cmake: Avoid MSVC C4273 warnings in send/recv checks
We use `check_c_source_compiles` to check possible send/recv signatures
by reproducing the forward declarations from system headers. On Windows
the `winsock2.h` header adds dll linkage settings to its forward
declaration. If ours does not match the compiler warns:
warning C4273: 'recv': inconsistent dll linkage
Add `WINSOCK_API_LINKAGE` to our test signatures when it is defined so
that our linkage is consistent with that from `winsock2.h`.
Fixes #4764
Closes #5232
diff --git a/CMake/OtherTests.cmake b/CMake/OtherTests.cmake
index f3b92d5..7cec6da 100644
--- a/CMake/OtherTests.cmake
+++ b/CMake/OtherTests.cmake
@@ -63,6 +63,9 @@
unset(curl_cv_func_recv_test CACHE)
check_c_source_compiles("
${_source_epilogue}
+ #ifdef WINSOCK_API_LINKAGE
+ WINSOCK_API_LINKAGE
+ #endif
extern ${recv_retv} ${signature_call_conv}
recv(${recv_arg1}, ${recv_arg2}, ${recv_arg3}, ${recv_arg4});
int main(void) {
@@ -127,6 +130,9 @@
unset(curl_cv_func_send_test CACHE)
check_c_source_compiles("
${_source_epilogue}
+ #ifdef WINSOCK_API_LINKAGE
+ WINSOCK_API_LINKAGE
+ #endif
extern ${send_retv} ${signature_call_conv}
send(${send_arg1}, ${send_arg2}, ${send_arg3}, ${send_arg4});
int main(void) {