SysFS: switch to boost::regex to stay compatible with GCC versions < 4.9

Makefile

@@ -76,7 +76,7 @@ src/sensors/%.o: CXXFLAGS+= $(PLUGINFLAGS) -I$(DCDBDEPSPATH)/bacnet-stack-$(BACN
 #src/sensors/*/%.o: %.cpp
 
 libdcdbplugin_sysfs.$(LIBEXT): src/sensors/sysfs/SysfsSensorGroup.o src/sensors/sysfs/SysfsConfigurator.o
-	$(CXX) $(LIBFLAGS)$@ -o $@ $^ -L$(DCDBDEPLOYPATH)/lib/ -lboost_log -lboost_system
+	$(CXX) $(LIBFLAGS)$@ -o $@ $^ -L$(DCDBDEPLOYPATH)/lib/ -lboost_log -lboost_system -lboost_regex
 
 libdcdbplugin_perfevent.$(LIBEXT): src/sensors/perfevent/PerfSensorGroup.o src/sensors/perfevent/PerfeventConfigurator.o
 	$(CXX) $(LIBFLAGS)$@ -o $@ $^ -L$(DCDBDEPLOYPATH)/lib/ -lboost_log -lboost_system

src/sensors/sysfs/SysfsSensorBase.h

@@ -10,7 +10,7 @@
 
 #include "../../includes/SensorBase.h"
 
-#include <regex>
+#include <boost/regex.hpp>
 
 class SysfsSensorBase : public SensorBase {
 public:
@@ -24,7 +24,7 @@ public:
 	virtual ~SysfsSensorBase() {}
 
 	bool 				hasFilter()	const { return _filter; }
-	std::regex			getRegex()	const { return _regx;	}
+	boost::regex		getRegex()	const { return _regx;	}
 	const std::string&	getSubstitution()	const { return _substitution; }
 
 	void setFilter(bool filter)				{ _filter = filter; }
@@ -32,25 +32,25 @@ public:
 		setFilter(true);
 
 		//check if input has sed format of "s/.../.../" for substitution
-		std::regex checkSubstitute("s([^\\\\]{1})([\\S|\\s]*)\\1([\\S|\\s]*)\\1");
-		std::smatch matchResults;
+		boost::regex checkSubstitute("s([^\\\\]{1})([\\S|\\s]*)\\1([\\S|\\s]*)\\1");
+		boost::smatch matchResults;
 
 		if(regex_match(filter, matchResults, checkSubstitute)) {
 			//input has substitute format
-			setRegex(std::regex(matchResults[2].str(), std::regex_constants::extended));
+			setRegex(boost::regex(matchResults[2].str(), boost::regex_constants::extended));
 			setSubstitution(matchResults[3].str());
 		} else {
 			//input is only a regex
-			setRegex(std::regex(filter, std::regex_constants::extended));
+			setRegex(boost::regex(filter, boost::regex_constants::extended));
 			setSubstitution("&");
 		}
 	}
-	void setRegex(std::regex regx)			{ _regx = regx; }
+	void setRegex(boost::regex regx)			{ _regx = regx; }
 	void setSubstitution(const std::string& substitution)	{ _substitution = substitution; }
 
 protected:
 	bool _filter;
-	std::regex _regx;
+	boost::regex _regx;
 	std::string _substitution;
 };
 

src/sensors/sysfs/SysfsSensorGroup.cpp

@@ -7,6 +7,7 @@
 
 #include "timestamp.h"
 #include <functional>
+#include <cstring>
 #include "SysfsSensorGroup.h"
 
 using namespace std;
@@ -70,7 +71,13 @@ void SysfsSensorGroup::read() {
 					//substitution must have sed format
 					//if no substitution is defined the whole regex-match is copied as is.
 					//parts which do not match are not copied --> filter
-					reading.value = stoll(regex_replace(buf, s->getRegex(), s->getSubstitution(), regex_constants::format_sed | regex_constants::format_no_copy));
+
+					//reading.value = stoll(regex_replace(buf, s->getRegex(), s->getSubstitution(), boost::regex_constants::format_sed | boost::regex_constants::format_no_copy));
+					//there is no 1:1 match for the std::regex_replace function used previously, but the code below should have the same outcome
+					std::string input(buf);
+					std::string result;
+					boost::regex_replace(std::back_inserter(result), input.begin(), input.end(), s->getRegex(), s->getSubstitution().c_str(), boost::regex_constants::format_sed | boost::regex_constants::format_no_copy);
+					reading.value = stoll(result);
 				} else {
 					reading.value = stoll(buf);
 				}