use string_views to avoid memory allocations

Source/CPack/WiX/cmWIXAccessControlList.cxx

@@ -2,6 +2,8 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmWIXAccessControlList.h"
 
+#include <cm/string_view>
+
 #include "cmCPackGenerator.h"
 #include "cmStringAlgorithms.h"
 #include "cmSystemTools.h"
@@ -35,12 +37,13 @@ void cmWIXAccessControlList::CreatePermissionElement(std::string const& entry)
     return;
   }
 
-  std::string user_and_domain = entry.substr(0, pos);
-  std::string permission_string = entry.substr(pos + 1);
+  cm::string_view enview(entry);
+  cm::string_view user_and_domain = enview.substr(0, pos);
+  cm::string_view permission_string = enview.substr(pos + 1);
 
   pos = user_and_domain.find('@');
-  std::string user;
-  std::string domain;
+  cm::string_view user;
+  cm::string_view domain;
   if (pos != std::string::npos) {
     user = user_and_domain.substr(0, pos);
     domain = user_and_domain.substr(pos + 1);
@@ -51,9 +54,9 @@ void cmWIXAccessControlList::CreatePermissionElement(std::string const& entry)
   std::vector<std::string> permissions = cmTokenize(permission_string, ",");
 
   this->SourceWriter.BeginElement("Permission");
-  this->SourceWriter.AddAttribute("User", user);
+  this->SourceWriter.AddAttribute("User", std::string(user));
   if (!domain.empty()) {
-    this->SourceWriter.AddAttribute("Domain", domain);
+    this->SourceWriter.AddAttribute("Domain", std::string(domain));
   }
   for (std::string const& permission : permissions) {
     this->EmitBooleanAttribute(entry, cmTrimWhitespace(permission));

Source/CPack/cmCPackNSISGenerator.cxx

@@ -68,7 +68,7 @@ int cmCPackNSISGenerator::PackageFiles()
 
       // Use the custom component install directory if we have one
       if (pos != std::string::npos) {
-        const std::string componentName = fileN.substr(0, pos);
+        auto componentName = cm::string_view(fileN).substr(0, pos);
         outputDir = CustomComponentInstallDirectory(componentName);
       } else {
         outputDir = CustomComponentInstallDirectory(fileN);
@@ -672,7 +672,7 @@ std::string cmCPackNSISGenerator::CreateComponentDescription(
 
   const std::string componentOutputDir =
     CustomComponentInstallDirectory(component->Name);
-  componentCode += "  SetOutPath \"" + componentOutputDir + "\"\n";
+  componentCode += cmStrCat("  SetOutPath \"", componentOutputDir, "\"\n");
 
   // Create the actual installation commands
   if (component->IsDownloaded) {
@@ -921,12 +921,11 @@ std::string cmCPackNSISGenerator::CreateComponentGroupDescription(
 }
 
 std::string cmCPackNSISGenerator::CustomComponentInstallDirectory(
-  const std::string& componentName)
+  cm::string_view componentName)
 {
-  const char* outputDir =
-    this->GetOption("CPACK_NSIS_" + componentName + "_INSTALL_DIRECTORY");
-  const std::string componentOutputDir = (outputDir ? outputDir : "$INSTDIR");
-  return componentOutputDir;
+  const char* outputDir = this->GetOption(
+    cmStrCat("CPACK_NSIS_", componentName, "_INSTALL_DIRECTORY"));
+  return outputDir ? outputDir : "$INSTDIR";
 }
 
 std::string cmCPackNSISGenerator::TranslateNewlines(std::string str)

Source/CPack/cmCPackNSISGenerator.h

@@ -10,6 +10,8 @@
 #include <string>
 #include <vector>
 
+#include <cm/string_view>
+
 #include "cmCPackGenerator.h"
 
 class cmCPackComponent;
@@ -75,8 +77,7 @@ protected:
 
   /// Returns the custom install directory if available for the specified
   /// component, otherwise $INSTDIR is returned.
-  std::string CustomComponentInstallDirectory(
-    const std::string& componentName);
+  std::string CustomComponentInstallDirectory(cm::string_view componentName);
 
   /// Translations any newlines found in the string into \\r\\n, so that the
   /// resulting string can be used within NSIS.

Source/cmAddSubDirectoryCommand.cxx

@@ -4,6 +4,8 @@
 
 #include <cstring>
 
+#include <cm/string_view>
+
 #include "cmExecutionStatus.h"
 #include "cmMakefile.h"
 #include "cmRange.h"
@@ -86,7 +88,8 @@ bool cmAddSubDirectoryCommand(std::vector<std::string> const& args,
     if (binLen > 0 && bin.back() == '/') {
       --binLen;
     }
-    binPath = bin.substr(0, binLen) + srcPath.substr(srcLen);
+    binPath = cmStrCat(cm::string_view(bin).substr(0, binLen),
+                       cm::string_view(srcPath).substr(srcLen));
   } else {
     // Use the binary directory specified.
     // Interpret a relative path with respect to the current binary directory.

Source/cmBinUtilsLinuxELFLinker.cxx

@@ -6,6 +6,7 @@
 #include <sstream>
 
 #include <cm/memory>
+#include <cm/string_view>
 
 #include <cmsys/RegularExpression.hxx>
 
@@ -26,14 +27,16 @@ static std::string ReplaceOrigin(const std::string& rpath,
 
   cmsys::RegularExpressionMatch match;
   if (originRegex.find(rpath.c_str(), match)) {
-    std::string begin = rpath.substr(0, match.start(1));
-    std::string end = rpath.substr(match.end(1));
-    return begin + origin + end;
+    cm::string_view pathv(rpath);
+    auto begin = pathv.substr(0, match.start(1));
+    auto end = pathv.substr(match.end(1));
+    return cmStrCat(begin, origin, end);
   }
   if (originCurlyRegex.find(rpath.c_str(), match)) {
-    std::string begin = rpath.substr(0, match.start());
-    std::string end = rpath.substr(match.end());
-    return begin + origin + end;
+    cm::string_view pathv(rpath);
+    auto begin = pathv.substr(0, match.start());
+    auto end = pathv.substr(match.end());
+    return cmStrCat(begin, origin, end);
   }
   return rpath;
 }

Source/cmCTest.cxx

@@ -17,6 +17,7 @@
 #include <vector>
 
 #include <cm/memory>
+#include <cm/string_view>
 #include <cmext/algorithm>
 
 #include "cmsys/Base64.h"
@@ -2046,13 +2047,15 @@ bool cmCTest::HandleCommandLineArguments(size_t& i,
     return true;
   }
 
-  const std::string noTestsPrefix = "--no-tests=";
+  cm::string_view noTestsPrefix = "--no-tests=";
   if (cmHasPrefix(arg, noTestsPrefix)) {
-    const std::string noTestsMode = arg.substr(noTestsPrefix.length());
+    cm::string_view noTestsMode =
+      cm::string_view(arg).substr(noTestsPrefix.length());
     if (noTestsMode == "error") {
       this->Impl->NoTestsMode = cmCTest::NoTests::Error;
     } else if (noTestsMode != "ignore") {
-      errormsg = "'--no-tests=' given unknown value '" + noTestsMode + "'";
+      errormsg =
+        cmStrCat("'--no-tests=' given unknown value '", noTestsMode, '\'');
       return false;
     } else {
       this->Impl->NoTestsMode = cmCTest::NoTests::Ignore;