(tvm-ffi) branch main updated: [METADATA] Always return metadata string as created in main lib (#305)

[tqchen]

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tqchen pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/tvm-ffi.git


The following commit(s) were added to refs/heads/main by this push:
     new dcacb98  [METADATA] Always return metadata string as created in main 
lib (#305)
dcacb98 is described below

commit dcacb98d189241d52ef51c1d63fb0e9f6c98a4b0
Author: Tianqi Chen <tqc...@users.noreply.github.com>
AuthorDate: Tue Dec 2 17:07:53 2025 -0500

    [METADATA] Always return metadata string as created in main lib (#305)
    
    This PR updates the metadata string creation as always allocating from
    the libtvm_ffi so to avoid possible delete after module unloading issue.
---
 include/tvm/ffi/function.h | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/include/tvm/ffi/function.h b/include/tvm/ffi/function.h
index 3f6fe9b..f2cd61f 100644
--- a/include/tvm/ffi/function.h
+++ b/include/tvm/ffi/function.h
@@ -922,6 +922,8 @@ inline int32_t TypeKeyToIndex(std::string_view type_key) {
  * TVM_FFI_DLL_EXPORT_INCLUDE_METADATA is defined)
  */
 #if TVM_FFI_DLL_EXPORT_INCLUDE_METADATA
+// Implementation note: we specifically use TVMFFIStringFromByteArray
+// so the returned string metadata is allocated in the libtvm_ffi and long 
lived.
 #define TVM_FFI_DLL_EXPORT_TYPED_FUNC(ExportName, Function)                    
                  \
   TVM_FFI_DLL_EXPORT_TYPED_FUNC_IMPL_(ExportName, Function)                    
                  \
   extern "C" {                                                                 
                  \
@@ -932,8 +934,9 @@ inline int32_t TypeKeyToIndex(std::string_view type_key) {
     std::ostringstream os;                                                     
                  \
     os << R"({"type_schema":)"                                                 
                  \
        << ::tvm::ffi::EscapeString(::tvm::ffi::String(FuncInfo::TypeSchema())) 
<< R"(})";        \
-    ::tvm::ffi::String str(os.str());                                          
                  \
-    ::tvm::ffi::TypeTraits<::tvm::ffi::String>::MoveToAny(std::move(str), 
result);               \
+    std::string data = os.str();                                               
                  \
+    TVMFFIByteArray data_array{data.data(), data.size()};                      
                  \
+    return TVMFFIStringFromByteArray(&data_array, result);                     
                  \
     TVM_FFI_SAFE_CALL_END();                                                   
                  \
   }                                                                            
                  \
   }
@@ -983,13 +986,16 @@ inline int32_t TypeKeyToIndex(std::string_view type_key) {
  *       This symbol is only exported when TVM_FFI_DLL_EXPORT_INCLUDE_METADATA 
is defined.
  */
 #if TVM_FFI_DLL_EXPORT_INCLUDE_METADATA
+// Implementation note: we specifically use TVMFFIStringFromByteArray
+// so the returned string metadata is allocated in the libtvm_ffi and long 
lived.
 #define TVM_FFI_DLL_EXPORT_TYPED_FUNC_DOC(ExportName, DocString)               
             \
   extern "C" {                                                                 
             \
   TVM_FFI_DLL_EXPORT int __tvm_ffi__doc_##ExportName(void* self, const 
TVMFFIAny* args,     \
                                                      int32_t num_args, 
TVMFFIAny* result) { \
     TVM_FFI_SAFE_CALL_BEGIN();                                                 
             \
-    ::tvm::ffi::String str(DocString);                                         
             \
-    ::tvm::ffi::TypeTraits<::tvm::ffi::String>::MoveToAny(std::move(str), 
result);          \
+    std::string_view data(DocString);                                          
             \
+    TVMFFIByteArray data_array{data.data(), data.size()};                      
             \
+    return TVMFFIStringFromByteArray(&data_array, result);                     
             \
     TVM_FFI_SAFE_CALL_END();                                                   
             \
   }                                                                            
             \
   }