wip! Print hdf5_h_2.java and SYMBOL_LOOKUP debug output when the jextract needle patch fails so macOS CI logs can be used to update needle-macos.txt.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: matteodg

java/CMakeLists.txt

@@ -242,11 +242,49 @@ if (Java_VERSION_STRING VERSION_GREATER_EQUAL "25.0.0")
             endif ()
         endforeach ()
         if (NOT _HDF5_h2_patched)
+            set (_HDF5_HDF5_H_2_LEGACY "${JEXTRACT_OUTPUT_DIR}/org/hdfgroup/javahdf5/hdf5_h_2.java")
+            if (EXISTS "${_HDF5_HDF5_H_2_LEGACY}")
+                file (READ "${_HDF5_HDF5_H_2_LEGACY}" _HDF5_h2_legacy_head LIMIT 8192)
+                string (REPLACE "\r\n" "\n" _HDF5_h2_legacy_head "${_HDF5_h2_legacy_head}")
+                message (
+                    STATUS
+                    "FFM jextract patch debug: beginning of hdf5_h_2.java "
+                    "(use to update needle-macos.txt on macOS if needed):\n"
+                    "${_HDF5_h2_legacy_head}"
+                )
+            else ()
+                message (
+                    STATUS
+                    "FFM jextract patch debug: hdf5_h_2.java not found at "
+                    "${_HDF5_HDF5_H_2_LEGACY}"
+                )
+            endif ()
+            file (READ "${_HDF5_HDF5_H_2}" _HDF5_h2_patch_head LIMIT 8192)
+            string (REPLACE "\r\n" "\n" _HDF5_h2_patch_head "${_HDF5_h2_patch_head}")
+            message (
+                STATUS
+                "FFM jextract patch debug: beginning of patch target "
+                "${_HDF5_HDF5_H_2}:\n${_HDF5_h2_patch_head}"
+            )
+            string (
+                FIND "${_HDF5_h2_src}"
+                "static final SymbolLookup SYMBOL_LOOKUP"
+                _HDF5_h2_lookup_pos
+            )
+            if (NOT _HDF5_h2_lookup_pos EQUAL -1)
+                string (SUBSTRING "${_HDF5_h2_src}" ${_HDF5_h2_lookup_pos} 600 _HDF5_h2_lookup_snippet)
+                message (
+                    STATUS
+                    "FFM jextract patch debug: SYMBOL_LOOKUP block from patch target "
+                    "(exact needle candidate):\n${_HDF5_h2_lookup_snippet}"
+                )
+            endif ()
             message (
                 FATAL_ERROR
                 "Post-jextract patch of ${_HDF5_HDF5_H_2} failed (needle not found). "
                 "jextract output may have changed; update a platform needle under "
-                "${_HDF5_FFM_JEXTRACT_PATCH_DIR}."
+                "${_HDF5_FFM_JEXTRACT_PATCH_DIR}. See STATUS lines above for "
+                "hdf5_h_2.java / SYMBOL_LOOKUP debug output."
             )
         endif ()
         message (STATUS "Patched ${_HDF5_HDF5_H_2} using ${_HDF5_h2_needle_used}")

java/cmake/ffm-jextract-hdf5_h_2/README.txt

@@ -11,5 +11,8 @@ replacement.txt — shared patched block (createHdf5SymbolLookup + helpers).
 CMake picks the first hdf5_h*.java that contains SYMBOL_LOOKUP (jextract may
 place it in hdf5_h_2, hdf5_h_3, etc. depending on declaration split count),
 then tries the host OS needle first and falls back to the other platform needles.
+If the patch fails, CMake prints STATUS debug lines with the beginning of
+hdf5_h_2.java and the SYMBOL_LOOKUP block from the patch target so macOS CI
+logs can be used to update needle-macos.txt.
 If jextract changes its emitted SYMBOL_LOOKUP block, update the matching
 needle-*.txt and keep replacement.txt semantically in sync.