Enabling (use_standard_c_and_cxx_flags) fails when paired with C++ stubs on Windows

[kit-ty-kate]

Expected Behavior

For (foreign_stubs (language cxx) ...) to work on Windows

Actual Behavior

Flexlink fails with "Does not know about the -shared-libgcc argument"

Reproduction

1. Create a library with a C++ foreign stubs
2. Build it on Windows (MinGW)

Specifications

• Version of dune (output of dune --version): 3.5.0
• Version of ocaml (output of ocamlc --version): 4.14.1
• Operating system (distribution and version): Windows / x86_64 / MinGW

[rgrinberg]

What does ocamlc -config say on this system?

[kit-ty-kate]

version: 4.14.1
standard_library_default: C:/cygwin64/home/Kate/opam/bootstrap/ocaml/lib/ocaml
standard_library: C:/cygwin64/home/Kate/opam/bootstrap/ocaml/lib/ocaml
ccomp_type: cc
c_compiler: x86_64-w64-mingw32-gcc
ocamlc_cflags: -O2 -fno-strict-aliasing -fwrapv -mms-bitfields
ocamlc_cppflags:
ocamlopt_cflags: -O2 -fno-strict-aliasing -fwrapv -mms-bitfields
ocamlopt_cppflags:
bytecomp_c_compiler: x86_64-w64-mingw32-gcc -O2 -fno-strict-aliasing -fwrapv -mm
s-bitfields
native_c_compiler: x86_64-w64-mingw32-gcc -O2 -fno-strict-aliasing -fwrapv -mms-
bitfields
bytecomp_c_libraries: -lws2_32 -lversion
native_c_libraries: -lws2_32 -lversion
native_pack_linker: x86_64-w64-mingw32-ld -r -o
architecture: amd64
model: default
int_size: 63
word_size: 64
system: mingw64
asm: x86_64-w64-mingw32-gcc -c
asm_cfi_supported: false
with_frame_pointers: false
ext_exe: .exe
ext_obj: .o
ext_asm: .s
ext_lib: .a
ext_dll: .dll
os_type: Win32
default_executable_name: camlprog.exe
systhread_supported: true
host: x86_64-w64-mingw32
target: x86_64-w64-mingw32
flambda: false
safe_string: true
default_safe_string: true
flat_float_array: true
function_sections: false
afl_instrument: false
windows_unicode: true
supports_shared_libraries: true
naked_pointers: true
exec_magic_number: Caml1999X031
cmi_magic_number: Caml1999I031
cmo_magic_number: Caml1999O031
cma_magic_number: Caml1999A031
cmx_magic_number: Caml1999Y031
cmxa_magic_number: Caml1999Z031
ast_impl_magic_number: Caml1999M031
ast_intf_magic_number: Caml1999N031
cmxs_magic_number: Caml1999D031
cmt_magic_number: Caml1999T031
linear_magic_number: Caml1999L031

[rgrinberg]

No idea, sorry. What's the version of mingw here?

@nojb any idea why mingw doesn't like this option?

[nojb]

No idea, sorry. What's the version of mingw here?

@nojb any idea why mingw doesn't like this option?

I am far from an expert, but on Windows, my believe that libgcc is linked dynamically by default, so perhaps this flag just does not exist. Just omitting the flag may be a first step to make it work (but maybe other steps are needed).

[kit-ty-kate]

the problem is that on Windows with flexlink, it is flexlink that is called as the linker by the compiler, not gcc directly. -shared-libgcc is not a correct option of flexlink and any option that is meant to be given to gcc instead has to have the -Wl, prefix instead (e.g. -Wl,-the-option).