From 6f8984c89a0e85a056d773484b3dcf97f30f1a21 Mon Sep 17 00:00:00 2001
From: Joyee Cheung <joyeec9h3@gmail.com>
Date: Thu, 5 Nov 2026 15:32:49 +0100
Subject: [PATCH] build: fix GCC warnings when building V8 with gnu++20
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This silences the following warning from GCC:

- deps/v8/src/base/flags.h: call to non-constexpr function
  `std::__atomic_base<unsigned char>::operator unsigned char() const`
  in the defaulted `constexpr Flags::operator==` when instantiated
  with `std::atomic<uint8_t>` storage [-Winvalid-constexpr]
- deps/v8/include/v8-wasm.h: call to non-constexpr function
  `std::unique_ptr<const unsigned char[]>::get() const` in
  `constexpr OwnedBuffer::as_span()` [-Winvalid-constexpr]
- deps/v8/src/execution/simulator.h: ‘nodebug’ attribute directive
  ignored [-Wattributes]

Also move -fvisibility-inlines-hidden from cflags to cflags_cc in
tools/v8_gypfiles/v8.gyp to fix the following warning.

  cc1: warning: command-line option '-fvisibility-inlines-hidden' is
  valid for C++/ObjC++ but not for C

Signed-off-by: Joyee Cheung <joyeec9h3@gmail.com>
---
 node.gyp                         | 3 +++
 tools/v8_gypfiles/toolchain.gypi | 7 +++++++
 tools/v8_gypfiles/v8.gyp         | 2 ++
 3 files changed, 12 insertions(+)

diff --git a/node.gyp b/node.gyp
index 714609b03e66..eddac01f1e13 100644
--- a/node.gyp
+++ b/node.gyp
@@ -558,6 +558,9 @@
     'conditions': [
       ['clang==0 and OS!="win"', {
         'cflags': [ '-Wno-restrict', ],
+        'cflags_cc': [
+          '-Wno-invalid-constexpr',
+        ],
       }],
       # TODO(joyeecheung): investigate if it breaks addons.
       # ['OS=="mac"', {
diff --git a/tools/v8_gypfiles/toolchain.gypi b/tools/v8_gypfiles/toolchain.gypi
index 058580f2ab42..645f19ca5c9f 100644
--- a/tools/v8_gypfiles/toolchain.gypi
+++ b/tools/v8_gypfiles/toolchain.gypi
@@ -122,6 +122,13 @@
           # On by default in Clang and V8 requires it at least for arm64.
           '-flax-vector-conversions',
         ],
+        'cflags_cc': [
+          # TODO(joyeecheung): this may be removed after we switch to C++23
+          '-Wno-invalid-constexpr',
+          # V8 uses the clang-only nodebug attribute in
+          # src/execution/simulator.h, which GCC ignores with a warning.
+          '-Wno-attributes',
+        ],
       }],
       ['clang==1 or OS!="win"', {
         'cflags_cc': [
diff --git a/tools/v8_gypfiles/v8.gyp b/tools/v8_gypfiles/v8.gyp
index 71b6772bc345..d7143a86acb4 100644
--- a/tools/v8_gypfiles/v8.gyp
+++ b/tools/v8_gypfiles/v8.gyp
@@ -77,6 +77,8 @@
       }, '(OS!="aix" and OS!="os400") and (OS!="win" or clang==1)', {
         'cflags': [
           '-fvisibility=hidden',
+        ],
+        'cflags_cc': [
           '-fvisibility-inlines-hidden'
         ],
       }],  # MSVC hides the non-public symbols by default so no need to configure it.