curl_easy_setopt type checking failed

[locpyl-tidnyd]

I am calling curl_easy_setopt to set an SSL context callback to use an in-memory CA store. My callback is declared as

static CURLcode
_curl_ssl_ctx_cb(CURL* curl, SSL_CTX* sslctx, void* param)

to avoid gratuitous casting from void* to SSL_CTX*. GCC 10.2.0 compiles this without warnings on -O0, but with optimization enabled it produces a typecheck warning:

In file included from ../curl/include/curl/curl.h:3024,
                 from daemon/main.c:17:
daemon/main.c: In function '_setup_ssl_curl':
../curl/include/curl/typecheck-gcc.h:80:13: warning: call to '_curl_easy_setopt_err_ssl_ctx_cb' declared with attribute warning: curl_easy_setopt expects a curl_ssl_ctx_callback argument for this option [-Wattribute-warning]
   80 |             _curl_easy_setopt_err_ssl_ctx_cb();                         \
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../curl/include/curl/typecheck-gcc.h:80:13: note: in definition of macro 'curl_easy_setopt'
   80 |             _curl_easy_setopt_err_ssl_ctx_cb();                         \
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

and of course with -Werror on compilation fails. Confusingly, GCC 9.3.0 on Linux compiles the same input without warnings regardless of optimization setting. The root cause appears to be that the callback declarations in curl/typecheck-gcc.h take SSL_CTX by value, whereas the actual callsite passes the SSL context by pointer, as it should (since SSL_CTX is an opaque struct). This issue is similar to #5432.

curl/libcurl version

libcurl 7.75.0

operating system

MINGW64_NT-10.0-1xxxxx REDACTED x86_64 Msys
gcc.exe (Rev9, Built by MSYS2 project) 10.2.0

[bagder]

To be clear, that's setting the CURLOPT_SSL_CTX_FUNCTION right?