config: Introduce DEBUG_CONFIG macro for debug output of config

src/ecmult.h

@@ -13,7 +13,15 @@
 
 #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

@@ -12,10 +12,19 @@
 
 #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;