gosxcontenttype.m compile failure with -Werror=declaration-after-statement

conda-forge is seeing a compile failure on macOS due to the declaration-after-statement Werror flag:

x86_64-apple-darwin13.4.0-clang [...]  -Werror=declaration-after-statement [...] -c ../gio/gosxcontenttype.m
../gio/gosxcontenttype.m:63:11: error: mixing declarations and code is incompatible with standards before C99 [-Werror,-Wdeclaration-after-statement]
  CFIndex length = CFStringGetLength (str);

This is with Clang 14.0.4.