Disabling floating point code in mini-gmp?

[Niels Möller]

Hi,

in mini-gmp.c there's check #if !defined(MINI_GMP_DONT_USE_FLOAT_H), to
not include float.h, in which case we'll assume 53 mantissa bits. This
is set where mini-gmp.c is included in bootstrap.c. As far as I'm aware,
it's not used anywhere else.

I think I'd like to replace this with a knob to exclude all float
functions. I think we've discussed earlier if mini-gmp should be made
more modular; it might be nice to include mini-gmp.c and enable only the
functions that you need. Which may be a rabbit hole if we try to do it
thoroughly.

My motivation for disabling floats in particular is for supporting
embedded systems without floating point, where it's desirable to not get
a link dependency on a software float implementation. The hardware I'm
interested in at the moment is the tillitis tkey (an open hardware
device, which uses a 32-bit riscv with a multipler, but no divider and
no floats).

Proposed patch below. What do you think?

Regards,
/Niels

diff -r 1dc7d5dabc8d bootstrap.c
--- a/bootstrap.c	Fri Sep 19 17:18:39 2025 +0200
+++ b/bootstrap.c	Wed Sep 24 08:59:37 2025 +0200
@@ -29,7 +29,7 @@
 see https://www.gnu.org/licenses/.  */
 
 
-#define MINI_GMP_DONT_USE_FLOAT_H 1
+#define MINI_GMP_ENABLE_FLOAT 0
 #include "mini-gmp/mini-gmp.c"
 
 #define MIN(l,o) ((l) < (o) ? (l) : (o))
diff -r 1dc7d5dabc8d mini-gmp/mini-gmp.c
--- a/mini-gmp/mini-gmp.c	Fri Sep 19 17:18:39 2025 +0200
+++ b/mini-gmp/mini-gmp.c	Wed Sep 24 08:59:37 2025 +0200
@@ -51,7 +51,11 @@
 
 #include "mini-gmp.h"
 
-#if !defined(MINI_GMP_DONT_USE_FLOAT_H)
+#ifndef MINI_GMP_ENABLE_FLOAT
+#define MINI_GMP_ENABLE_FLOAT 1
+#endif
+
+#if MINI_GMP_ENABLE_FLOAT
 #include <float.h>
 #endif
 
@@ -1705,6 +1709,7 @@
 }
 
 

+#if MINI_GMP_ENABLE_FLOAT
 /* Conversions and comparison to double. */
 void
 mpz_set_d (mpz_t r, double x)
@@ -1861,6 +1866,7 @@
 	return mpz_cmpabs_d (x, d);
     }
 }
+#endif /* MINI_GMP_ENABLE_FLOAT */
 
 

 /* MPZ comparisons and the like. */
diff -r 1dc7d5dabc8d mini-gmp/mini-mpq.c
--- a/mini-gmp/mini-mpq.c	Fri Sep 19 17:18:39 2025 +0200
+++ b/mini-gmp/mini-mpq.c	Wed Sep 24 08:59:37 2025 +0200
@@ -41,6 +41,10 @@
 
 #include "mini-mpq.h"
 
+#ifndef MINI_GMP_ENABLE_FLOAT
+#define MINI_GMP_ENABLE_FLOAT 1
+#endif
+
 #ifndef GMP_LIMB_HIGHBIT
 /* Define macros and static functions already defined by mini-gmp.c */
 #define GMP_LIMB_BITS (sizeof(mp_limb_t) * CHAR_BIT)
@@ -420,6 +424,7 @@
 }
 
 

+#if MINI_GMP_ENABLE_FLOAT
 /* MPQ to/from double. */
 void
 mpq_set_d (mpq_t r, double x)
@@ -472,7 +477,7 @@
 
   return ret;
 }
-
+#endif /* MINI_GMP_ENABLE_FLOAT */
 

 /* MPQ and strings/streams. */
 char *



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