fix for bad string.c_str() usage on temporary strings (seems to be problematic starting with gcc>=6.3.0, fixes #325 and #326)

src/ebusd/mainloop.cpp

@@ -463,11 +463,12 @@ void MainLoop::notifyDeviceData(symbol_t symbol, bool received) {
     m_logRawLastSymbol = symbol;
   }
   if (symbol == SYN && m_logRawBuffer.tellp() > 0) {  // flush
+    const string bufStr = m_logRawBuffer.str();
+    const char* str = bufStr.c_str();
     if (m_logRawFile) {
-      const char* str = m_logRawBuffer.str().c_str();
       m_logRawFile->write((const unsigned char*)str, strlen(str), received, false);
     } else {
-      logNotice(lf_bus, m_logRawBuffer.str().c_str());
+      logNotice(lf_bus, str);
     }
     m_logRawBuffer.str("");
   }

src/lib/ebus/data.cpp

@@ -775,17 +775,18 @@ result_t ValueListDataField::readSymbols(const SymbolString& input, size_t offse
 result_t ValueListDataField::writeSymbols(size_t offset, istringstream* input,
     SymbolString* output, size_t* usedLength) const {
   const NumberDataType* numType = reinterpret_cast<const NumberDataType*>(m_dataType);
-  if (isIgnored() || input->str() == nullptr_VALUE) {
+  const string inputStr = input->str();
+  if (isIgnored() || inputStr == nullptr_VALUE) {
     // replacement value
     return numType->writeRawValue(numType->getReplacement(), offset, m_length, output, usedLength);
   }
 
-  const char* str = input->str().c_str();
   for (map<unsigned int, string>::const_iterator it = m_values.begin(); it != m_values.end(); ++it) {
-    if (it->second.compare(str) == 0) {
+    if (it->second == inputStr) {
       return numType->writeRawValue(it->first, offset, m_length, output, usedLength);
     }
   }
+  const char* str = inputStr.c_str();
   char* strEnd = nullptr;  // fall back to raw value in input
   unsigned int value;
   value = (unsigned int)strtoul(str, &strEnd, 10);

src/lib/ebus/datatype.cpp

@@ -805,12 +805,13 @@ result_t NumberDataType::writeSymbols(size_t offset, size_t length, istringstrea
     SymbolString* output, size_t* usedLength) const {
   unsigned int value;
 
-  if (!hasFlag(REQ) && (isIgnored() || input->str() == nullptr_VALUE)) {
+  const string inputStr = input->str();
+  if (!hasFlag(REQ) && (isIgnored() || inputStr == nullptr_VALUE)) {
     value = m_replacement;  // replacement value
-  } else if (input->str().empty()) {
+  } else if (inputStr.empty()) {
     return RESULT_ERR_EOF;  // input too short
   } else if (hasFlag(EXP)) {  // IEEE 754 binary32
-    const char* str = input->str().c_str();
+    const char* str = inputStr.c_str();
     char* strEnd = nullptr;
     double dvalue = strtod(str, &strEnd);
     if (strEnd == nullptr || strEnd == str || *strEnd != 0) {
@@ -849,7 +850,7 @@ result_t NumberDataType::writeSymbols(size_t offset, size_t length, istringstrea
     }
 #endif
   } else {
-    const char* str = input->str().c_str();
+    const char* str = inputStr.c_str();
     char* strEnd = nullptr;
     if (m_divisor == 1) {
       if (hasFlag(SIG)) {