replace std::string::substr() with operations that do not allocate memory

Modify the original string instead of creating a new copy with substr() when it
is not used for anything else afterwards.

4 files changed, 11 insertions, 5 deletions

diff --git a/Source/CTest/cmCTestGIT.cxx b/Source/CTest/cmCTestGIT.cxx
index 3f3c107..568b091 100644
--- a/Source/CTest/cmCTestGIT.cxx
+++ b/Source/CTest/cmCTestGIT.cxx
@@ -6,6 +6,7 @@
 #include <cstdio>
 #include <cstdlib>
 #include <ctime>
+#include <utility>
 #include <vector>
 
 #include "cmsys/FStream.hxx"
@@ -193,7 +194,8 @@ bool cmCTestGIT::UpdateByFetchAndReset()
       if (line.find("\tnot-for-merge\t") == std::string::npos) {
         std::string::size_type pos = line.find('\t');
         if (pos != std::string::npos) {
-          sha1 = line.substr(0, pos);
+          sha1 = std::move(line);
+          sha1.resize(pos);
         }
       }
     }
diff --git a/Source/CTest/cmCTestScriptHandler.cxx b/Source/CTest/cmCTestScriptHandler.cxx
index 5be9332..4fa4dc0 100644
--- a/Source/CTest/cmCTestScriptHandler.cxx
+++ b/Source/CTest/cmCTestScriptHandler.cxx
@@ -284,12 +284,14 @@ int cmCTestScriptHandler::ReadInScript(const std::string& total_script_arg)
   // if the argument has a , in it then it needs to be broken into the fist
   // argument (which is the script) and the second argument which will be
   // passed into the scripts as S_ARG
-  std::string script = total_script_arg;
+  std::string script;
   std::string script_arg;
   const std::string::size_type comma_pos = total_script_arg.find(',');
   if (comma_pos != std::string::npos) {
     script = total_script_arg.substr(0, comma_pos);
     script_arg = total_script_arg.substr(comma_pos + 1);
+  } else {
+    script = total_script_arg;
   }
   // make sure the file exists
   if (!cmSystemTools::FileExists(script)) {
diff --git a/Source/CTest/cmCTestTestHandler.cxx b/Source/CTest/cmCTestTestHandler.cxx
index c7aef6b..77641c6 100644
--- a/Source/CTest/cmCTestTestHandler.cxx
+++ b/Source/CTest/cmCTestTestHandler.cxx
@@ -1893,7 +1893,8 @@ void cmCTestTestHandler::ExpandTestsToRunInformationForRerunFailed()
         continue;
       }
 
-      int val = atoi(line.substr(0, pos).c_str());
+      line.erase(pos);
+      int val = atoi(line.c_str());
       this->TestsToRun.push_back(val);
     }
     ifs.close();
@@ -2114,7 +2115,7 @@ void cmCTestTestHandler::CleanTestOutput(std::string& output, size_t length)
       ++current;
     }
   }
-  output = output.substr(0, current - begin);
+  output.erase(current - begin);
 
   // Append truncation message.
   std::ostringstream msg;
diff --git a/Source/CTest/cmParseMumpsCoverage.cxx b/Source/CTest/cmParseMumpsCoverage.cxx
index dc1cf30..dc3064d 100644
--- a/Source/CTest/cmParseMumpsCoverage.cxx
+++ b/Source/CTest/cmParseMumpsCoverage.cxx
@@ -113,7 +113,8 @@ bool cmParseMumpsCoverage::LoadPackages(std::string const& d)
   glob.FindFiles(pat);
   for (std::string& file : glob.GetFiles()) {
     std::string name = cmSystemTools::GetFilenameName(file);
-    this->RoutineToDirectory[name.substr(0, name.size() - 2)] = file;
+    name.erase(name.size() - 2);
+    this->RoutineToDirectory[name] = file;
     // initialize each file, this is left out until CDash is fixed
     // to handle large numbers of files
     this->InitializeMumpsFile(file);