Use #error in openssl/srp.h

Follow the same convention the other OPENSSL_NO_xxx header files
do, and use #error instead of making the header file be a no-op.

Reviewed-by: Matt Caswell <matt@openssl.org>

apps/s_client.c

@@ -925,6 +925,13 @@ int s_client_main(int argc, char **argv)
             srp_arg.amp = 1;
             meth = TLSv1_client_method();
             break;
+#else
+        case OPT_SRPUSER:
+        case OPT_SRPPASS:
+        case OPT_SRP_STRENGTH:
+        case OPT_SRP_LATEUSER:
+        case OPT_SRP_MOREGROUPS:
+            break;
 #endif
 #ifndef OPENSSL_NO_SSL3
         case OPT_SSL3:

apps/s_server.c

@@ -1317,6 +1317,10 @@ int s_server_main(int argc, char *argv[])
             srpuserseed = opt_arg();
             meth = TLSv1_server_method();
             break;
+#else
+        case OPT_SRPVFILE:
+        case OPT_SRPUSERSEED:
+            break;
 #endif
         case OPT_REV:
             rev = 1;

apps/srp.c

@@ -680,4 +680,10 @@ int srp_main(int argc, char **argv)
     return (ret);
 }
 
+#else
+
+# if PEDANTIC
+static void *dummy = &dummy;
+# endif
+
 #endif

include/openssl/srp.h

@@ -60,7 +60,11 @@
 #ifndef __SRP_H__
 # define __SRP_H__
 
-# ifndef OPENSSL_NO_SRP
+#include <openssl/opensslconf.h>
+
+# ifdef OPENSSL_NO_SRP
+#  error SRP is disabled.
+# endif
 
 # include <stdio.h>
 # include <string.h>
@@ -167,4 +171,3 @@ int SRP_Verify_B_mod_N(BIGNUM *B, BIGNUM *N);
 #endif
 
 #endif
-#endif

ssl/tls_srp.c

@@ -60,11 +60,11 @@
 
 #include <openssl/crypto.h>
 #include <openssl/rand.h>
-#include <openssl/srp.h>
 #include <openssl/err.h>
 #include "ssl_locl.h"
 
 #ifndef OPENSSL_NO_SRP
+#include <openssl/srp.h>
 
 int SSL_CTX_SRP_CTX_free(struct ssl_ctx_st *ctx)
 {