[Bug c++/90010] [8/9 Regression] valgrind error with snprintf and -Wall

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90010

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 46113
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46113&action=edit
gcc9-pr90010.patch

Untested fix.