[Spice-devel] [PATCH spice-streaming-server v2 1/3] Use defer style destruction instead of old C style and goto

[Frediano Ziglio]

This better integrate with exceptions.
Also don't leak resources using a return in the middle of the
code.

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 src/Makefile.am               |  1 +
 src/defer.hpp                 | 16 ++++++++++++++++
 src/spice-streaming-agent.cpp | 18 ++++++++++--------
 3 files changed, 27 insertions(+), 8 deletions(-)
 create mode 100644 src/defer.hpp

diff --git a/src/Makefile.am b/src/Makefile.am
index 8d5c5bd..ec1969a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -56,4 +56,5 @@ spice_streaming_agent_SOURCES = \
 	mjpeg-fallback.cpp \
 	jpeg.cpp \
 	jpeg.hpp \
+	defer.hpp \
 	$(NULL)
diff --git a/src/defer.hpp b/src/defer.hpp
new file mode 100644
index 0000000..7fbf9be
--- /dev/null
+++ b/src/defer.hpp
@@ -0,0 +1,16 @@
+// see https://stackoverflow.com/questions/32432450/what-is-standard-defer-finalizer-implementation-in-c
+#ifndef defer
+template <class F> struct deferrer
+{
+    F f;
+    ~deferrer() { f(); }
+};
+struct defer_dummy {};
+template <class F> inline deferrer<F> operator*(defer_dummy, F f)
+{
+    return deferrer<F>{f};
+}
+#define DFRCAT_(LINE) _defer##LINE
+#define DFRCAT(LINE) DFRCAT_(LINE)
+#define defer auto DFRCAT(__LINE__) = defer_dummy{} *[&]() -> void
+#endif
diff --git a/src/spice-streaming-agent.cpp b/src/spice-streaming-agent.cpp
index ed7ddb9..abe746a 100644
--- a/src/spice-streaming-agent.cpp
+++ b/src/spice-streaming-agent.cpp
@@ -33,6 +33,7 @@
 
 #include "hexdump.h"
 #include "concrete-agent.hpp"
+#include "defer.hpp"
 
 using namespace std;
 using namespace SpiceStreamingAgent;
@@ -353,12 +354,19 @@ do_capture(const char *streamport, FILE *f_log)
         // TODO was syslog(LOG_ERR, "Failed to open %s: %s\n", streamport, strerror(errno));
         throw std::runtime_error("failed to open streaming device");
 
+    defer {
+        if (streamfd >= 0) {
+            close(streamfd);
+            streamfd = -1;
+        }
+    };
+
     unsigned int frame_count = 0;
     while (! quit) {
         while (!quit && !streaming_requested) {
             if (read_command(1) < 0) {
                 syslog(LOG_ERR, "FAILED to read command\n");
-                goto done;
+                return;
             }
         }
 
@@ -409,19 +417,13 @@ do_capture(const char *streamport, FILE *f_log)
             //usleep(1);
             if (read_command(0) < 0) {
                 syslog(LOG_ERR, "FAILED to read command\n");
-                goto done;
+                return;
             }
             if (!streaming_requested) {
                 capture->Reset();
             }
         }
     }
-
-done:
-    if (streamfd >= 0) {
-        close(streamfd);
-        streamfd = -1;
-    }
 }
 
 #define arg_error(...) syslog(LOG_ERR, ## __VA_ARGS__);
-- 
2.13.6