fix(mbyte): check for utf8proc_map() failure (#30531)

2 files changed, 13 insertions, 3 deletions

diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index e1701bb931..05f81c48a9 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -1380,11 +1380,15 @@ int utf_fold(int a)
   }
 
   utf8proc_uint8_t input_str[16] = { 0 };
-  utf8proc_encode_char(a, input_str);
+  if (utf8proc_encode_char(a, input_str) <= 0) {
+    return a;
+  }
 
   utf8proc_uint8_t *fold_str_utf;
-  utf8proc_map((utf8proc_uint8_t *)input_str, 0, &fold_str_utf,
-               UTF8PROC_NULLTERM | UTF8PROC_CASEFOLD);
+  if (utf8proc_map((utf8proc_uint8_t *)input_str, 0, &fold_str_utf,
+                   UTF8PROC_NULLTERM | UTF8PROC_CASEFOLD) < 0) {
+    return a;
+  }
 
   int fold_codepoint_utf = utf_ptr2char((char *)fold_str_utf);
 
diff --git a/test/unit/mbyte_spec.lua b/test/unit/mbyte_spec.lua
index 62390c8794..e0c0244989 100644
--- a/test/unit/mbyte_spec.lua
+++ b/test/unit/mbyte_spec.lua
@@ -347,4 +347,10 @@ describe('mbyte', function()
     check('L̓̉̑̒̌̚ơ̗̌̒̄̀ŕ̈̈̎̐̕è̇̅̄̄̐m̖̟̟̅̄̚', {'L̓̉̑̒̌̚', 'ơ̗̌̒̄̀', 'ŕ̈̈̎̐̕', 'è̇̅̄̄̐', 'm̖̟̟̅̄̚'})
     -- stylua: ignore end
   end)
+
+  describe('utf_fold', function()
+    itp('does not crash with surrogates #30527', function()
+      eq(0xDDFB, lib.utf_fold(0xDDFB))
+    end)
+  end)
 end)