Remove #error from include files.

Don't have #error statements in header files, but instead wrap
the contents of that file in #ifndef OPENSSL_NO_xxx
This means it is now always safe to include the header file.

Reviewed-by: Richard Levitte <levitte@openssl.org>

31 files changed, 216 insertions, 308 deletions

diff --git a/include/openssl/aes.h b/include/openssl/aes.h
index 8c36a4d64f..f81ec0dc51 100644
--- a/include/openssl/aes.h
+++ b/include/openssl/aes.h
@@ -53,11 +53,11 @@
 
 # include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_AES
-#  error AES is disabled.
-# endif
-
+#ifndef OPENSSL_NO_AES
 # include <stddef.h>
+# ifdef  __cplusplus
+extern "C" {
+# endif
 
 # define AES_ENCRYPT     1
 # define AES_DECRYPT     0
@@ -69,10 +69,6 @@
 # define AES_MAXNR 14
 # define AES_BLOCK_SIZE 16
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 /* This should be a hidden type, but EVP requires that the size be known */
 struct aes_key_st {
 # ifdef AES_LONG
@@ -131,8 +127,9 @@ int AES_unwrap_key(AES_KEY *key, const unsigned char *iv,
                    const unsigned char *in, unsigned int inlen);
 
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
-#endif                          /* !HEADER_AES_H */
+#endif
diff --git a/include/openssl/blowfish.h b/include/openssl/blowfish.h
index ee4afa542d..5e0af533cf 100644
--- a/include/openssl/blowfish.h
+++ b/include/openssl/blowfish.h
@@ -58,14 +58,12 @@
 #ifndef HEADER_BLOWFISH_H
 # define HEADER_BLOWFISH_H
 
-# include <openssl/e_os2.h>
+# include <openssl/opensslconf.h>
 
-#ifdef  __cplusplus
+# ifndef OPENSSL_NO_BF
+# include <openssl/e_os2.h>
+# ifdef  __cplusplus
 extern "C" {
-#endif
-
-# ifdef OPENSSL_NO_BF
-#  error BF is disabled.
 # endif
 
 # define BF_ENCRYPT      1
@@ -103,8 +101,9 @@ void BF_ofb64_encrypt(const unsigned char *in, unsigned char *out,
                       unsigned char *ivec, int *num);
 const char *BF_options(void);
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/bn.h b/include/openssl/bn.h
index 8d2d5a8be0..315b99e748 100644
--- a/include/openssl/bn.h
+++ b/include/openssl/bn.h
@@ -126,7 +126,7 @@
 
 # include <openssl/e_os2.h>
 # ifndef OPENSSL_NO_STDIO
-#  include <stdio.h>            /* FILE */
+#  include <stdio.h>
 # endif
 # include <openssl/opensslconf.h>
 # include <openssl/ossl_typ.h>
diff --git a/include/openssl/camellia.h b/include/openssl/camellia.h
index d04d2a8b3a..d05b392549 100644
--- a/include/openssl/camellia.h
+++ b/include/openssl/camellia.h
@@ -53,11 +53,11 @@
 
 # include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_CAMELLIA
-#  error CAMELLIA is disabled.
-# endif
-
+# ifndef OPENSSL_NO_CAMELLIA
 # include <stddef.h>
+#ifdef  __cplusplus
+extern "C" {
+#endif
 
 # define CAMELLIA_ENCRYPT        1
 # define CAMELLIA_DECRYPT        0
@@ -67,10 +67,6 @@
  * Both sizes are in bytes.
  */
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 /* This should be a hidden type, but EVP requires that the size be known */
 
 # define CAMELLIA_BLOCK_SIZE 16
@@ -120,8 +116,9 @@ void Camellia_ctr128_encrypt(const unsigned char *in, unsigned char *out,
                              unsigned char ecount_buf[CAMELLIA_BLOCK_SIZE],
                              unsigned int *num);
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
-#endif                          /* !HEADER_Camellia_H */
+#endif
diff --git a/include/openssl/cast.h b/include/openssl/cast.h
index 87d1933a9b..c54d3c9219 100644
--- a/include/openssl/cast.h
+++ b/include/openssl/cast.h
@@ -58,14 +58,11 @@
 #ifndef HEADER_CAST_H
 # define HEADER_CAST_H
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 # include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_CAST
-#  error CAST is disabled.
+# ifndef OPENSSL_NO_CAST
+# ifdef  __cplusplus
+extern "C" {
 # endif
 
 # define CAST_ENCRYPT    1
@@ -96,8 +93,9 @@ void CAST_ofb64_encrypt(const unsigned char *in, unsigned char *out,
                         long length, const CAST_KEY *schedule,
                         unsigned char *ivec, int *num);
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/cms.h b/include/openssl/cms.h
index f8d55d84d2..5ae701e585 100644
--- a/include/openssl/cms.h
+++ b/include/openssl/cms.h
@@ -54,16 +54,14 @@
 #ifndef HEADER_CMS_H
 # define HEADER_CMS_H
 
+# include <openssl/opensslconf.h>
+
+# ifndef OPENSSL_NO_CMS
 # include <openssl/x509.h>
 # include <openssl/x509v3.h>
-
-# ifdef OPENSSL_NO_CMS
-#  error CMS is disabled.
-# endif
-
-#ifdef __cplusplus
+# ifdef __cplusplus
 extern "C" {
-#endif
+# endif
 
 typedef struct CMS_ContentInfo_st CMS_ContentInfo;
 typedef struct CMS_SignerInfo_st CMS_SignerInfo;
@@ -551,7 +549,9 @@ void ERR_load_CMS_strings(void);
 # define CMS_R_VERIFICATION_FAILURE                       158
 # define CMS_R_WRAP_ERROR                                 159
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
+
 #endif
diff --git a/include/openssl/comp.h b/include/openssl/comp.h
index de16a9fcdb..de4eb32561 100644
--- a/include/openssl/comp.h
+++ b/include/openssl/comp.h
@@ -56,15 +56,14 @@
 #ifndef HEADER_COMP_H
 # define HEADER_COMP_H
 
-# include <openssl/crypto.h>
+# include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_COMP
-#  error COMP is disabled.
+# ifndef OPENSSL_NO_COMP
+# include <openssl/crypto.h>
+# ifdef  __cplusplus
+extern "C" {
 # endif
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
 
 
 COMP_CTX *COMP_CTX_new(COMP_METHOD *meth);
@@ -110,5 +109,7 @@ void ERR_load_COMP_strings(void);
 
 #ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
+
 #endif
diff --git a/include/openssl/ct.h b/include/openssl/ct.h
index f148a270aa..0da3125d17 100644
--- a/include/openssl/ct.h
+++ b/include/openssl/ct.h
@@ -51,21 +51,20 @@
 * ====================================================================
 */
 
-#ifdef OPENSSL_NO_CT
-# error "CT is disabled"
-#endif
-
 #ifndef HEADER_CT_H
 # define HEADER_CT_H
 
+# include <openssl/opensslconf.h>
+
+# ifndef OPENSSL_NO_CT
 # include <openssl/ossl_typ.h>
 # include <openssl/safestack.h>
 # include <openssl/x509.h>
-
 # ifdef  __cplusplus
 extern "C" {
 # endif
 
+
 /* Minimum RSA key size, from RFC6962 */
 # define SCT_MIN_RSA_BITS 2048
 
@@ -601,7 +600,9 @@ void ERR_load_CT_strings(void);
 # define CT_R_UNSUPPORTED_ENTRY_TYPE                      102
 # define CT_R_UNSUPPORTED_VERSION                         103
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
+
 #endif
diff --git a/include/openssl/des.h b/include/openssl/des.h
index 13ce232703..633d070b39 100644
--- a/include/openssl/des.h
+++ b/include/openssl/des.h
@@ -55,14 +55,16 @@
  * [including the GNU Public Licence.]
  */
 
-#ifndef HEADER_NEW_DES_H
-# define HEADER_NEW_DES_H
+#ifndef HEADER_DES_H
+# define HEADER_DES_H
 
-# include <openssl/e_os2.h>
+# include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_DES
-#  error DES is disabled.
+# ifndef OPENSSL_NO_DES
+# ifdef  __cplusplus
+extern "C" {
 # endif
+# include <openssl/e_os2.h>
 
 typedef unsigned int DES_LONG;
 
@@ -71,10 +73,6 @@ typedef unsigned int DES_LONG;
 #  define OPENSSL_EXTERN OPENSSL_EXPORT
 # endif
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 typedef unsigned char DES_cblock[8];
 typedef /* const */ unsigned char const_DES_cblock[8];
 /*
@@ -228,8 +226,9 @@ int DES_read_2passwords(DES_cblock *key1, DES_cblock *key2,
 
 # define DES_fixup_key_parity DES_set_odd_parity
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/dh.h b/include/openssl/dh.h
index e852cbe446..2e021e235b 100644
--- a/include/openssl/dh.h
+++ b/include/openssl/dh.h
@@ -58,13 +58,10 @@
 #ifndef HEADER_DH_H
 # define HEADER_DH_H
 
-# include <openssl/e_os2.h>
 # include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_DH
-#  error DH is disabled.
-# endif
-
+# ifndef OPENSSL_NO_DH
+# include <openssl/e_os2.h>
 # include <openssl/bio.h>
 # include <openssl/asn1.h>
 # include <openssl/ossl_typ.h>
@@ -72,6 +69,10 @@
 #  include <openssl/bn.h>
 # endif
 
+# ifdef  __cplusplus
+extern "C" {
+# endif
+
 # ifndef OPENSSL_DH_MAX_MODULUS_BITS
 #  define OPENSSL_DH_MAX_MODULUS_BITS    10000
 # endif
@@ -79,15 +80,6 @@
 # define OPENSSL_DH_FIPS_MIN_MODULUS_BITS 1024
 
 # define DH_FLAG_CACHE_MONT_P     0x01
-
-/*
- * new with 0.9.7h; the built-in DH
- * implementation now uses constant time
- * modular exponentiation for secret exponents
- * by default. This flag causes the
- * faster variable sliding window method to
- * be used for all exponents.
- */
 # define DH_FLAG_NO_EXP_CONSTTIME 0x02
 
 /*
@@ -107,10 +99,6 @@
 
 # define DH_FLAG_NON_FIPS_ALLOW                  0x0400
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 /* Already defined in ossl_typ.h */
 /* typedef struct dh_st DH; */
 /* typedef struct dh_method DH_METHOD; */
@@ -389,7 +377,9 @@ void ERR_load_DH_strings(void);
 # define DH_R_PEER_KEY_ERROR                              111
 # define DH_R_SHARED_INFO_ERROR                           113
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
+
 #endif
diff --git a/include/openssl/dsa.h b/include/openssl/dsa.h
index 865344932f..240a1afa84 100644
--- a/include/openssl/dsa.h
+++ b/include/openssl/dsa.h
@@ -63,22 +63,20 @@
 #ifndef HEADER_DSA_H
 # define HEADER_DSA_H
 
-# include <openssl/e_os2.h>
+# include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_DSA
-#  error DSA is disabled.
+# ifndef OPENSSL_NO_DSA
+# ifdef  __cplusplus
+extern "C" {
 # endif
-
+# include <openssl/e_os2.h>
 # include <openssl/bio.h>
 # include <openssl/crypto.h>
 # include <openssl/ossl_typ.h>
 # include <openssl/opensslconf.h>
-
 # if OPENSSL_API_COMPAT < 0x10100000L
 #  include <openssl/bn.h>
-#  ifndef OPENSSL_NO_DH
-#   include <openssl/dh.h>
-#  endif
+#  include <openssl/dh.h>
 # endif
 
 # ifndef OPENSSL_DSA_MAX_MODULUS_BITS
@@ -113,10 +111,6 @@
 # define DSA_FLAG_NON_FIPS_ALLOW                 0x0400
 # define DSA_FLAG_FIPS_CHECKED                   0x0800
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 /* Already defined in ossl_typ.h */
 /* typedef struct dsa_st DSA; */
 /* typedef struct dsa_method DSA_METHOD; */
@@ -323,7 +317,9 @@ void ERR_load_DSA_strings(void);
 # define DSA_R_PARAMETER_ENCODING_ERROR                   105
 # define DSA_R_Q_NOT_PRIME                                113
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
+
 #endif
diff --git a/include/openssl/ec.h b/include/openssl/ec.h
index 103f718208..892239dd87 100644
--- a/include/openssl/ec.h
+++ b/include/openssl/ec.h
@@ -1,12 +1,6 @@
-
-/* crypto/ec/ec.h */
 /*
  * Originally written by Bodo Moeller for the OpenSSL project.
  */
-/**
- * \file crypto/ec/ec.h Include file for the OpenSSL EC functions
- * \author Originally written by Bodo Moeller for the OpenSSL project
- */
 /* ====================================================================
  * Copyright (c) 1998-2005 The OpenSSL Project.  All rights reserved.
  *
@@ -79,22 +73,14 @@
 
 # include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_EC
-#  error EC is disabled.
-# endif
-
+# ifndef OPENSSL_NO_EC
 # include <openssl/asn1.h>
 # include <openssl/symhacks.h>
 # if OPENSSL_API_COMPAT < 0x10100000L
 #  include <openssl/bn.h>
 # endif
-
 # ifdef  __cplusplus
 extern "C" {
-# elif defined(__SUNPRO_C)
-#  if __SUNPRO_C >= 0x520
-#   pragma error_messages (off,E_ARRAY_OF_INCOMPLETE_NONAME,E_ARRAY_OF_INCOMPLETE)
-#  endif
 # endif
 
 # ifndef OPENSSL_ECC_MAX_FIELD_BITS
@@ -1650,7 +1636,9 @@ void ERR_load_EC_strings(void);
 # define EC_R_WRONG_CURVE_PARAMETERS                      145
 # define EC_R_WRONG_ORDER                                 130
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
+
 #endif
diff --git a/include/openssl/engine.h b/include/openssl/engine.h
index d1cd17a24c..c12e02755f 100644
--- a/include/openssl/engine.h
+++ b/include/openssl/engine.h
@@ -66,37 +66,23 @@
 
 # include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_ENGINE
-#  error ENGINE is disabled.
-# endif
-
+# ifndef OPENSSL_NO_ENGINE
 # if OPENSSL_API_COMPAT < 0x10100000L
 #  include <openssl/bn.h>
-#  ifndef OPENSSL_NO_RSA
-#   include <openssl/rsa.h>
-#  endif
-#  ifndef OPENSSL_NO_DSA
-#   include <openssl/dsa.h>
-#  endif
-#  ifndef OPENSSL_NO_DH
-#   include <openssl/dh.h>
-#  endif
-#  ifndef OPENSSL_NO_EC
-#   include <openssl/ec.h>
-#  endif
+#  include <openssl/rsa.h>
+#  include <openssl/dsa.h>
+#  include <openssl/dh.h>
+#  include <openssl/ec.h>
 #  include <openssl/rand.h>
 #  include <openssl/ui.h>
 #  include <openssl/err.h>
 # endif
-
 # include <openssl/ossl_typ.h>
 # include <openssl/symhacks.h>
-
 # include <openssl/x509.h>
-
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 extern "C" {
-#endif
+# endif
 
 /*
  * These flags are used to control combinations of algorithm (methods) by
@@ -905,7 +891,9 @@ void ERR_load_ENGINE_strings(void);
 # define ENGINE_R_UNIMPLEMENTED_PUBLIC_KEY_METHOD         101
 # define ENGINE_R_VERSION_INCOMPATIBILITY                 145
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
+
 #endif
diff --git a/include/openssl/idea.h b/include/openssl/idea.h
index 29b5094394..165ee405ac 100644
--- a/include/openssl/idea.h
+++ b/include/openssl/idea.h
@@ -60,8 +60,9 @@
 
 # include <openssl/opensslconf.h>
 
-# ifdef OPENSSL_NO_IDEA
-#  error IDEA is disabled.
+# ifndef OPENSSL_NO_IDEA
+# ifdef  __cplusplus
+extern "C" {
 # endif
 
 typedef unsigned int IDEA_INT;
@@ -72,10 +73,6 @@ typedef unsigned int IDEA_INT;
 # define IDEA_BLOCK      8
 # define IDEA_KEY_LENGTH 16
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 typedef struct idea_key_st {
     IDEA_INT data[9][6];
 } IDEA_KEY_SCHEDULE;
@@ -95,8 +92,9 @@ void idea_ofb64_encrypt(const unsigned char *in, unsigned char *out,
                         long length, IDEA_KEY_SCHEDULE *ks, unsigned char *iv,
                         int *num);
 void idea_encrypt(unsigned long *in, IDEA_KEY_SCHEDULE *ks);
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/lhash.h b/include/openssl/lhash.h
index 899544ce04..2edd738a8b 100644
--- a/include/openssl/lhash.h
+++ b/include/openssl/lhash.h
@@ -63,10 +63,6 @@
 # define HEADER_LHASH_H
 
 # include <openssl/e_os2.h>
-# ifndef OPENSSL_NO_STDIO
-#  include <stdio.h>
-# endif
-
 # include <openssl/bio.h>
 
 #ifdef  __cplusplus
diff --git a/include/openssl/md2.h b/include/openssl/md2.h
index 1dba7cf395..d77a4fac9c 100644
--- a/include/openssl/md2.h
+++ b/include/openssl/md2.h
@@ -59,20 +59,18 @@
 # define HEADER_MD2_H
 
 # include <openssl/opensslconf.h>
-# ifdef OPENSSL_NO_MD2
-#  error MD2 is disabled.
-# endif
+
+# ifndef OPENSSL_NO_MD2
 # include <stddef.h>
+# ifdef  __cplusplus
+extern "C" {
+# endif
 
 typedef unsigned char MD2_INT;
 
 # define MD2_DIGEST_LENGTH       16
 # define MD2_BLOCK               16
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 typedef struct MD2state_st {
     unsigned int num;
     unsigned char data[MD2_BLOCK];
@@ -85,8 +83,10 @@ int MD2_Init(MD2_CTX *c);
 int MD2_Update(MD2_CTX *c, const unsigned char *data, size_t len);
 int MD2_Final(unsigned char *md, MD2_CTX *c);
 unsigned char *MD2(const unsigned char *d, size_t n, unsigned char *md);
-#ifdef  __cplusplus
+
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/md4.h b/include/openssl/md4.h
index c937625f93..b40a839128 100644
--- a/include/openssl/md4.h
+++ b/include/openssl/md4.h
@@ -58,15 +58,13 @@
 #ifndef HEADER_MD4_H
 # define HEADER_MD4_H
 
+# include <openssl/opensslconf.h>
+
+# ifndef OPENSSL_NO_MD4
 # include <openssl/e_os2.h>
 # include <stddef.h>
-
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 extern "C" {
-#endif
-
-# ifdef OPENSSL_NO_MD4
-#  error MD4 is disabled.
 # endif
 
 /*-
@@ -92,8 +90,10 @@ int MD4_Update(MD4_CTX *c, const void *data, size_t len);
 int MD4_Final(unsigned char *md, MD4_CTX *c);
 unsigned char *MD4(const unsigned char *d, size_t n, unsigned char *md);
 void MD4_Transform(MD4_CTX *c, const unsigned char *b);
-#ifdef  __cplusplus
+
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/md5.h b/include/openssl/md5.h
index 02ea76a54e..5b34b463e9 100644
--- a/include/openssl/md5.h
+++ b/include/openssl/md5.h
@@ -58,15 +58,13 @@
 #ifndef HEADER_MD5_H
 # define HEADER_MD5_H
 
+# include <openssl/opensslconf.h>
+
+# ifndef OPENSSL_NO_MD5
 # include <openssl/e_os2.h>
 # include <stddef.h>
-
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 extern "C" {
-#endif
-
-# ifdef OPENSSL_NO_MD5
-#  error MD5 is disabled.
 # endif
 
 /*
@@ -92,8 +90,9 @@ int MD5_Update(MD5_CTX *c, const void *data, size_t len);
 int MD5_Final(unsigned char *md, MD5_CTX *c);
 unsigned char *MD5(const unsigned char *d, size_t n, unsigned char *md);
 void MD5_Transform(MD5_CTX *c, const unsigned char *b);
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/mdc2.h b/include/openssl/mdc2.h
index fc9784fa18..229b122719 100644
--- a/include/openssl/mdc2.h
+++ b/include/openssl/mdc2.h
@@ -58,14 +58,12 @@
 #ifndef HEADER_MDC2_H
 # define HEADER_MDC2_H
 
-# include <openssl/des.h>
+# include <openssl/opensslconf.h>
 
-#ifdef  __cplusplus
+#ifndef OPENSSL_NO_MDC2
+# include <openssl/des.h>
+# ifdef  __cplusplus
 extern "C" {
-#endif
-
-# ifdef OPENSSL_NO_MDC2
-#  error MDC2 is disabled.
 # endif
 
 # define MDC2_BLOCK              8
@@ -83,8 +81,9 @@ int MDC2_Update(MDC2_CTX *c, const unsigned char *data, size_t len);
 int MDC2_Final(unsigned char *md, MDC2_CTX *c);
 unsigned char *MDC2(const unsigned char *d, size_t n, unsigned char *md);
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/rc2.h b/include/openssl/rc2.h
index 0bf6ae31ec..50be22dcec 100644
--- a/include/openssl/rc2.h
+++ b/include/openssl/rc2.h
@@ -59,8 +59,10 @@
 # define HEADER_RC2_H
 
 # include <openssl/opensslconf.h>
-# ifdef OPENSSL_NO_RC2
-#  error RC2 is disabled.
+
+# ifndef OPENSSL_NO_RC2
+# ifdef  __cplusplus
+extern "C" {
 # endif
 
 typedef unsigned int RC2_INT;
@@ -71,10 +73,6 @@ typedef unsigned int RC2_INT;
 # define RC2_BLOCK       8
 # define RC2_KEY_LENGTH  16
 
-#ifdef  __cplusplus
-extern "C" {
-#endif
-
 typedef struct rc2_key_st {
     RC2_INT data[64];
 } RC2_KEY;
@@ -93,8 +91,9 @@ void RC2_ofb64_encrypt(const unsigned char *in, unsigned char *out,
                        long length, RC2_KEY *schedule, unsigned char *ivec,
                        int *num);
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/rc4.h b/include/openssl/rc4.h
index c938fdb92a..a5fdbfb92c 100644
--- a/include/openssl/rc4.h
+++ b/include/openssl/rc4.h
@@ -58,13 +58,10 @@
 #ifndef HEADER_RC4_H
 # define HEADER_RC4_H
 
-# include <openssl/opensslconf.h>/* OPENSSL_NO_RC4, RC4_INT */
-# ifdef OPENSSL_NO_RC4
-#  error RC4 is disabled.
-# endif
+# include <openssl/opensslconf.h>
 
+# ifndef OPENSSL_NO_RC4
 # include <stddef.h>
-
 #ifdef  __cplusplus
 extern "C" {
 #endif
@@ -79,8 +76,9 @@ void RC4_set_key(RC4_KEY *key, int len, const unsigned char *data);
 void RC4(RC4_KEY *key, size_t len, const unsigned char *indata,
          unsigned char *outdata);
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif
 
 #endif
diff --git a/include/openssl/rc5.h b/include/openssl/rc5.h
index 026a1147a9..c1ff358ad3 100644
--- a/include/openssl/rc5.h
+++ b/include/openssl/rc5.h
@@ -58,14 +58,11 @@
 #ifndef HEADER_RC5_H
 # define HEADER_RC5_H
 
-# include <openssl/opensslconf.h>/* OPENSSL_NO_RC5 */
+# include <openssl/opensslconf.h>
 
-#ifdef  __cplusplus
+# ifndef OPENSSL_NO_RC5
+# ifdef  __cplusplus
 extern "C" {
-#endif
-
-# ifdef OPENSSL_NO_RC5
-#  error RC5 is disabled.
 # endif
 
 # define RC5_ENCRYPT     1
@@ -106,8 +103,9 @@ void RC5_32_ofb64_encrypt(const unsigned char *in, unsigned char *out,
                           long length, RC5_32_KEY *schedule,
                           unsigned char *ivec, int *num);
 
-#ifdef  __cplusplus
+# ifdef  __cplusplus
 }
-#endif
+# endif
+# endif