Fix use-after-frees in unix_platform.hpp

Author: akalin

backend/src/unix_platform.hpp

@@ -61,7 +61,9 @@ class UnixPlatform : public AbstractPlatform
     int err;
     struct stat file_stat;
 
-    err = stat(this->path().c_str(), &file_stat);
+    const string &path = this->path();
+
+    err = stat(path.c_str(), &file_stat);
     if (err == -1)
       throw runtime_error("stat() failed");
 
@@ -75,10 +77,10 @@ class UnixPlatform : public AbstractPlatform
     int err;
     int fd;
 
-    const char *path = this->path().c_str();
+    const string &path = this->path();
 
     // Open the file.
-    fd = open(path, O_RDONLY, 0);
+    fd = open(path.c_str(), O_RDONLY, 0);
     if (fd < 0)
       throw runtime_error(str(boost::format("fix_permissions: open() failed: %d.") % errno));