[libc++] Enable -Wmissing-prototypes

libcxx/include/fstream

@@ -221,7 +221,7 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#    if _LIBCPP_STD_VER >= 26 && defined(_LIBCPP_WIN32API)
+#    if _LIBCPP_STD_VER >= 23 && defined(_LIBCPP_WIN32API)
 _LIBCPP_EXPORTED_FROM_ABI void* __filebuf_windows_native_handle(FILE* __file) noexcept;
 #    endif
 

libcxx/src/charconv.cpp

@@ -18,9 +18,12 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace __itoa {
 
+_LIBCPP_DIAGNOSTIC_PUSH
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wmissing-prototypes")
+// These functions exist for ABI compatibility, so we don't ever want a declaration prior to the definition.
 _LIBCPP_EXPORTED_FROM_ABI char* __u32toa(uint32_t value, char* buffer) noexcept { return __base_10_u32(buffer, value); }
-
 _LIBCPP_EXPORTED_FROM_ABI char* __u64toa(uint64_t value, char* buffer) noexcept { return __base_10_u64(buffer, value); }
+_LIBCPP_DIAGNOSTIC_POP
 
 } // namespace __itoa
 

libcxx/src/experimental/time_zone.cpp

@@ -720,7 +720,7 @@ __get_sys_info(sys_seconds __time,
 // Iff the "offsets" are the same '__current.__end' is replaced with
 // '__next.__end', which effectively merges the two objects in one object. The
 // function returns true if a merge occurred.
-[[nodiscard]] bool __merge_continuation(sys_info& __current, const sys_info& __next) {
+[[nodiscard]] static bool __merge_continuation(sys_info& __current, const sys_info& __next) {
   if (__current.end != __next.begin)
     return false;
 

libcxx/src/experimental/tzdb.cpp

@@ -49,6 +49,8 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace chrono {
 
+_LIBCPP_DIAGNOSTIC_PUSH
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wmissing-prototypes")
 // This function is weak so it can be overriden in the tests. The
 // declaration is in the test header test/support/test_tzdb.h
 _LIBCPP_WEAK string_view __libcpp_tzdb_directory() {
@@ -58,6 +60,7 @@ _LIBCPP_WEAK string_view __libcpp_tzdb_directory() {
 #  error "unknown path to the IANA Time Zone Database"
 #endif
 }
+_LIBCPP_DIAGNOSTIC_POP
 
 //===----------------------------------------------------------------------===//
 //                           Details

libcxx/src/filesystem/int128_builtins.cpp

@@ -16,6 +16,8 @@
 #include <__config>
 #include <climits>
 
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wmissing-prototypes") // See the FIXME above
+
 #if _LIBCPP_HAS_INT128
 
 extern "C" __attribute__((no_sanitize("undefined"))) _LIBCPP_EXPORTED_FROM_ABI __int128_t

libcxx/src/include/from_chars_floating_point.h

@@ -197,7 +197,7 @@ struct __exponent_result {
 // __offset, 0, false. This allows using the results unconditionally, the
 // __present is important for the scientific notation, where the value is
 // mandatory.
-__exponent_result __parse_exponent(const char* __input, size_t __n, size_t __offset, char __marker) {
+static __exponent_result __parse_exponent(const char* __input, size_t __n, size_t __offset, char __marker) {
   if (__offset + 1 < __n &&                          // an exponent always needs at least one digit.
       std::tolower(__input[__offset]) == __marker && //
       !std::isspace(__input[__offset + 1])           // leading whitespace is not allowed.
@@ -217,7 +217,7 @@ __exponent_result __parse_exponent(const char* __input, size_t __n, size_t __off
 }
 
 // Here we do this operation as int64 to avoid overflow.
-int32_t __merge_exponents(int64_t __fractional, int64_t __exponent, int __max_biased_exponent) {
+static int32_t __merge_exponents(int64_t __fractional, int64_t __exponent, int __max_biased_exponent) {
   int64_t __sum = __fractional + __exponent;
 
   if (__sum > __max_biased_exponent)

libcxx/src/support/win32/compiler_rt_shims.cpp

@@ -14,6 +14,8 @@
 #include <cmath>
 #include <complex>
 
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wmissing-prototypes") // See comment above
+
 template <class T>
 static std::__complex_t<T> mul_impl(T a, T b, T c, T d) {
   T __ac = a * c;

libcxx/src/support/win32/locale_win32.cpp

@@ -144,7 +144,7 @@ int __snprintf(char* ret, size_t n, __locale_t loc, const char* format, ...) {
 // Like sprintf, but when return value >= 0 it returns
 // a pointer to a malloc'd string in *sptr.
 // If return >= 0, use free to delete *sptr.
-int __libcpp_vasprintf(char** sptr, const char* __restrict format, va_list ap) {
+static int __libcpp_vasprintf(char** sptr, const char* __restrict format, va_list ap) {
   *sptr = nullptr;
   // Query the count required.
   va_list ap_copy;

libcxxabi/src/cxa_personality.cpp

@@ -62,6 +62,11 @@
 #  define __ptrauth_scan_results_landingpad_intptr
 #endif
 
+// The functions defined in this file are magic functions called only by the compiler.
+#ifdef __clang__
+#  pragma clang diagnostic ignored "-Wmissing-prototypes"
+#endif
+
 // TODO: This is a temporary workaround for libc++abi to recognize that it's being
 // built against LLVM's libunwind. LLVM's libunwind started reporting _LIBUNWIND_VERSION
 // in LLVM 15 -- we can remove this workaround after shipping LLVM 17. Once we remove

libcxxabi/src/cxa_thread_atexit.cpp

@@ -106,6 +106,7 @@ namespace {
 
 #endif // HAVE___CXA_THREAD_ATEXIT_IMPL
 
+#if defined(__linux__) || defined(__Fuchsia__)
 extern "C" {
 
   _LIBCXXABI_FUNC_VIS int __cxa_thread_atexit(Dtor dtor, void* obj, void* dso_symbol) throw() {
@@ -140,6 +141,7 @@ extern "C" {
     }
 #endif // HAVE___CXA_THREAD_ATEXIT_IMPL
   }
+#endif // defined(__linux__) || defined(__Fuchsia__)
 
 } // extern "C"
 } // namespace __cxxabiv1

libcxxabi/src/private_typeinfo.cpp

@@ -831,6 +831,10 @@ bool __pointer_to_member_type_info::can_catch_nested(
 #pragma clang diagnostic ignored "-Wmissing-field-initializers"
 #endif
 
+#pragma GCC diagnostic push
+// __dynamic_cast is called by the compiler, so there is no prototype
+#pragma GCC diagnostic ignored "-Wmissing-prototypes"
+
 // __dynamic_cast
 
 // static_ptr: pointer to an object of type static_type; nonnull, and since the
@@ -953,6 +957,8 @@ __dynamic_cast(const void *static_ptr, const __class_type_info *static_type,
     return const_cast<void*>(dst_ptr);
 }
 
+#pragma GCC diagnostic pop
+
 #ifdef __clang__
 #pragma clang diagnostic pop
 #endif

libunwind/include/unwind_arm_ehabi.h

@@ -126,7 +126,7 @@ _Unwind_VRS_Pop(_Unwind_Context *context, _Unwind_VRS_RegClass regclass,
                 _Unwind_VRS_DataRepresentation representation);
 
 #if defined(_LIBUNWIND_UNWIND_LEVEL1_EXTERNAL_LINKAGE)
-#define _LIBUNWIND_EXPORT_UNWIND_LEVEL1 extern
+#define _LIBUNWIND_EXPORT_UNWIND_LEVEL1 extern __inline__
 #else
 #define _LIBUNWIND_EXPORT_UNWIND_LEVEL1 static __inline__
 #endif

libunwind/include/unwind_itanium.h

@@ -69,6 +69,9 @@ extern void _Unwind_SetGR(struct _Unwind_Context *context, int index,
 extern uintptr_t _Unwind_GetIP(struct _Unwind_Context *context);
 extern void _Unwind_SetIP(struct _Unwind_Context *, uintptr_t new_value);
 
+extern _Unwind_Reason_Code __gnu_unwind_frame(_Unwind_Exception *,
+                                              struct _Unwind_Context *);
+
 #ifdef __cplusplus
 }
 #endif

libunwind/src/Unwind-EHABI.cpp

@@ -23,6 +23,7 @@
 #include "config.h"
 #include "libunwind.h"
 #include "libunwind_ext.h"
+#include "unwind_itanium.h"
 #include "unwind.h"
 
 namespace {

libunwind/src/UnwindLevel1.c

@@ -200,7 +200,6 @@ unwind_phase1(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *except
   }
   return _URC_NO_REASON;
 }
-extern int __unw_step_stage2(unw_cursor_t *);
 
 #if defined(_LIBUNWIND_USE_GCS)
 // Enable the GCS target feature to permit gcspop instructions to be used.

libunwind/src/Unwind_AIXExtras.cpp

@@ -10,6 +10,7 @@
 // This file is only used for AIX.
 #if defined(_AIX)
 
+#include "AddressSpace.hpp"
 #include "config.h"
 #include "libunwind_ext.h"
 #include <sys/debug.h>

libunwind/src/libunwind_ext.h

@@ -26,6 +26,7 @@ extern "C" {
 extern int __unw_getcontext(unw_context_t *);
 extern int __unw_init_local(unw_cursor_t *, unw_context_t *);
 extern int __unw_step(unw_cursor_t *);
+extern int __unw_step_stage2(unw_cursor_t *);
 extern int __unw_get_reg(unw_cursor_t *, unw_regnum_t, unw_word_t *);
 extern int __unw_get_fpreg(unw_cursor_t *, unw_regnum_t, unw_fpreg_t *);
 extern int __unw_set_reg(unw_cursor_t *, unw_regnum_t, unw_word_t);

runtimes/cmake/Modules/WarningFlags.cmake

@@ -26,6 +26,7 @@ function(cxx_add_warning_flags target enable_werror enable_pedantic)
       -Wzero-length-array
       -Wdeprecated-redundant-constexpr-static-def
       -Wno-nullability-completeness
+      -Wmissing-prototypes
       )
 
   if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")