Makefiles: Avoid nested make calls for Fortran module dependencies

Makefiles generated by cmake use a series of nested calls to build
`*.provides.build` targets that are used when the 'requires' step is
needed.  That leads to significant degradation of the build time for
incremental builds.  Re-arrange dependencies to eliminate the nested
calls.

Explicit `.mod.stamp` targets introduced by this commit could lead to
situation when a stamp file always older than its dependency.  This
happens during the incremental build when building of an updated Fortran
source produces a module file that has no differences from the stored
stamp file.  In such case `cmake_copy_f90_mod` will be triggered on each
new build to compare a module file with the corresponding stamp file.
This behavior is expected and can not be changed without nested calls
that slow down the build.  The copy-if-different check is much cheaper
than an entire nested make call.

1 files changed, 1 insertions, 5 deletions

diff --git a/Source/cmMakefileTargetGenerator.cxx b/Source/cmMakefileTargetGenerator.cxx
index 7db010c..ae0b61c 100644
--- a/Source/cmMakefileTargetGenerator.cxx
+++ b/Source/cmMakefileTargetGenerator.cxx
@@ -835,14 +835,10 @@ void cmMakefileTargetGenerator::WriteObjectBuildFile(
   std::string temp = relativeObj;
   temp += ".provides.build";
   std::vector<std::string> r_commands;
-  std::string tgtMakefileName =
-    this->LocalGenerator->GetRelativeTargetDirectory(this->GeneratorTarget);
-  tgtMakefileName += "/build.make";
-  r_commands.push_back(
-    this->LocalGenerator->GetRecursiveMakeCall(tgtMakefileName.c_str(), temp));
 
   p_depends.clear();
   p_depends.push_back(objectRequires);
+  p_depends.push_back(temp);
   this->LocalGenerator->WriteMakeRule(*this->BuildFileStream, nullptr,
                                       objectProvides, p_depends, r_commands,
                                       true);