The code changes seem fine, but I don't think a testcase should depend on the details of what system strings.h declares (or even that it exists) like that. If you want a system header declaration, add a header to the testsuite that uses #pragma GCC system_header to be sure it's handled as such, and include that header in the testcase; there are several existing examples of this in gcc.dg.
-- Joseph S. Myers jos...@codesourcery.com
