Replace assertion with an error message.

(cherry picked from commit 4ec1768415ba015041a9bb28ab17c1ccf6a8c63e)

src/tiffcomposite_int.cpp

@@ -999,9 +999,16 @@ namespace Exiv2 {
         if (!mn_) {
             return TiffEntryBase::doCount();
         }
+#ifndef SUPPRESS_WARNINGS
         // Count of IFD makernote in tag Exif.Photo.MakerNote is the size of the
         // Makernote in bytes
-        assert(tiffType() == ttUndefined || tiffType() == ttUnsignedByte || tiffType() == ttSignedByte);
+        if (tiffType() != ttUndefined && tiffType() != ttUnsignedByte && tiffType() != ttSignedByte) {
+            EXV_ERROR << "Makernote entry 0x" << std::setw(4)
+                      << std::setfill('0') << std::hex << tag()
+                      << " has incorrect Exif (TIFF) type " << std::dec << tiffType()
+                      << ". (Expected signed or unsigned byte.)\n";
+        }
+#endif
         return mn_->size();
     }
 

tests/bugfixes/github/test_issue_1833.py

@@ -0,0 +1,17 @@
+# -*- coding: utf-8 -*-
+
+from system_tests import CaseMeta, path, check_no_ASAN_UBSAN_errors
+
+class TiffMnEntryDoCountInvalidTiffType(metaclass=CaseMeta):
+    """
+    Test for the bug described in:
+    https://github.com/Exiv2/exiv2/issues/1833
+    """
+    url = "https://github.com/Exiv2/exiv2/issues/1833"
+
+    filename = path("$data_path/issue_1833_poc.jpg")
+    commands = ["$exiv2 -pS $filename"]
+    stderr = [""]
+    retval = [0]
+
+    compare_stdout = check_no_ASAN_UBSAN_errors