diff --git a/.github/workflows/root-ci-config/build_root.py b/.github/workflows/root-ci-config/build_root.py
index bdab8ab2bd254..2a25dae37914b 100755
--- a/.github/workflows/root-ci-config/build_root.py
+++ b/.github/workflows/root-ci-config/build_root.py
@@ -77,7 +77,8 @@ def main():
         # file below overwrites values from above
         **load_config(f'{this_script_dir}/buildconfig/{args.platform}.txt')
     }
-
+    if WINDOWS and pull_request:
+       options_dict["clingtest"] = 'on' if args.clingtest else 'off'
     options = build_utils.cmake_options_from_dict(options_dict)
 
     if WINDOWS:
@@ -197,6 +198,7 @@ def parse_args():
     parser.add_argument("--dockeropts",      default=None,      help="Extra docker options, if any")
     parser.add_argument("--incremental",     default="false",   help="Do incremental build")
     parser.add_argument("--buildtype",       default="Release", help="Release|Debug|RelWithDebInfo")
+    parser.add_argument("--clingtest",       default="false",   help="Build with -Dclingtest=ON for Windows PR CI")
     parser.add_argument("--coverage",        default="false",   help="Create Coverage report in XML")
     parser.add_argument("--sha",             default=None,      help="sha that triggered the event")
     parser.add_argument("--base_ref",        default=None,      help="Ref to target branch")
@@ -212,6 +214,7 @@ def parse_args():
 
     # Set argument to True if matched
     args.incremental = args.incremental.lower() in ('yes', 'true', '1', 'on')
+    args.clingtest = args.clingtest.lower() in ('yes', 'true', '1', 'on')
     args.coverage = args.coverage.lower() in ('yes', 'true', '1', 'on')
     args.binaries = args.binaries.lower() in ('yes', 'true', '1', 'on')
 
diff --git a/.github/workflows/root-ci.yml b/.github/workflows/root-ci.yml
index a1bc5f18aeb4f..2d1434f7d3d7c 100644
--- a/.github/workflows/root-ci.yml
+++ b/.github/workflows/root-ci.yml
@@ -77,7 +77,36 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  git_diff:
+    name: Detect changes in Cling
+    # https://www.meziantou.net/executing-github-actions-jobs-or-steps-only-when-specific-files-change.htm
+    runs-on: ubuntu-latest
+    # Declare output for next jobs
+    outputs:
+      interpreter_changed: ${{ steps.check_file_changed.outputs.interpreter_changed }}
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        # Checkout as many commits as needed for the diff
+        fetch-depth: 2
+    - shell: pwsh
+      id: check_file_changed
+      run: |
+        # Diff HEAD with the latest commit of master
+        $diff = git diff --name-only HEAD^ HEAD
+        # (works with HEAD^ as the last commit fetched is virtual merge commit by GH which shows the full diff for the PR.)
+
+        # Check if a file under interpreter/ has changed
+        $SourceDiff = $diff | Where-Object { $_ -match '^interpreter/' }
+        $HasDiff = $SourceDiff.Length -gt 0
+
+        # Set the output named "interpreter_changed"
+        Write-Host "::set-output name=interpreter_changed::$HasDiff"
+        #echo "interpreter_changed=$HasDiff" >> $GITHUB_OUTPUT
+        echo "interpreter_changed=$HasDiff"
+
   build-macos:
+    needs: [ git_diff ]
     # For any event that is not a PR, the CI will always run. In PRs, the CI
     # can be skipped if the tag [skip-ci] or [skip ci] is written in the title.
     if: |
@@ -95,18 +124,19 @@ jobs:
         # Common configs: {Release,Debug,RelWithDebInfo)
         # Build options: https://root.cern/install/build_from_source/#all-build-options
         include:
-          - platform: mac13   
+          - platform: mac13
             arch: ARM64
             overrides: ["LLVM_ENABLE_ASSERTIONS=On", "builtin_zlib=ON"]
           - platform: mac14
             arch: X64
-            overrides: ["LLVM_ENABLE_ASSERTIONS=On", "CMAKE_CXX_STANDARD=20"]
+            overrides: ["LLVM_ENABLE_ASSERTIONS=On", "CMAKE_CXX_STANDARD=20", "clingtest=${{needs.git_diff.outputs.interpreter_changed == 'true' && 'ON' || 'OFF'}}"]
           - platform: mac15
             arch: ARM64
             overrides: ["LLVM_ENABLE_ASSERTIONS=On", "CMAKE_CXX_STANDARD=20"]
           - platform: mac-beta
             arch: ARM64
             overrides: ["LLVM_ENABLE_ASSERTIONS=On", "CMAKE_CXX_STANDARD=20"]
+            # https://stackoverflow.com/questions/76292948/github-action-boolean-input-with-default-value
 
     runs-on: # Using '[self-hosted, ..., ...]' does not work for some reason :)
       - self-hosted
@@ -115,7 +145,7 @@ jobs:
       - ${{ matrix.platform }}
 
     name: |
-      ${{ matrix.platform }} ${{ matrix.arch }} 
+      ${{ matrix.platform }} ${{ matrix.arch }}
       ${{ (github.event_name != 'schedule' && github.event_name != 'workflow_dispatch' && join( matrix.overrides, ', ' )) || '' }}
 
     steps:
@@ -217,6 +247,7 @@ jobs:
 
 
   build-windows:
+    needs: [ git_diff ]
     # For any event that is not a PR, the CI will always run. In PRs, the CI
     # can be skipped if the tag [skip-ci] or [skip ci] is written in the title.
     if: |
@@ -271,6 +302,7 @@ jobs:
         run: "C:\\setenv.bat ${{ matrix.target_arch }} &&
               python .github/workflows/root-ci-config/build_root.py
                     --buildtype       ${{ matrix.config }}
+                    --clingtest       ${{ needs.git_diff.outputs.interpreter_changed }}
                     --platform        windows10
                     --incremental     $INCREMENTAL
                     --base_ref        ${{ github.base_ref }}
@@ -314,6 +346,7 @@ jobs:
         run: "C:\\setenv.bat ${{ matrix.target_arch }} &&
               python .github/workflows/root-ci-config/build_root.py
                     --buildtype    ${{ matrix.config }}
+                    --clingtest    ${{ needs.git_diff.outputs.interpreter_changed }}
                     --platform     windows10
                     --incremental  false
                     --base_ref     ${{ github.ref_name }}
@@ -338,6 +371,7 @@ jobs:
 
 
   build-linux:
+    needs: [ git_diff ]
     # For any event that is not a PR, the CI will always run. In PRs, the CI
     # can be skipped if the tag [skip-ci] or [skip ci] is written in the title.
     if: |
@@ -350,6 +384,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        # https://github.com/orgs/community/discussions/26253
+        # https://stackoverflow.com/questions/65384420/how-do-i-make-a-github-action-matrix-element-conditional
+        # https://stackoverflow.com/questions/68994484/how-to-skip-a-configuration-of-a-matrix-with-github-actions
+        # https://github.com/joaomcteixeira/python-project-skeleton/pull/31/files        
+
         # Specify image + (optional) build option overrides
         #
         # Available images: https://github.com/root-project/root-ci-images
@@ -363,7 +402,8 @@ jobs:
           - image: alma8
             overrides: ["LLVM_ENABLE_ASSERTIONS=On"]
           - image: alma9
-            overrides: ["LLVM_ENABLE_ASSERTIONS=On", "CMAKE_BUILD_TYPE=Debug"]
+            overrides: ["LLVM_ENABLE_ASSERTIONS=On", "CMAKE_BUILD_TYPE=Debug", "clingtest=${{needs.git_diff.outputs.interpreter_changed == 'true' && 'ON' || 'OFF'}}"]
+            # https://stackoverflow.com/questions/76292948/github-action-boolean-input-with-default-value
           - image: ubuntu22
             overrides: ["imt=Off", "LLVM_ENABLE_ASSERTIONS=On", "CMAKE_BUILD_TYPE=Debug"]
           - image: ubuntu2404
@@ -580,4 +620,4 @@ jobs:
       uses: actions/upload-artifact@v4
       with:
         name: Event File
-        path: ${{ github.event_path }}
+        path: ${{ github.event_path }}
\ No newline at end of file
diff --git a/interpreter/cling/lib/Interpreter/ValueExtractionSynthesizer.cpp b/interpreter/cling/lib/Interpreter/ValueExtractionSynthesizer.cpp
index 41095fc3a9829..f3dde467b87e9 100644
--- a/interpreter/cling/lib/Interpreter/ValueExtractionSynthesizer.cpp
+++ b/interpreter/cling/lib/Interpreter/ValueExtractionSynthesizer.cpp
@@ -22,6 +22,14 @@
 #include "clang/Sema/Sema.h"
 #include "clang/Sema/SemaDiagnostic.h"
 
+// Implements the CValueExtractionPrinter interface.
+extern "C" {
+CLING_LIB_EXPORT
+void cling_SetValueNoAlloc(void* /*cling::Value* V*/) {}
+CLING_LIB_EXPORT
+void cling_SetValueWithAlloc(void* /*cling::Value* V*/) {}
+}
+
 using namespace clang;
 
 namespace cling {
@@ -436,6 +444,10 @@ namespace {
         return VSError(m_Sema, E, "cling::runtime::gCling");
       if (!(NSD = utils::Lookup::Namespace(m_Sema, "internal", NSD)))
         return VSError(m_Sema, E, "cling::runtime::internal namespace");
+    } else {
+      // C, ObjC,...
+      if (!(NSD = utils::Lookup::Namespace(m_Sema, "cling")))
+        return VSError(m_Sema, E, "cling namespace");
     }
     LookupResult R(*m_Sema, &m_Context->Idents.get("setValueNoAlloc"),
                    SourceLocation(), Sema::LookupOrdinaryName,
diff --git a/interpreter/cling/test/Driver/C.c b/interpreter/cling/test/Driver/C.c
index ee302920495b4..05201877e8dd8 100644
--- a/interpreter/cling/test/Driver/C.c
+++ b/interpreter/cling/test/Driver/C.c
@@ -11,13 +11,13 @@
 
 // Validate cling C mode.
 
-// Fix value printing!
-
 int printf(const char*,...);
 printf("CHECK 123 %p\n", gCling); // CHECK: CHECK 123
 
-12 // expected-error {{ValueExtractionSynthesizer could not find: 'cling::runtime::internal::setValueNoAlloc'.}}
-
-32 // expected-error {{ValueExtractionSynthesizer could not find: 'cling::runtime::internal::setValueNoAlloc'.}}
+int i = 1 // CHECK: (int) 1
+sizeof(int) // CHECK: (unsigned long) 4
+int x = sizeof(int);
+printf("CHECK %d\n", x); // CHECK: CHECK 4
 
+// expected-no-diagnostics
 .q