Avoid move constructor of std::fstream for GCC < 5 (#3098)

GCC < 5 does not support the move constructor of `std::fstream` (see
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54316 for details). This
commit wraps the `std::fstream` in an `std::unique_ptr` to work around
that issue.

2 files changed, 9 insertions, 4 deletions

diff --git a/src/util/utility.cpp b/src/util/utility.cpp
index 9936504d2..97d5ef36b 100644
--- a/src/util/utility.cpp
+++ b/src/util/utility.cpp
@@ -25,7 +25,7 @@
 
 namespace CVC4 {
 
-std::fstream openTmpFile(std::string* pattern)
+std::unique_ptr<std::fstream> openTmpFile(std::string* pattern)
 {
   char* tmpDir = getenv("TMPDIR");
   if (tmpDir != nullptr)
@@ -46,7 +46,7 @@ std::fstream openTmpFile(std::string* pattern)
   {
     CVC4_FATAL() << "Could not create temporary file " << *pattern;
   }
-  std::fstream tmpStream(tmpName);
+  std::unique_ptr<std::fstream> tmpStream(new std::fstream(tmpName));
   close(r);
   *pattern = std::string(tmpName);
   delete[] tmpName;
diff --git a/src/util/utility.h b/src/util/utility.h
index a606648bd..4477fc7b2 100644
--- a/src/util/utility.h
+++ b/src/util/utility.h
@@ -22,6 +22,7 @@
 #include <algorithm>
 #include <fstream>
 #include <functional>
+#include <memory>
 #include <string>
 #include <utility>
 
@@ -95,9 +96,13 @@ void container_to_stream(std::ostream& out,
  * @param pattern The filename pattern. This string is modified to contain the
  * name of the temporary file.
  *
- * @return A filestream for the temporary file.
+ * @return A unique pointer to the filestream for the temporary file.
+ *
+ * Note: We use `std::unique_ptr<std::fstream>` instead of `std::fstream`
+ * because GCC < 5 does not support the move constructor of `std::fstream`. See
+ * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54316 for details.
  */
-std::fstream openTmpFile(std::string* pattern);
+std::unique_ptr<std::fstream> openTmpFile(std::string* pattern);
 
 }/* CVC4 namespace */