[libc] Minor test signedness fixes

[ddcc]

Summary

Resolve compiler warnings about signed conversion

[abrachet]

libc/utils/testutils/ExecuteFunction.h

27

I don't know why I ever made that uinptr that doesn't really make sense. Would you mind changing it while you're here?

44

libc/test/src/threads/cnd_test.cpp

 constexpr unsigned int THRD_COUNT = 10000;
 
 static __llvm_libc::cpp::Atomic<unsigned int> broadcast_count(0);
 static cnd_t broadcast_cnd, threads_ready_cnd;
 static mtx_t broadcast_mtx, threads_ready_mtx;
 
 int broadcast_thread_func(void *) {
   __llvm_libc::mtx_lock(&broadcast_mtx);
-  int oldval = broadcast_count.fetch_add(1);
+  unsigned oldval = broadcast_count.fetch_add(1);
   if (oldval == THRD_COUNT - 1) {
     __llvm_libc::mtx_lock(&threads_ready_mtx);
     __llvm_libc::cnd_signal(&threads_ready_cnd);
     __llvm_libc::mtx_unlock(&threads_ready_mtx);
   }
 
   __llvm_libc::cnd_wait(&broadcast_cnd, &broadcast_mtx);
   __llvm_libc::mtx_unlock(&broadcast_mtx);

libc/utils/testutils/ExecuteFunction.h

public:
   virtual ~FunctionCaller() {}
   virtual void operator()() = 0;
 };
 
 struct ProcessStatus {
   int platform_defined;
   const char *failure = nullptr;
 
-  static constexpr uintptr_t TIMEOUT = -1L;
+  static constexpr unsigned TIMEOUT = ~0U;
 
   static ProcessStatus error(const char *error) { return {0, error}; }
   static ProcessStatus timed_out_ps() {
     return {0, reinterpret_cast<const char *>(TIMEOUT)};
   }
 
   bool timed_out() const {
     return failure == reinterpret_cast<const char *>(TIMEOUT);
   }
   const char *get_error() const { return timed_out() ? nullptr : failure; }
   bool exited_normally() const;
   int get_exit_code() const;
   int get_fatal_signal() const;
 };
 
 ProcessStatus invoke_in_subprocess(FunctionCaller *func,
-                                   unsigned timeout_ms = -1);
+                                   unsigned timeout_ms = TIMEOUT);
 
 const char *signal_as_string(int signum);
 
 } // namespace testutils
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_UTILS_TESTUTILS_EXECUTEFUNCTION_H