Merge bitcoin-core/secp256k1#1121: config: Set preprocessor defaults for ECMULT_* config values

c27ae45144 config: Remove basic-config.h (Tim Ruffing)
da6514a04a config: Introduce DEBUG_CONFIG macro for debug output of config (Tim Ruffing)
d0cf55e13a config: Set preprocessor defaults for ECMULT_* config values (Tim Ruffing)

Pull request description:

ACKs for top commit:
  sipa:
    ACK c27ae45144
  hebasto:
    ACK c27ae45144, I have reviewed the code and it looks correct.
  jonasnick:
    ACK c27ae45144

Tree-SHA512: 56b0f384bd9f42cf7c903bec08f4807db1415ddf9a06676dfe1e638e4d02431c522ef0422585e85429074e0dbb51da4f400cf53e8f883d6e07122731c57be1e3

Makefile.am

@@ -58,7 +58,6 @@ noinst_HEADERS += src/hash_impl.h
 noinst_HEADERS += src/field.h
 noinst_HEADERS += src/field_impl.h
 noinst_HEADERS += src/bench.h
-noinst_HEADERS += src/basic-config.h
 noinst_HEADERS += contrib/lax_der_parsing.h
 noinst_HEADERS += contrib/lax_der_parsing.c
 noinst_HEADERS += contrib/lax_der_privatekey_parsing.h

src/basic-config.h

@@ -1,17 +0,0 @@
-/***********************************************************************
- * Copyright (c) 2013, 2014 Pieter Wuille                              *
- * Distributed under the MIT software license, see the accompanying    *
- * file COPYING or https://www.opensource.org/licenses/mit-license.php.*
- ***********************************************************************/
-
-#ifndef SECP256K1_BASIC_CONFIG_H
-#define SECP256K1_BASIC_CONFIG_H
-
-#ifdef USE_BASIC_CONFIG
-
-#define ECMULT_WINDOW_SIZE 15
-#define ECMULT_GEN_PREC_BITS 4
-
-#endif /* USE_BASIC_CONFIG */
-
-#endif /* SECP256K1_BASIC_CONFIG_H */

src/ecmult.h

@@ -11,6 +11,17 @@
 #include "scalar.h"
 #include "scratch.h"
 
+#ifndef ECMULT_WINDOW_SIZE
+#  define ECMULT_WINDOW_SIZE 15
+#  ifdef DEBUG_CONFIG
+#     pragma message DEBUG_CONFIG_MSG("ECMULT_WINDOW_SIZE undefined, assuming default value")
+#  endif
+#endif
+
+#ifdef DEBUG_CONFIG
+#  pragma message DEBUG_CONFIG_DEF(ECMULT_WINDOW_SIZE)
+#endif
+
 /* Noone will ever need more than a window size of 24. The code might
  * be correct for larger values of ECMULT_WINDOW_SIZE but this is not
  * tested.

src/ecmult_gen.h

@@ -10,9 +10,21 @@
 #include "scalar.h"
 #include "group.h"
 
+#ifndef ECMULT_GEN_PREC_BITS
+#  define ECMULT_GEN_PREC_BITS 4
+#  ifdef DEBUG_CONFIG
+#     pragma message DEBUG_CONFIG_MSG("ECMULT_GEN_PREC_BITS undefined, assuming default value")
+#  endif
+#endif
+
+#ifdef DEBUG_CONFIG
+#  pragma message DEBUG_CONFIG_DEF(ECMULT_GEN_PREC_BITS)
+#endif
+
 #if ECMULT_GEN_PREC_BITS != 2 && ECMULT_GEN_PREC_BITS != 4 && ECMULT_GEN_PREC_BITS != 8
 #  error "Set ECMULT_GEN_PREC_BITS to 2, 4 or 8."
 #endif
+
 #define ECMULT_GEN_PREC_G(bits) (1 << bits)
 #define ECMULT_GEN_PREC_N(bits) (256 / bits)
 

src/util.h

@@ -16,6 +16,11 @@
 #include <stdio.h>
 #include <limits.h>
 
+#define STR_(x) #x
+#define STR(x) STR_(x)
+#define DEBUG_CONFIG_MSG(x) "DEBUG_CONFIG: " x
+#define DEBUG_CONFIG_DEF(x) DEBUG_CONFIG_MSG(#x "=" STR(x))
+
 typedef struct {
     void (*fn)(const char *text, void* data);
     const void* data;