[libcxx] [libcxxabi] [libunwind] [llvm] [libc++] Enable -Wmissing-prototypes (PR #116261)

[Nikolas Klauser via cfe-commits]

https://github.com/philnik777 updated https://github.com/llvm/llvm-project/pull/116261

>From e6f36baf39d1c3e2d90c3343c49771ccf1ca976c Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Thu, 14 Nov 2024 18:30:39 +0100
Subject: [PATCH] [libc++] Enable -Wmissing-prototypes

---
 libcxx/src/charconv.cpp                        | 5 ++++-
 libcxx/src/filesystem/int128_builtins.cpp      | 2 ++
 libcxx/src/include/from_chars_floating_point.h | 4 ++--
 libcxx/src/legacy_pointer_safety.cpp           | 4 ++++
 libcxxabi/src/cxa_personality.cpp              | 5 +++++
 libcxxabi/src/private_typeinfo.cpp             | 6 ++++++
 libunwind/src/UnwindLevel1.c                   | 1 -
 libunwind/src/libunwind_ext.h                  | 1 +
 runtimes/cmake/Modules/WarningFlags.cmake      | 1 +
 9 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/libcxx/src/charconv.cpp b/libcxx/src/charconv.cpp
index 5e8cb7d97703b4..4621df05066997 100644
--- a/libcxx/src/charconv.cpp
+++ b/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.
 _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
 
diff --git a/libcxx/src/filesystem/int128_builtins.cpp b/libcxx/src/filesystem/int128_builtins.cpp
index da6f39e7d78b60..e811b3e6f912db 100644
--- a/libcxx/src/filesystem/int128_builtins.cpp
+++ b/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
diff --git a/libcxx/src/include/from_chars_floating_point.h b/libcxx/src/include/from_chars_floating_point.h
index 19eeeb28fb08d2..81d2180cc94805 100644
--- a/libcxx/src/include/from_chars_floating_point.h
+++ b/libcxx/src/include/from_chars_floating_point.h
@@ -193,7 +193,7 @@ 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.
@@ -213,7 +213,7 @@ __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)
diff --git a/libcxx/src/legacy_pointer_safety.cpp b/libcxx/src/legacy_pointer_safety.cpp
index a9361ca879bb58..31abc978499006 100644
--- a/libcxx/src/legacy_pointer_safety.cpp
+++ b/libcxx/src/legacy_pointer_safety.cpp
@@ -15,9 +15,13 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+_LIBCPP_DIAGNOSTIC_PUSH
+_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wmissing-prototypes")
+// These functions exist for ABI compatibility, so we don't ever want a declaration.
 _LIBCPP_EXPORTED_FROM_ABI void declare_reachable(void*) {}
 _LIBCPP_EXPORTED_FROM_ABI void declare_no_pointers(char*, size_t) {}
 _LIBCPP_EXPORTED_FROM_ABI void undeclare_no_pointers(char*, size_t) {}
 _LIBCPP_EXPORTED_FROM_ABI void* __undeclare_reachable(void* p) { return p; }
+_LIBCPP_DIAGNOSTIC_POP
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxxabi/src/cxa_personality.cpp b/libcxxabi/src/cxa_personality.cpp
index 5f6e75c5be19ce..1836fba5ab5dd5 100644
--- a/libcxxabi/src/cxa_personality.cpp
+++ b/libcxxabi/src/cxa_personality.cpp
@@ -22,6 +22,11 @@
 #include "private_typeinfo.h"
 #include "unwind.h"
 
+// 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
diff --git a/libcxxabi/src/private_typeinfo.cpp b/libcxxabi/src/private_typeinfo.cpp
index 2f631041f74c94..5252deb012ad11 100644
--- a/libcxxabi/src/private_typeinfo.cpp
+++ b/libcxxabi/src/private_typeinfo.cpp
@@ -832,6 +832,10 @@ 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
@@ -954,6 +958,8 @@ __dynamic_cast(const void *static_ptr, const __class_type_info *static_type,
     return const_cast<void*>(dst_ptr);
 }
 
+#pragma GCC diagnostic push
+
 #ifdef __clang__
 #pragma clang diagnostic pop
 #endif
diff --git a/libunwind/src/UnwindLevel1.c b/libunwind/src/UnwindLevel1.c
index 7e785f4d31e716..e7e2b6ef624dce 100644
--- a/libunwind/src/UnwindLevel1.c
+++ b/libunwind/src/UnwindLevel1.c
@@ -181,7 +181,6 @@ 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.
diff --git a/libunwind/src/libunwind_ext.h b/libunwind/src/libunwind_ext.h
index 28db43a4f6eef2..306ed41b3db631 100644
--- a/libunwind/src/libunwind_ext.h
+++ b/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);
diff --git a/runtimes/cmake/Modules/WarningFlags.cmake b/runtimes/cmake/Modules/WarningFlags.cmake
index d17bf92389d0b0..15e6772c2fae98 100644
--- a/runtimes/cmake/Modules/WarningFlags.cmake
+++ b/runtimes/cmake/Modules/WarningFlags.cmake
@@ -25,6 +25,7 @@ function(cxx_add_warning_flags target enable_werror enable_pedantic)
       -Wformat-nonliteral
       -Wzero-length-array
       -Wdeprecated-redundant-constexpr-static-def
+      -Wmissing-prototypes
       )
 
   if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")