Makefiles: provide, but do not consume, "forward linked" target dirs

Makefiles do not have a per-object sense of where they come from, so
forwarding any module information here would end up with incorrect
module file path construction by consuming targets. Leave a TODO item in
its place.

2 files changed, 17 insertions, 0 deletions

diff --git a/Source/cmDependsFortran.cxx b/Source/cmDependsFortran.cxx
index 2a50565..b23dabd 100644
--- a/Source/cmDependsFortran.cxx
+++ b/Source/cmDependsFortran.cxx
@@ -258,6 +258,12 @@ bool cmDependsFortran::LocateModules()
     }
     this->MatchRemoteModules(fin, targetDir);
   }
+
+  // TODO: Use `CMAKE_Fortran_TARGET_FORWARD_LINKED_INFO_FILES` to handle cases
+  // described in #25425. Note that because Makefiles generators do not
+  // implement relaxed object compilation as described in #15555, the issues
+  // never actually cause build failures; only incremental build incorrectness.
+
   return true;
 }
 
diff --git a/Source/cmMakefileTargetGenerator.cxx b/Source/cmMakefileTargetGenerator.cxx
index 3ad0928..74b4b75 100644
--- a/Source/cmMakefileTargetGenerator.cxx
+++ b/Source/cmMakefileTargetGenerator.cxx
@@ -1446,6 +1446,17 @@ void cmMakefileTargetGenerator::WriteTargetDependRules()
       *this->InfoFileStream << "  \"" << d << "/DependInfo.cmake\"\n";
     }
     *this->InfoFileStream << "  )\n";
+
+    /* clang-format off */
+  *this->InfoFileStream
+    << "\n"
+       "# Targets to which this target links which contain Fortran sources.\n"
+       "set(CMAKE_Fortran_TARGET_FORWARD_LINKED_INFO_FILES\n";
+    /* clang-format on */
+    for (std::string const& d : dirs.Forward) {
+      *this->InfoFileStream << "  \"" << d << "/DependInfo.cmake\"\n";
+    }
+    *this->InfoFileStream << "  )\n";
   }
 
   std::string const& working_dir =