Fix hex_str and hex_str_upper primitives for negative numbers

lib/sail.c

@@ -164,13 +164,29 @@ void dec_str(sail_string *str, const mpz_t n)
 void hex_str(sail_string *str, const mpz_t n)
 {
   sail_free(*str);
-  gmp_asprintf(str, "0x%Zx", n);
+
+  if (mpz_cmp_si(n, 0) < 0) {
+    mpz_t abs;
+    mpz_init(abs);
+    mpz_abs(abs, n);
+    gmp_asprintf(str, "-0x%Zx", abs);
+  } else {
+    gmp_asprintf(str, "0x%Zx", n);
+  }
 }
 
 void hex_str_upper(sail_string *str, const mpz_t n)
 {
   sail_free(*str);
-  gmp_asprintf(str, "0x%ZX", n);
+
+  if (mpz_cmp_si(n, 0) < 0) {
+    mpz_t abs;
+    mpz_init(abs);
+    mpz_abs(abs, n);
+    gmp_asprintf(str, "-0x%ZX", abs);
+  } else {
+    gmp_asprintf(str, "0x%ZX", n);
+  }
 }
 
 bool eq_string(const_sail_string str1, const_sail_string str2)

src/lib/sail_lib.ml

@@ -1075,6 +1075,7 @@ let to_lower_hex_char n = if 10 <= n && n <= 15 then Char.chr (n + 87) else Char
 let to_upper_hex_char n = if 10 <= n && n <= 15 then Char.chr (n + 55) else Char.chr (n + 48)
 
 let hex_str_helper to_char x =
+  let x, negative = if Big_int.less x Big_int.zero then (Big_int.abs x, "-") else (x, "") in
   if Big_int.equal x Big_int.zero then "0x0"
   else (
     let x = ref x in
@@ -1084,7 +1085,7 @@ let hex_str_helper to_char x =
       s := String.make 1 (to_char lower_4) ^ !s;
       x := Big_int.shift_right !x 4
     done;
-    "0x" ^ !s
+    negative ^ "0x" ^ !s
   )
 
 let hex_str = hex_str_helper to_lower_hex_char

test/c/hex_str_negative.expect

@@ -0,0 +1,6 @@
+0xa
+0xA
+-0xa
+-0xA
+0x0
+0x0

test/c/hex_str_negative.sail

@@ -0,0 +1,15 @@
+default Order dec
+
+$include <prelude.sail>
+$include <string.sail>
+
+val main : unit -> unit
+
+function main() = {
+    print_endline(hex_str(10));
+    print_endline(hex_str_upper(10));
+    print_endline(hex_str(-10));
+    print_endline(hex_str_upper(-10));
+    print_endline(hex_str(0));
+    print_endline(hex_str(0));
+}