_str())) {

lib/settings.cpp

@@ -18,6 +18,7 @@
 
 #include "settings.h"
 #include "path.h"
+#include "preprocessor.h"       // Preprocessor
 
 #include <fstream>
 #include <set>
@@ -129,10 +130,11 @@ bool Settings::append(const std::string &filename)
     while (std::getline(fin, line)) {
         _append += line + "\n";
     }
+    Preprocessor::preprocessWhitespaces(_append);
     return true;
 }
 
-std::string Settings::append() const
+const std::string &Settings::append() const
 {
     return _append;
 }

lib/settings.h

@@ -119,7 +119,7 @@ public:
     bool append(const std::string &filename);
 
     /** @brief get append code (--append) */
-    std::string append() const;
+    const std::string &append() const;
 
     /** @brief Maximum number of configurations to check before bailing.
         Default is 12. (--max-configs=N) */