cmMakefile: Let AddDefinition accept a value as cm::string_view

This changes `cmMakefile::AddDefinition` to take a `cm::string_view` as value
argument instead of a `const char *`.

Benefits are:
- `std::string` can be passed to `cmMakefile::AddDefinition` directly without
  the `c_str()` plus string length recomputation fallback.
- Lengths of literals passed to `cmMakefile::AddDefinition` can be computed at
  compile time.

In various sources uses of `cmMakefile::AddDefinition` are adapted to avoid
`std::string::c_str` calls and the `std::string` is passed directly.
Uses of `cmMakefile::AddDefinition`, where a `nullptr` `const char*` might
be passed to `cmMakefile::AddDefinition` are extended with `nullptr` checks.

1 files changed, 4 insertions, 4 deletions

diff --git a/Source/cmForEachCommand.cxx b/Source/cmForEachCommand.cxx
index e3918b5..06dce2c 100644
--- a/Source/cmForEachCommand.cxx
+++ b/Source/cmForEachCommand.cxx
@@ -53,7 +53,7 @@ bool cmForEachFunctionBlocker::IsFunctionBlocked(const cmListFileFunction& lff,
 
       for (std::string const& arg : cmMakeRange(this->Args).advance(1)) {
         // set the variable to the loop value
-        mf.AddDefinition(this->Args[0], arg.c_str());
+        mf.AddDefinition(this->Args[0], arg);
         // Invoke all the functions that were collected in the block.
         cmExecutionStatus status(mf);
         for (cmListFileFunction const& func : this->Functions) {
@@ -62,12 +62,12 @@ bool cmForEachFunctionBlocker::IsFunctionBlocked(const cmListFileFunction& lff,
           if (status.GetReturnInvoked()) {
             inStatus.SetReturnInvoked();
             // restore the variable to its prior value
-            mf.AddDefinition(this->Args[0], oldDef.c_str());
+            mf.AddDefinition(this->Args[0], oldDef);
             return true;
           }
           if (status.GetBreakInvoked()) {
             // restore the variable to its prior value
-            mf.AddDefinition(this->Args[0], oldDef.c_str());
+            mf.AddDefinition(this->Args[0], oldDef);
             return true;
           }
           if (status.GetContinueInvoked()) {
@@ -80,7 +80,7 @@ bool cmForEachFunctionBlocker::IsFunctionBlocked(const cmListFileFunction& lff,
       }
 
       // restore the variable to its prior value
-      mf.AddDefinition(this->Args[0], oldDef.c_str());
+      mf.AddDefinition(this->Args[0], oldDef);
       return true;
     }
     // close out a nested foreach