cmake: Enable --warn-uninitialized inside string(CONFIGURE) and configure_file

Fixes: #18489

3 files changed, 19 insertions, 12 deletions

diff --git a/Source/cmCommandArgumentParserHelper.cxx b/Source/cmCommandArgumentParserHelper.cxx
index f94dc24..ca29967 100644
--- a/Source/cmCommandArgumentParserHelper.cxx
+++ b/Source/cmCommandArgumentParserHelper.cxx
@@ -92,9 +92,11 @@ const char* cmCommandArgumentParserHelper::ExpandVariable(const char* var)
     return this->AddString(ostr.str());
   }
   const char* value = this->Makefile->GetDefinition(var);
-  if (!value && !this->RemoveEmpty) {
+  if (!value) {
     this->Makefile->MaybeWarnUninitialized(var, this->FileName);
-    return nullptr;
+    if (!this->RemoveEmpty) {
+      return nullptr;
+    }
   }
   if (this->EscapeQuotes && value) {
     return this->AddString(cmSystemTools::EscapeQuotes(value));
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 256202c..68a5101 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -2522,9 +2522,9 @@ const std::string& cmMakefile::ExpandVariablesInString(
       // Suppress variable watches to avoid calling hooks twice. Suppress new
       // dereferences since the OLD behavior is still what is actually used.
       this->SuppressSideEffects = true;
-      newError = ExpandVariablesInStringNew(
-        newErrorstr, newResult, escapeQuotes, noEscapes, atOnly, filename,
-        line, removeEmpty, replaceAt);
+      newError = ExpandVariablesInStringNew(newErrorstr, newResult,
+                                            escapeQuotes, noEscapes, atOnly,
+                                            filename, line, replaceAt);
       this->SuppressSideEffects = false;
       CM_FALLTHROUGH;
     }
@@ -2537,9 +2537,9 @@ const std::string& cmMakefile::ExpandVariablesInString(
     case cmPolicies::REQUIRED_ALWAYS:
     // Messaging here would be *very* verbose.
     case cmPolicies::NEW:
-      mtype = ExpandVariablesInStringNew(errorstr, source, escapeQuotes,
-                                         noEscapes, atOnly, filename, line,
-                                         removeEmpty, replaceAt);
+      mtype =
+        ExpandVariablesInStringNew(errorstr, source, escapeQuotes, noEscapes,
+                                   atOnly, filename, line, replaceAt);
       break;
   }
 
@@ -2726,7 +2726,7 @@ bool cmMakefile::IsProjectFile(const char* filename) const
 cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
   std::string& errorstr, std::string& source, bool escapeQuotes,
   bool noEscapes, bool atOnly, const char* filename, long line,
-  bool removeEmpty, bool replaceAt) const
+  bool replaceAt) const
 {
   // This method replaces ${VAR} and @VAR@ where VAR is looked up
   // with GetDefinition(), if not found in the map, nothing is expanded.
@@ -2783,7 +2783,7 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
             } else {
               varresult = value;
             }
-          } else if (!removeEmpty && !this->SuppressSideEffects) {
+          } else if (!this->SuppressSideEffects) {
             this->MaybeWarnUninitialized(lookup, filename);
           }
           result.replace(var.loc, result.size() - var.loc, varresult);
@@ -2896,7 +2896,12 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
             if (filename && variable == lineVar) {
               varresult = std::to_string(line);
             } else {
-              varresult = this->GetSafeDefinition(variable);
+              const std::string* def = this->GetDef(variable);
+              if (def) {
+                varresult = *def;
+              } else if (!this->SuppressSideEffects) {
+                this->MaybeWarnUninitialized(variable, filename);
+              }
             }
 
             if (escapeQuotes) {
diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index 1a2a0e7..1607735 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -990,7 +990,7 @@ private:
   cmake::MessageType ExpandVariablesInStringNew(
     std::string& errorstr, std::string& source, bool escapeQuotes,
     bool noEscapes, bool atOnly, const char* filename, long line,
-    bool removeEmpty, bool replaceAt) const;
+    bool replaceAt) const;
   /**
    * Old version of GetSourceFileWithOutput(const std::string&) kept for
    * backward-compatibility. It implements a linear search and support