re: re build failure - hmac.c:74:31: error: invalid application of 'sizeof' to an incomplete type 'HMAC_CTX'

Hi,

Getting build failure with re. The file being referenced is ~5 years old.

  CC      build-i586/hmac/openssl/hmac.o
src/hmac/openssl/hmac.c:30:3: warning: implicit declaration of function 'HMAC_CTX_cleanup' is invalid in C99 [-Wimplicit-function-declaration]
                HMAC_CTX_cleanup(hmac->ctx);
                ^
src/hmac/openssl/hmac.c:74:31: error: invalid application of 'sizeof' to an incomplete type 'HMAC_CTX' (aka 'struct hmac_ctx_st')
        hmac->ctx = mem_zalloc(sizeof(*hmac->ctx), NULL);
                                     ^~~~~~~~~~~~
/usr/include/openssl/ossl_typ.h:114:16: note: forward declaration of 'struct hmac_ctx_st'
typedef struct hmac_ctx_st HMAC_CTX;
               ^
src/hmac/openssl/hmac.c:80:2: warning: implicit declaration of function 'HMAC_CTX_init' is invalid in C99 [-Wimplicit-function-declaration]
        HMAC_CTX_init(hmac->ctx);
        ^
2 warnings and 1 error generated.
gmake: *** [Makefile:122: build-i586/hmac/openssl/hmac.o] Error 1