src: ignore GCC -Wcast-function-type for v8.h

[danbev]

Currently, the following warnings are emitted during compilation:

In file included from ../src/string_bytes.h:29,
                 from ../src/string_bytes.cc:22:
../deps/v8/include/v8.h:
In instantiation of ‘void v8::PersistentBase<T>::SetWeak(
    P*,typename v8::WeakCallbackInfo<P>::Callback, v8::WeakCallbackType)
[with P = node::BaseObject;
T = v8::Object;
typename v8::WeakCallbackInfo<P>::Callback =
    void (*)(const v8::WeakCallbackInfo<node::BaseObject>&)]’:
../src/base_object-inl.h:135:42:   required from here
../deps/v8/include/v8.h:10732:16: warning:
cast between incompatible function types from
‘v8::WeakCallbackInfo<node::BaseObject>::Callback’ {aka
‘void (*)(const v8::WeakCallbackInfo<node::BaseObject>&)’} to
‘Callback’ {aka ‘void (*)(const v8::WeakCallbackInfo<void>&)’}
[-Wcast-function-type]
10732 |                reinterpret_cast<Callback>(callback), type);
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

And the same from test/cctest/test_aliased_buffer.cc

We have an open pull request against v8 for this:
https://chromium-review.googlesource.com/c/v8/v8/+/2080361

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/30492/

[bnoordhuis]

How does that work? We include v8.h in numerous places, not just those two files. It also wouldn't silence the warnings when building V8 itself, right?

Apropos the V8 CL, you picked Yang as a reviewer but I don't think he is on the V8 team anymore.

[danbev]

How does that work? We include v8.h in numerous places, not just those two files.

We have previously added these kinda of ignores in 3ff2aec. At that point in time I only focused on the ones that were being generated. Hopefully this is only temporary and this will be added in upstream v8.

It also wouldn't silence the warnings when building V8 itself, right?

As far as I can tell -Wcast-function-type is not specified when building V8, so these warnings are not generated for V8 itself. For example, looking at the generated make file out/tools/v8_gypfiles/v8_base_without_compiler.target.mk it has the following CFLAGS defined:

CFLAGS_Release := \                                                             
        -pthread \                                                              
        -Wno-unused-parameter \                                                 
        -m64 \                                                                  
        -Wno-return-type \                                                      
        -fno-strict-aliasing \                                                  
        -m64 \                                                                  
        -O3 \                                                                   
        -fno-omit-frame-pointer \                                               
        -fdata-sections \                                                       
        -ffunction-sections \                                                   
         \                                                                      
        -O3 

Adding -Wcast-function-type allows these warning to be generated when building V8.

Apropos the V8 CL, you picked Yang as a reviewer but I don't think he is on the V8 team anymore.

Thanks, I've updated it now and added someone else.

[bnoordhuis]

-Wcast-function-type is not specified when building V8

Oh, I understand now - it's stripped from cflags (-Wextra implies -Wcast-function-type):

node/tools/v8_gypfiles/toolchain.gypi

Line 171 in 6ed912d

'cflags!': [ '-Wall', '-Wextra' ],

I'm good with the pragma approach if it's temporary.

[danbev]

Re-run of failing node-test-commit-linux ✔️
Re-run of failing node-test-commit-arm-fanned ✔️
Re-run of failing /node-test-commit-osx ✔️
Re-run of failing node-test-commit-linux-containered ✔️

[danbev]

Landed in f21cf45.