diff --git a/include/secp256k1.h b/include/secp256k1.h
index 4a468e0..932bf02 100644
--- a/include/secp256k1.h
+++ b/include/secp256k1.h
@@ -1,13 +1,61 @@
 #ifndef _SECP256K1_
-#define _SECP256K1_
+# define _SECP256K1_
 
-#ifdef __cplusplus
+# ifdef __cplusplus
 extern "C" {
-#endif
+# endif
+
+# if !defined(SECP256K1_GNUC_PREREQ)
+#  if defined(__GNUC__)&&defined(__GNUC_MINOR__)
+#   define SECP256K1_GNUC_PREREQ(_maj,_min) \
+ ((__GNUC__<<16)+__GNUC_MINOR__>=((_maj)<<16)+(_min))
+#  else
+#   define SECP256K1_GNUC_PREREQ(_maj,_min) 0
+#  endif
+# endif
+
+# if (!defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L) )
+#  if SECP256K1_GNUC_PREREQ(3,0)
+#   define SECP256K1_RESTRICT __restrict__
+#  elif (defined(_MSC_VER) && _MSC_VER >= 1400)
+#   define SECP256K1_RESTRICT __restrict
+#  else
+#   define SECP256K1_RESTRICT
+#  endif
+# else
+#  define SECP256K1_RESTRICT restrict
+# endif
+
+# if (!defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L) )
+#  if SECP256K1_GNUC_PREREQ(2,7)
+#   define SECP256K1_INLINE __inline__
+#  elif (defined(_MSC_VER))
+#   define SECP256K1_INLINE __inline
+#  else
+#   define SECP256K1_INLINE
+#  endif
+# else
+#  define SECP256K1_INLINE inline
+# endif
+
+/**Warning attributes
+  * NONNULL is not used if SECP256K1_BUILD is set to avoid the compiler optimizing out
+  * some paranoid null checks. */
+# if defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4)
+#  define SECP256K1_WARN_UNUSED_RESULT __attribute__ ((__warn_unused_result__))
+# else
+#  define SECP256K1_WARN_UNUSED_RESULT
+# endif
+# if !defined(SECP256K1_BUILD) && defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4)
+#  define SECP256K1_ARG_NONNULL(_x)  __attribute__ ((__nonnull__(_x)))
+# else
+#  define SECP256K1_ARG_NONNULL(_x)
+# endif
+
 
 /** Flags to pass to secp256k1_start. */
-#define SECP256K1_START_VERIFY (1 << 0)
-#define SECP256K1_START_SIGN   (1 << 1)
+# define SECP256K1_START_VERIFY (1 << 0)
+# define SECP256K1_START_SIGN   (1 << 1)
 
 /** Initialize the library. This may take some time (10-100 ms).
  *  You need to call this before calling any other function.
@@ -34,9 +82,14 @@ void secp256k1_stop(void);
  *           pubkeylen: the length of pubkey
  * Requires starting using SECP256K1_START_VERIFY.
  */
-int secp256k1_ecdsa_verify(const unsigned char *msg, int msglen,
-                           const unsigned char *sig, int siglen,
-                           const unsigned char *pubkey, int pubkeylen);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_verify(
+  const unsigned char *msg,
+  int msglen,
+  const unsigned char *sig,
+  int siglen,
+  const unsigned char *pubkey,
+  int pubkeylen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5);
 
 /** Create an ECDSA signature.
  *  Returns: 1: signature created
@@ -50,10 +103,14 @@ int secp256k1_ecdsa_verify(const unsigned char *msg, int msglen,
  *                   to contain the actual signature length (<=72).
  * Requires starting using SECP256K1_START_SIGN.
  */
-int secp256k1_ecdsa_sign(const unsigned char *msg, int msglen,
-                         unsigned char *sig, int *siglen,
-                         const unsigned char *seckey,
-                         const unsigned char *nonce);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_sign(
+  const unsigned char *msg,
+  int msglen,
+  unsigned char *sig,
+  int *siglen,
+  const unsigned char *seckey,
+  const unsigned char *nonce
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(6);
 
 /** Create a compact ECDSA signature (64 byte + recovery id).
  *  Returns: 1: signature created
@@ -66,11 +123,14 @@ int secp256k1_ecdsa_sign(const unsigned char *msg, int msglen,
  *           recid:  pointer to an int, which will be updated to contain the recovery id (can be NULL)
  * Requires starting using SECP256K1_START_SIGN.
  */
-int secp256k1_ecdsa_sign_compact(const unsigned char *msg, int msglen,
-                                 unsigned char *sig64,
-                                 const unsigned char *seckey,
-                                 const unsigned char *nonce,
-                                 int *recid);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_sign_compact(
+  const unsigned char *msg,
+  int msglen,
+  unsigned char *sig64,
+  const unsigned char *seckey,
+  const unsigned char *nonce,
+  int *recid
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
 
 /** Recover an ECDSA public key from a compact signature.
  *  Returns: 1: public key successfully recovered (which guarantees a correct signature).
@@ -84,17 +144,22 @@ int secp256k1_ecdsa_sign_compact(const unsigned char *msg, int msglen,
  *           pubkeylen:  pointer to an int that will contain the pubkey length (cannot be NULL)
  * Requires starting using SECP256K1_START_VERIFY.
  */
-int secp256k1_ecdsa_recover_compact(const unsigned char *msg, int msglen,
-                                    const unsigned char *sig64,
-                                    unsigned char *pubkey, int *pubkeylen,
-                                    int compressed, int recid);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_recover_compact(
+  const unsigned char *msg,
+  int msglen,
+  const unsigned char *sig64,
+  unsigned char *pubkey,
+  int *pubkeylen,
+  int compressed,
+  int recid
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
 
 /** Verify an ECDSA secret key.
  *  Returns: 1: secret key is valid
  *           0: secret key is invalid
  *  In:      seckey: pointer to a 32-byte secret key (cannot be NULL)
  */
-int secp256k1_ec_seckey_verify(const unsigned char *seckey);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_verify(const unsigned char *seckey) SECP256K1_ARG_NONNULL(1);
 
 /** Just validate a public key.
  *  Returns: 1: valid public key
@@ -102,7 +167,7 @@ int secp256k1_ec_seckey_verify(const unsigned char *seckey);
  *  In:      pubkey:    pointer to a 33-byte or 65-byte public key (cannot be NULL).
  *           pubkeylen: length of pubkey
  */
-int secp256k1_ec_pubkey_verify(const unsigned char *pubkey, int pubkeylen);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_verify(const unsigned char *pubkey, int pubkeylen) SECP256K1_ARG_NONNULL(1);
 
 /** Compute the public key for a secret key.
  *  In:     compressed: whether the computed public key should be compressed
@@ -115,7 +180,12 @@ int secp256k1_ec_pubkey_verify(const unsigned char *pubkey, int pubkeylen);
  *           0: secret was invalid, try again.
  * Requires starting using SECP256K1_START_SIGN.
  */
-int secp256k1_ec_pubkey_create(unsigned char *pubkey, int *pubkeylen, const unsigned char *seckey, int compressed);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create(
+  unsigned char *pubkey,
+  int *pubkeylen,
+  const unsigned char *seckey,
+  int compressed
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 /** Decompress a public key.
  * In/Out: pubkey:    pointer to a 65-byte array to put the decompressed public key.
@@ -125,35 +195,58 @@ int secp256k1_ec_pubkey_create(unsigned char *pubkey, int *pubkeylen, const unsi
  * Returns: 0 if the passed public key was invalid, 1 otherwise. If 1 is returned, the
             pubkey is replaced with its decompressed version.
  */
-int secp256k1_ec_pubkey_decompress(unsigned char *pubkey, int *pubkeylen);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_decompress(
+  unsigned char *pubkey,
+  int *pubkeylen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
 
 /** Export a private key in DER format. */
-int secp256k1_ec_privkey_export(const unsigned char *seckey,
-                                unsigned char *privkey, int *privkeylen,
-                                int compressed);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_export(
+  const unsigned char *seckey,
+  unsigned char *privkey,
+  int *privkeylen,
+  int compressed
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 /** Import a private key in DER format. */
-int secp256k1_ec_privkey_import(unsigned char *seckey,
-                                const unsigned char *privkey, int privkeylen);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_import(
+  unsigned char *seckey,
+  const unsigned char *privkey,
+  int privkeylen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
 
 /** Tweak a private key by adding tweak to it. */
-int secp256k1_ec_privkey_tweak_add(unsigned char *seckey, const unsigned char *tweak);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_add(
+  unsigned char *seckey,
+  const unsigned char *tweak
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
 
 /** Tweak a public key by adding tweak times the generator to it.
  * Requires starting with SECP256K1_START_VERIFY.
  */
-int secp256k1_ec_pubkey_tweak_add(unsigned char *pubkey, int pubkeylen, const unsigned char *tweak);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add(
+  unsigned char *pubkey,
+  int pubkeylen,
+  const unsigned char *tweak
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3);
 
 /** Tweak a private key by multiplying it with tweak. */
-int secp256k1_ec_privkey_tweak_mul(unsigned char *seckey, const unsigned char *tweak);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul(
+  unsigned char *seckey,
+  const unsigned char *tweak
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
 
 /** Tweak a public key by multiplying it with tweak.
  * Requires starting with SECP256K1_START_VERIFY.
  */
-int secp256k1_ec_pubkey_tweak_mul(unsigned char *pubkey, int pubkeylen, const unsigned char *tweak);
+SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul(
+  unsigned char *pubkey,
+  int pubkeylen,
+  const unsigned char *tweak
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3);
 
-#ifdef __cplusplus
+# ifdef __cplusplus
 }
-#endif
+# endif
 
 #endif
diff --git a/src/ecmult_gen_impl.h b/src/ecmult_gen_impl.h
index 3b568ab..63c402b 100644
--- a/src/ecmult_gen_impl.h
+++ b/src/ecmult_gen_impl.h
@@ -5,7 +5,6 @@
 #ifndef _SECP256K1_ECMULT_GEN_IMPL_H_
 #define _SECP256K1_ECMULT_GEN_IMPL_H_
 
-#include <assert.h>
 #include "scalar.h"
 #include "group.h"
 #include "ecmult_gen.h"
diff --git a/src/ecmult_impl.h b/src/ecmult_impl.h
index c0e4b11..3757974 100644
--- a/src/ecmult_impl.h
+++ b/src/ecmult_impl.h
@@ -5,7 +5,6 @@
 #ifndef _SECP256K1_ECMULT_IMPL_H_
 #define _SECP256K1_ECMULT_IMPL_H_
 
-#include <assert.h>
 #include "num.h"
 #include "group.h"
 #include "ecmult.h"
diff --git a/src/field_10x26_impl.h b/src/field_10x26_impl.h
index a567437..c082f24 100644
--- a/src/field_10x26_impl.h
+++ b/src/field_10x26_impl.h
@@ -6,7 +6,6 @@
 #define _SECP256K1_FIELD_REPR_IMPL_H_
 
 #include <stdio.h>
-#include <assert.h>
 #include <string.h>
 #include "util.h"
 #include "num.h"
diff --git a/src/field_5x52_impl.h b/src/field_5x52_impl.h
index 5afabae..c527714 100644
--- a/src/field_5x52_impl.h
+++ b/src/field_5x52_impl.h
@@ -9,7 +9,6 @@
 #include "libsecp256k1-config.h"
 #endif
 
-#include <assert.h>
 #include <string.h>
 #include "util.h"
 #include "num.h"
diff --git a/src/num_gmp_impl.h b/src/num_gmp_impl.h
index d8442ee..e91f543 100644
--- a/src/num_gmp_impl.h
+++ b/src/num_gmp_impl.h
@@ -5,7 +5,6 @@
 #ifndef _SECP256K1_NUM_REPR_IMPL_H_
 #define _SECP256K1_NUM_REPR_IMPL_H_
 
-#include <assert.h>
 #include <string.h>
 #include <stdlib.h>
 #include <gmp.h>
diff --git a/src/secp256k1.c b/src/secp256k1.c
index 3e37648..f017342 100644
--- a/src/secp256k1.c
+++ b/src/secp256k1.c
@@ -2,9 +2,10 @@
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#define SECP256K1_BUILD (1)
+
 #include "include/secp256k1.h"
 
-#include <assert.h>
 #include "util.h"
 #include "num_impl.h"
 #include "field_impl.h"