Add comments about putenv() usage

Again thanks to Enrico.

diff --git a/src/support/environment.cpp b/src/support/environment.cpp
index a3539220d9457832b2b117cc21b48014ed307112..ac5729bd977641b4739cc6c9eb4499c97022de96 100644 (file)
--- a/src/support/environment.cpp
+++ b/src/support/environment.cpp
@@ -71,6 +71,10 @@ bool setEnv(string const & name, string const & value)
 #if defined (HAVE_SETENV)
        return ::setenv(name.c_str(), encoded.c_str(), 1) == 0;
 #elif defined (HAVE_PUTENV)
+       // According to http://pubs.opengroup.org/onlinepubs/9699919799/functions/putenv.html
+       // the argument of putenv() needs to be static, because changing its
+       // value will change the environment. Therefore we need a different static
+       // storage for each variable.
        static map<string, string> varmap;
        varmap[name] = name + '=' + encoded;
        return ::putenv(const_cast<char*>(varmap[name].c_str())) == 0;
@@ -132,6 +136,8 @@ bool unsetEnv(string const & name)
        return ::unsetenv(name.c_str()) == 0;
 #elif defined(HAVE_PUTENV)
        // This is OK with MSVC and MinGW at least.
+       // FIXME: According to http://pubs.opengroup.org/onlinepubs/9699919799/functions/putenv.html
+       //        the argument of putenv() needs to be static, see setEnv().
        return ::putenv(const_cast<char*>((name + "=").c_str())) == 0;
 #else
 #error No environment-unsetting function has been defined.