Use const reference parameters for efficiency to not make copies

Flagged by Coverity Scan.

Author: eldering

judge/runpipe.cc

@@ -912,7 +912,7 @@ int main(int argc, char **argv) {
   }
 
   // The exit status should match the one of the first command.
-  auto main_process = state.main_process();
+  auto &main_process = state.main_process();
   int exit_code = main_process.exit_code();
   if (exit_code != -1) {
     return exit_code;

sql/files/defaultdata/compare/compare.cc

@@ -90,7 +90,7 @@ bool equal_case_insensitive(std::string a, std::string b)
 /* Test two floating-point numbers for equality, accounting for +/-INF, NaN, and precision.
  * Float `jval` is considered the reference value for relative error.
  */
-void compare_float(std::string judge, std::string team, flt jval, flt tval, flt float_abs_tol, flt float_rel_tol, std::string extra_msg) {
+void compare_float(const std::string &judge, const std::string &team, flt jval, flt tval, flt float_abs_tol, flt float_rel_tol, const std::string &extra_msg) {
 	/* Finite values are compared with some tolerance */
 	if (std::isfinite(tval) && std::isfinite(jval)) {
 		flt absdiff = fabsl(tval-jval);