bugfix: avoid naive use of 'putenv' by providing 'FbTk::App::setenv()'

to quote from 'man putenv':

   The string pointed to by string becomes part of the environment,
   so altering the string changes the environment.

so, using putenv like

   {
      std::string foo("FOO=bar");
      putenv(foo.c_str());
   }

is wrong and leads to a potentially corrupted environment. valgrind
complaint correctly.

FbTk::App seems to be the appropriate place to hold '::seten()'
because it alters the environment of the application.

2 files changed, 60 insertions, 0 deletions

diff --git a/src/FbTk/App.cc b/src/FbTk/App.cc
index 39cd36e..8157839 100644
--- a/src/FbTk/App.cc
+++ b/src/FbTk/App.cc
@@ -26,6 +26,21 @@
 
 #include "EventManager.hh"
 
+#ifdef HAVE_CSTRING
+  #include <cstring>
+#else
+  #include <string.h>
+#endif
+#ifdef HAVE_CSTDLIB
+  #include <cstdlib>
+#else
+  #include <stdlib.h>
+#endif
+
+
+#include <set>
+
+
 namespace FbTk {
 
 App *App::s_app = 0;
@@ -79,4 +94,44 @@ void App::end() {
     m_done = true; //end loop in App::eventLoop
 }
 
+bool App::setenv(const char* key, const char* value) {
+
+    if (!key || !*key)
+        return false;
+
+    static std::set<char*> stored;
+
+    const size_t key_size = strlen(key);
+    const size_t value_size = value ? strlen(value) : 0;
+
+    char* newenv = new char[key_size + value_size + 2];
+    if (newenv) {
+
+        char* oldenv = getenv(key);
+
+        // oldenv points to the value .. we have to go back a bit
+        if (oldenv && stored.find(oldenv - (key_size + 1)) != stored.end())
+            oldenv -= (key_size + 1);
+        else
+            oldenv = NULL;
+
+        memset(newenv, 0, key_size + value_size + 2);
+        strcat(newenv, key);
+        strcat(newenv, "=");
+        if (value_size > 0)
+            strcat(newenv, value);
+
+        if (putenv(newenv) == 0) {
+            if (oldenv) {
+                stored.erase(oldenv);
+                delete[] oldenv;
+            }
+            stored.insert(newenv);
+        }
+        return true;
+    }
+
+    return false;
+}
+
 } // end namespace FbTk
diff --git a/src/FbTk/App.hh b/src/FbTk/App.hh
index d878661..b83dd15 100644
--- a/src/FbTk/App.hh
+++ b/src/FbTk/App.hh
@@ -53,6 +53,11 @@ public:
     /// forces an end to event loop
     void end();
     bool done() const { return m_done; }
+
+    // the setenv()-routine is not everywhere available and
+    // putenv() doesnt manage the strings in the environment
+    // and hence we have to do that on our own to avoid memleaking
+    static bool setenv(const char* key, const char* value);
 private:
     static App *s_app;
     bool m_done;