From: NHOrus <jy6x2b32pie9@yahoo.com>
Date: Mon, 11 Sep 2017 18:20:46 +0000 (+0300)
Subject: If divident negative, then remainder is negative too.
X-Git-Tag: 1.5~17
X-Git-Url: https://jxself.org/git/?a=commitdiff_plain;h=076bb8908bf76e25e9178c178321a7f690b002d8;p=open-adventure.git

If divident negative, then remainder is negative too.
RNG values need to be always positive.
Solution: Transposing positively by divisor. In all the two places it may happen.
---

diff --git a/misc.c b/misc.c
index 302e61c..80e4352 100644
--- a/misc.c
+++ b/misc.c
@@ -646,8 +646,10 @@ bool tstbit(long mask, int bit)
 void set_seed(int32_t seedval)
 /* Set the LCG seed */
 {
-    game.lcg_x = (uint32_t) seedval % LCG_M;
-
+    game.lcg_x = seedval % LCG_M;
+    if (game.lcg_x < 0) {
+        game.lcg_x = LCG_M + game.lcg_x;
+    }
     // once seed is set, we need to generate the Z`ZZZ word
     for (int i = 0; i < 5; ++i) {
         game.zzword[i] = 'A' + randrange(26);
diff --git a/saveresume.c b/saveresume.c
index f1d52d4..8bd4418 100644
--- a/saveresume.c
+++ b/saveresume.c
@@ -145,6 +145,11 @@ bool is_valid(struct game_t* valgame)
         valgame->lcg_x %= LCG_M;
     }
 
+    /* Check for RNG underflow. Transpose */
+    if (valgame->lcg_x < LCG_M) {
+        valgame->lcg_x = LCG_M + (valgame->lcg_x % LCG_M);
+    }
+
     /*  Bounds check for locations */
     if ( valgame->chloc  < -1 || valgame->chloc  > NLOCATIONS ||
          valgame->chloc2 < -1 || valgame->chloc2 > NLOCATIONS ||