[CMake] [PATCH] Optionally skip link dependencies on shared library files

[Brad King]

Add target property LINK_DEPENDS_NO_SHARED and initialization variable
CMAKE_LINK_DEPENDS_NO_SHARED to enable this behavior.

Suggested-by: Leif Walsh <leif.walsh at gmail.com>
---

On 08/03/2012 04:57 PM, Leif Walsh wrote:
> On 3 Aug, 2012, at 4:44 PM, Andreas Pakulat <apaku at gmx.de> wrote:
>> Actually no, adding new public API, changing existing API in
>> compatible ways are things you can do with a shared library which
>> needs relinking.
> 
> Not without changing the header files, which forces
> recompilation.  As the author of a shared library, your header
> files are your contract with your clients.

Great point.  Please try this patch on top of 2.8.10-rc3.
Then build with -DCMAKE_LINK_DEPENDS_NO_SHARED=1 or add

 set(CMAKE_LINK_DEPENDS_NO_SHARED 1)

to the top of your project.

-Brad

 Source/cmComputeLinkInformation.cxx |   10 +++++++++-
 Source/cmComputeLinkInformation.h   |    1 +
 Source/cmDocumentVariables.cxx      |    9 +++++++++
 Source/cmTarget.cxx                 |   17 +++++++++++++++++
 4 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/Source/cmComputeLinkInformation.cxx b/Source/cmComputeLinkInformation.cxx
index cd3ef59..d8ffb5e 100644
--- a/Source/cmComputeLinkInformation.cxx
+++ b/Source/cmComputeLinkInformation.cxx
@@ -277,6 +277,10 @@ cmComputeLinkInformation
   this->UseImportLibrary =
     this->Makefile->GetDefinition("CMAKE_IMPORT_LIBRARY_SUFFIX")?true:false;
 
+  // Check whether we should skip dependencies on shared library files.
+  this->LinkDependsNoShared =
+    this->Target->GetPropertyAsBool("LINK_DEPENDS_NO_SHARED");
+
   // On platforms without import libraries there may be a special flag
   // to use when creating a plugin (module) that obtains symbols from
   // the program that will load it.
@@ -650,7 +654,11 @@ void cmComputeLinkInformation::AddItem(std::string const& item, cmTarget* tgt)
 
       // Pass the full path to the target file.
       std::string lib = tgt->GetFullPath(config, implib, true);
-      this->Depends.push_back(lib);
+      if(!this->LinkDependsNoShared ||
+         tgt->GetType() != cmTarget::SHARED_LIBRARY)
+        {
+        this->Depends.push_back(lib);
+        }
 
       this->AddTargetItem(lib, tgt);
       this->AddLibraryRuntimeInfo(lib, tgt);
diff --git a/Source/cmComputeLinkInformation.h b/Source/cmComputeLinkInformation.h
index f60f8d3..e0078af 100644
--- a/Source/cmComputeLinkInformation.h
+++ b/Source/cmComputeLinkInformation.h
@@ -82,6 +82,7 @@ private:
   // Configuration information.
   const char* Config;
   const char* LinkLanguage;
+  bool LinkDependsNoShared;
 
   // Modes for dealing with dependent shared libraries.
   enum SharedDepMode
diff --git a/Source/cmDocumentVariables.cxx b/Source/cmDocumentVariables.cxx
index 8db0e8f..55d70f8 100644
--- a/Source/cmDocumentVariables.cxx
+++ b/Source/cmDocumentVariables.cxx
@@ -1222,6 +1222,15 @@ void cmDocumentVariables::DefineVariables(cmake* cm)
      "Variables that Control the Build");
 
   cm->DefineProperty
+    ("CMAKE_LINK_DEPENDS_NO_SHARED", cmProperty::VARIABLE,
+     "Whether to skip link dependencies on shared library files.",
+     "This variable initializes the LINK_DEPENDS_NO_SHARED "
+     "property on targets when they are created.  "
+     "See that target property for additional information.",
+     false,
+     "Variables that Control the Build");
+
+  cm->DefineProperty
     ("CMAKE_AUTOMOC", cmProperty::VARIABLE,
      "Whether to handle moc automatically for Qt targets.",
      "This variable is used to initialize the "
diff --git a/Source/cmTarget.cxx b/Source/cmTarget.cxx
index 423b350..9cfcb63 100644
--- a/Source/cmTarget.cxx
+++ b/Source/cmTarget.cxx
@@ -651,6 +651,22 @@ void cmTarget::DefineProperties(cmake *cm)
      "custom Makefile link rules.");
 
   cm->DefineProperty
+    ("LINK_DEPENDS_NO_SHARED", cmProperty::TARGET,
+     "Do not depend on linked shared library files.",
+     "Set this property to true to tell CMake generators not to add "
+     "file-level dependencies on the shared library files linked by "
+     "this target.  "
+     "Modification to the shared libraries will not be sufficient to "
+     "re-link this target.  "
+     "Logical target-level dependencies will not be affected so the "
+     "linked shared libraries will still be brought up to date before "
+     "this target is built."
+     "\n"
+     "This property is initialized by the value of the variable "
+     "CMAKE_LINK_DEPENDS_NO_SHARED if it is set when a target is "
+     "created.");
+
+  cm->DefineProperty
     ("LINK_INTERFACE_LIBRARIES", cmProperty::TARGET,
      "List public interface libraries for a shared library or executable.",
      "By default linking to a shared library target transitively "
@@ -1314,6 +1330,7 @@ void cmTarget::SetMakefile(cmMakefile* mf)
   this->SetPropertyDefault("OSX_ARCHITECTURES", 0);
   this->SetPropertyDefault("AUTOMOC", 0);
   this->SetPropertyDefault("AUTOMOC_MOC_OPTIONS", 0);
+  this->SetPropertyDefault("LINK_DEPENDS_NO_SHARED", 0);
   this->SetPropertyDefault("LINK_INTERFACE_LIBRARIES", 0);
   this->SetPropertyDefault("WIN32_EXECUTABLE", 0);
   this->SetPropertyDefault("MACOSX_BUNDLE", 0);
-- 
1.7.10.4