[libc] Remove global constructor in getopt implementation

This file required a global constructor due to copying the file stream
and have a non-constexpr constructor for the wrapper type. Also, I
changes the `opterr` to be a pointer, because it seemed like it wasn't
being set correctly as an externally visibile variable if we just
captured it by value.

Reviewed By: abrachet

Differential Revision: https://reviews.llvm.org/D155766

Author: jhuber6

libc/src/unistd/getopt.cpp

@@ -22,7 +22,6 @@
 namespace __llvm_libc {
 
 template <typename T> struct RefWrapper {
-  RefWrapper(T *ptr) : ptr(ptr) {}
   RefWrapper &operator=(const RefWrapper &) = default;
   operator T &() { return *ptr; }
   T &get() { return *ptr; }
@@ -35,15 +34,17 @@ struct GetoptContext {
   RefWrapper<int> optopt;
   RefWrapper<unsigned> optpos;
 
-  int opterr;
+  RefWrapper<int> opterr;
 
   FILE *errstream;
 
   GetoptContext &operator=(const GetoptContext &) = default;
 
   template <typename... Ts> void report_error(const char *fmt, Ts... ts) {
     if (opterr)
-      __llvm_libc::fprintf(errstream, fmt, ts...);
+      __llvm_libc::fprintf(
+          errstream ? errstream : reinterpret_cast<FILE *>(__llvm_libc::stderr),
+          fmt, ts...);
   }
 };
 
@@ -171,25 +172,21 @@ int getopt_r(int argc, char *const argv[], const char *optstring,
 namespace impl {
 
 extern "C" {
-
 char *optarg = nullptr;
 int optind = 1;
 int optopt = 0;
 int opterr = 0;
-
 }
 
 static unsigned optpos;
 
-static GetoptContext ctx{
-    &impl::optarg, &impl::optind,
-    &impl::optopt, &optpos,
-    impl::opterr,  reinterpret_cast<FILE *>(__llvm_libc::stderr)};
+static GetoptContext ctx{&impl::optarg, &impl::optind, &impl::optopt,
+                         &optpos,       &impl::opterr, /*errstream=*/nullptr};
 
 #ifndef LIBC_COPT_PUBLIC_PACKAGING
 // This is used exclusively in tests.
 void set_getopt_state(char **optarg, int *optind, int *optopt, unsigned *optpos,
-                      int opterr, FILE *errstream) {
+                      int *opterr, FILE *errstream) {
   ctx = {optarg, optind, optopt, optpos, opterr, errstream};
 }
 #endif

libc/src/unistd/getopt.h

@@ -15,7 +15,7 @@
 namespace __llvm_libc {
 
 namespace impl {
-void set_getopt_state(char **, int *, int *, unsigned *, int, FILE *);
+void set_getopt_state(char **, int *, int *, unsigned *, int *, FILE *);
 }
 
 int getopt(int argc, char *const argv[], const char *optstring);

libc/test/src/unistd/getopt_test.cpp

@@ -31,7 +31,7 @@ unsigned optpos;
 void set_state(FILE *errstream) {
   __llvm_libc::impl::set_getopt_state(
       &test_globals::optarg, &test_globals::optind, &test_globals::optopt,
-      &test_globals::optpos, test_globals::opterr, errstream);
+      &test_globals::optpos, &test_globals::opterr, errstream);
 }
 
 // TODO: <stdio> could be either llvm-libc's or the system libc's. The former