Build warnings with Gcc8

[rikardfalkeborn]

I did this

Built curl with Gcc 8.

$ ./buildconf
$ ./configure --enable-debug --enable-warnings --enable-werror CC=gcc
$ make

I expected the following

Successful build, instead I got this:

md5.c:489:5: error: cast between incompatible function types from ‘int (*)(MD5_CTX *)’ {aka ‘int (*)(struct MD5state_st *)’} to ‘void (*)(void *)’ [-Werror=cast-function-type]
     (HMAC_hinit_func) MD5_Init,           /* Hash initialization function. */
     ^
md5.c:490:5: error: cast between incompatible function types from ‘int (*)(MD5_CTX *, const void *, size_t)’ {aka ‘int (*)(struct MD5state_st *, const void *, long unsigned int)’} to ‘void (*)(void *, const unsigned char *, unsigned int)’ [-Werror=cast-function-type]
     (HMAC_hupdate_func) MD5_Update,       /* Hash update function. */
     ^
md5.c:491:5: error: cast between incompatible function types from ‘int (*)(unsigned char *, MD5_CTX *)’ {aka ‘int (*)(unsigned char *, struct MD5state_st *)’} to ‘void (*)(unsigned char *, void *)’ [-Werror=cast-function-type]
     (HMAC_hfinal_func) MD5_Final,         /* Hash computation end function. */
     ^
md5.c:500:5: error: cast between incompatible function types from ‘int (*)(MD5_CTX *)’ {aka ‘int (*)(struct MD5state_st *)’} to ‘void (*)(void *)’ [-Werror=cast-function-type]
     (Curl_MD5_init_func) MD5_Init,      /* Digest initialization function */
     ^
md5.c:501:5: error: cast between incompatible function types from ‘int (*)(MD5_CTX *, const void *, size_t)’ {aka ‘int (*)(struct MD5state_st *, const void *, long unsigned int)’} to ‘void (*)(void *, const unsigned char *, unsigned int)’ [-Werror=cast-function-type]
     (Curl_MD5_update_func) MD5_Update,  /* Digest update function */
     ^
md5.c:502:5: error: cast between incompatible function types from ‘int (*)(unsigned char *, MD5_CTX *)’ {aka ‘int (*)(unsigned char *, struct MD5state_st *)’} to ‘void (*)(unsigned char *, void *)’ [-Werror=cast-function-type]
     (Curl_MD5_final_func) MD5_Final,    /* Digest computation end function */
     ^
cc1: all warnings being treated as errors
make[2]: *** [Makefile:1558: libcurl_la-md5.lo] Error 1
http2.c: In function ‘http2_connisdead’:
http2.c:208:18: error: cast between incompatible function types from ‘recving’ {aka ‘int (*)(void)’} to ‘ssize_t (*)(struct connectdata *, int,  char *, size_t,  CURLcode *)’ {aka ‘long int (*)(struct connectdata *, int,  char *, long unsigned int,  enum <anonymous> *)’} [-Werror=cast-function-type]
         nread = ((Curl_recv *)httpc->recv_underlying)(
                  ^
http2.c: In function ‘send_callback’:
http2.c:368:14: error: cast between incompatible function types from ‘sending’ {aka ‘int (*)(void)’} to ‘ssize_t (*)(struct connectdata *, int,  const void *, size_t,  CURLcode *)’ {aka ‘long int (*)(struct connectdata *, int,  const void *, long unsigned int,  enum <anonymous> *)’} [-Werror=cast-function-type]
   written = ((Curl_send*)c->send_underlying)(conn, FIRSTSOCKET,
              ^
http2.c: In function ‘http2_recv’:
http2.c:1604:16: error: cast between incompatible function types from ‘recving’ {aka ‘int (*)(void)’} to ‘ssize_t (*)(struct connectdata *, int,  char *, size_t,  CURLcode *)’ {aka ‘long int (*)(struct connectdata *, int,  char *, long unsigned int,  enum <anonymous> *)’} [-Werror=cast-function-type]
       nread = ((Curl_recv *)httpc->recv_underlying)(
                ^
http2.c: In function ‘Curl_http2_switched’:
http2.c:2141:28: error: cast between incompatible function types from ‘ssize_t (*)(struct connectdata *, int,  char *, size_t,  CURLcode *)’ {aka ‘long int (*)(struct connectdata *, int,  char *, long unsigned int,  enum <anonymous> *)’} to ‘int (*)(void)’ [-Werror=cast-function-type]
   httpc->recv_underlying = (recving)conn->recv[FIRSTSOCKET];
                            ^
http2.c:2142:28: error: cast between incompatible function types from ‘ssize_t (*)(struct connectdata *, int,  const void *, size_t,  CURLcode *)’ {aka ‘long int (*)(struct connectdata *, int,  const void *, long unsigned int,  enum <anonymous> *)’} to ‘int (*)(void)’ [-Werror=cast-function-type]
   httpc->send_underlying = (sending)conn->send[FIRSTSOCKET];
                            ^
cc1: all warnings being treated as errors
make[2]: *** [Makefile:2874: libcurlu_la-http2.lo] Error 1
make[1]: *** [Makefile:746: all] Error 2
make: *** [Makefile:924: all-recursive] Error 1

This seems to be a new warning in Gcc 8 (https://gcc.gnu.org/gcc-8/changes.html)

-Wcast-function-type warns when a function pointer is cast to an incompatible function pointer. This warning is enabled by -Wextra.

curl/libcurl version

$ git rev-parse HEAD
c3d7db4ecb2f8a0b22bd7cdf54ef10c119ebcc48

operating system

Linux (Arch Linux)

[bagder]

I believe they're all fixed now. Can you confirm?

[rikardfalkeborn]

I can confirm no warnings.

[bagder]

Thanks @rikardfalkeborn! Case closed.