file: Change REMOVE to ignore empty names

Previously code like

    file(REMOVE_RECURSE "${accidentally_missing_variable}")

treated the empty string as a relative path with respect to the
current directory and removed its contents.  Change this behavior
to ignore the empty string with a warning instead.

Normally such behavior changes are done with a policy, but in this case
such code is likely a real bug in project code that can delete data.

Fixes: #19274

1 files changed, 6 insertions, 0 deletions

diff --git a/Source/cmFileCommand.cxx b/Source/cmFileCommand.cxx
index f5ec9fe..1349910 100644
--- a/Source/cmFileCommand.cxx
+++ b/Source/cmFileCommand.cxx
@@ -1405,6 +1405,12 @@ bool cmFileCommand::HandleRemove(std::vector<std::string> const& args,
        cmMakeRange(args).advance(1)) // Get rid of subcommand
   {
     std::string fileName = arg;
+    if (fileName.empty()) {
+      std::string const r = recurse ? "REMOVE_RECURSE" : "REMOVE";
+      this->Makefile->IssueMessage(MessageType::AUTHOR_WARNING,
+                                   "Ignoring empty file name in " + r + ".");
+      continue;
+    }
     if (!cmsys::SystemTools::FileIsFullPath(fileName)) {
       fileName = this->Makefile->GetCurrentSourceDirectory();
       fileName += "/" + arg;