Fixed the build (#449)

Some linux releases have turned on _FORTIFY_SOURCE=2, which broke our build. This PR tries to fix it

src/common/base/Configuration.cpp

@@ -42,7 +42,8 @@ Status Configuration::parseFromFile(const std::string &filename) {
         // read the whole content
         // TODO(dutor) ::read might be interrupted by signals
         auto buffer = std::make_unique<char[]>(len + 1);
-        ::read(fd, buffer.get(), len);
+        auto charsRead = ::read(fd, buffer.get(), len);
+        UNUSED(charsRead);
         buffer[len] = '\0';
         // strip off all comments
         static const std::regex comment("//.*|#.*");

src/common/network/NetworkUtils.cpp

@@ -91,7 +91,16 @@ bool NetworkUtils::getDynamicPortRange(uint16_t& low, uint16_t& high) {
         return false;
     }
 
-    fscanf(pipe, "%hu %hu", &low, &high);
+    if (fscanf(pipe, "%hu %hu", &low, &high) != 2) {
+        LOG(ERROR) << "Failed to read from /proc/sys/net/ipv4/ip_local_port_range";
+        // According to ICANN, the port range is devided into three sections
+        //
+        // Well-known ports: 0 to 1023 (used for system services)
+        // Registered/user ports: 1024 to 49151
+        // Dynamic/private ports: 49152 to 65535
+        low = 49152;
+        high = 65535;
+    }
 
     if (pclose(pipe) < 0) {
         LOG(ERROR) << "Failed to close the pipe: " << strerror(errno);

src/common/network/test/NetworkUtilsTest.cpp

@@ -16,7 +16,8 @@ TEST(NetworkUtils, getHostname) {
 
     FILE* fp = popen("LD_PRELOAD= hostname | tr -d ['\n']", "r");
     char buffer[256];
-    fgets(buffer, sizeof(buffer), fp);
+    auto numChars = fgets(buffer, sizeof(buffer), fp);
+    UNUSED(numChars);
     pclose(fp);
     EXPECT_EQ(std::string(buffer), hostname);
 }

src/common/process/test/ProcessTest.cpp

@@ -23,7 +23,8 @@ TEST(ProcessUtils, getExeCWD) {
     auto result = ProcessUtils::getExeCWD();
     ASSERT_TRUE(result.ok()) << result.status();
     char buffer[PATH_MAX];
-    ::getcwd(buffer, sizeof(buffer));
+    auto len = ::getcwd(buffer, sizeof(buffer));
+    UNUSED(len);
     ASSERT_EQ(buffer, result.value());
 }