1 files changed, 12 insertions, 8 deletions
diff --git a/libbutl/diagnostics.hxx b/libbutl/diagnostics.hxx
index 23aa14f..c6db34b 100644
--- a/libbutl/diagnostics.hxx
+++ b/libbutl/diagnostics.hxx
@@ -27,8 +27,11 @@ namespace butl
   LIBBUTL_SYMEXPORT extern std::ostream* diag_stream;
 
   // Acquire the diagnostics exclusive access mutex in ctor, release in dtor.
-  // An object of the type must be created prior to writing to diag_stream (see
-  // above).
+  // An object of the type must be created prior to writing to diag_stream
+  // (see above).
+  //
+  // Note that this class also manages the interaction with the progress
+  // printing (see below).
   //
   struct LIBBUTL_SYMEXPORT diag_stream_lock
   {
@@ -92,7 +95,8 @@ namespace butl
   template <typename> struct diag_prologue;
   template <typename> struct diag_mark;
 
-  using diag_epilogue = void (const diag_record&);
+  using diag_writer = void (const diag_record&);
+  using diag_epilogue = void (const diag_record&, diag_writer*);
 
   struct LIBBUTL_SYMEXPORT diag_record
   {
@@ -129,7 +133,7 @@ namespace butl
     full () const {return !empty_;}
 
     void
-    flush () const;
+    flush (diag_writer* = nullptr) const;
 
     void
     append (const char* indent, diag_epilogue* e) const
@@ -162,7 +166,7 @@ namespace butl
 #endif
         empty_ (r.empty_),
         epilogue_ (r.epilogue_),
-        os (std::move (r.os))
+        os (std::move (r.os)) // Note: can throw.
     {
       if (!empty_)
       {
@@ -180,7 +184,7 @@ namespace butl
     // Diagnostics writer. The default implementation writes the record text
     // to diag_stream. If it is NULL, then the record text is ignored.
     //
-    static void (*writer) (const diag_record&);
+    static diag_writer* writer;
 
   protected:
 #ifdef __cpp_lib_uncaught_exceptions
@@ -315,10 +319,10 @@ namespace butl
         stack (prev_);
     }
 
-    // Normally passed as an epilogue.
+    // Normally passed as an epilogue. Writer is not used.
     //
     static void
-    apply (const diag_record& r)
+    apply (const diag_record& r, diag_writer* = nullptr)
     {
       for (const diag_frame* f (stack ()); f != nullptr; f = f->prev_)
         f->func_ (*f, r);