Fix exception safety in subprocess

src/cpp-utils/process/subprocess.cpp

@@ -26,44 +26,54 @@ constexpr const char* openmode = "r";
 using std::string;
 
 namespace cpputils {
-    //TODO Exception safety
-
     namespace {
-    FILE *_call(const string &command) {
+	class SubprocessHandle final {
-        FILE *subprocess = popen(command.c_str(), openmode);
+	public:
-        if (!subprocess)
+		SubprocessHandle(const string &command)
-        {
+		: _subprocess(popen(command.c_str(), openmode)) {
-            throw std::runtime_error("Error starting subprocess "+command + ". Errno: " + std::to_string(errno));
+			if (!_subprocess) {
-        }
+				throw std::runtime_error("Error starting subprocess " + command + ". Errno: " + std::to_string(errno));
-        return subprocess;
+			}
-    }
+		}
 
-    string _getOutput(FILE *subprocess) {
+		~SubprocessHandle() {
-        string output;
+			if (_subprocess != nullptr) {
-        char buffer[1024];
+				close();
-        while(fgets(buffer, sizeof(buffer), subprocess) != nullptr) {
+			}
-            output += buffer;
+		}
-        }
+
-        return output;
+		string getOutput() {
-    }
+			string output;
+			char buffer[1024];
+			while (fgets(buffer, sizeof(buffer), _subprocess) != nullptr) {
+				output += buffer;
+			}
+			return output;
+		}
+
+		int close() {
+			auto returncode = pclose(_subprocess);
+			_subprocess = nullptr;
+			if (returncode == -1) {
+				throw std::runtime_error("Error calling pclose. Errno: " + std::to_string(errno));
+			}
+			if (!WIFEXITED(returncode)) {
+				// WEXITSTATUS is only valid if WIFEXITED is 0.
+				throw std::runtime_error("WIFEXITED returned " + std::to_string(WIFEXITED(returncode)));
+			}
+			return WEXITSTATUS(returncode);
+		}
+
+	private:
+		FILE *_subprocess;
+	};
 
-    int _close(FILE *subprocess) {
-        auto returncode = pclose(subprocess);
-        if(returncode == -1) {
-            throw std::runtime_error("Error calling pclose. Errno: " + std::to_string(errno));
-        }
-        if (!WIFEXITED(returncode)) {
-            // WEXITSTATUS is only valid if WIFEXITED is 0.
-            throw std::runtime_error("WIFEXITED returned " + std::to_string(WIFEXITED(returncode)));
-        }
-        return WEXITSTATUS(returncode);
-    }
     }
 
     SubprocessResult Subprocess::call(const string &command) {
-        FILE *subprocess = _call(command);
+		SubprocessHandle subprocess(command);
-        string output = _getOutput(subprocess);
+        string output = subprocess.getOutput();
-        int exitcode = _close(subprocess);
+        int exitcode = subprocess.close();
 
         return SubprocessResult {output, exitcode};
     }