build: add some build options to customise library functionality

core/mt19937.c

@@ -217,6 +217,7 @@ static uint64_t genrand64_int64(struct fx_random_ctx *context)
 #endif
 }
 
+#if FX_ENABLE_FLOATING_POINT == 1
 /* generates a random number on [0,1]-real-interval */
 double genrand64_real1(struct fx_random_ctx *context)
 {
@@ -235,6 +236,7 @@ double genrand64_real3(struct fx_random_ctx *context)
 	return ((genrand64_int64(context) >> 12) + 0.5)
 	     * (1.0 / 4503599627370496.0);
 }
+#endif
 
 struct fx_random_algorithm z__fx_gen_mt19937 = {
 	.gen_name = "mt19937",

core/printf.c

@@ -45,6 +45,11 @@
 
 #include "printf.h"
 
+#if FX_ENABLE_FLOATING_POINT == 0
+#define PRINTF_SUPPORT_DECIMAL_SPECIFIERS     0
+#define PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS 0
+#endif
+
 #ifdef __cplusplus
 #include <climits>
 #include <cstdint>

core/random.c

@@ -60,6 +60,7 @@ unsigned long long fx_random_next_int64(struct fx_random_ctx *ctx)
 	return ctx->__a->gen_getrand(ctx);
 }
 
+#if FX_ENABLE_FLOATING_POINT
 double fx_random_next_double(struct fx_random_ctx *ctx)
 {
 	unsigned long long v = fx_random_next_int64(ctx);
@@ -69,8 +70,10 @@ double fx_random_next_double(struct fx_random_ctx *ctx)
 
 	return (double)(v >> 11) * (1.0 / 9007199254740991.0);
 }
+#endif
 
-void fx_random_next_bytes(struct fx_random_ctx *ctx, unsigned char *out, size_t nbytes)
+void fx_random_next_bytes(
+	struct fx_random_ctx *ctx, unsigned char *out, size_t nbytes)
 {
 	size_t n_qwords = 0;
 	n_qwords = nbytes >> 3;