prayer fix for being in poison gas cloud region

Like stuck-in-wall, there might not be any place to move the hero
in order to escape a poison gas cloud.  That could result in "fix
all troubles" becoming stuck in a loop.  3.6.something fixed the
stuck-in-wall case by temporarily conferring Passes_walls.  Fix the
in-poison-region case by temporarily conferring Magical_breathing.

Not adequately tested...

I don't think that this fixes "#K4252: NH 3.7 Prayer Bug" where the
game hung during a couple out of scores of prayers.  I didn't see
any other fix-trouble cases that seemed likely to remain unfixed
and end up with repair attempts retrying.

src/do_wear.c

@@ -1,4 +1,4 @@
-/* NetHack 3.7	do_wear.c	$NHDT-Date: 1720895740 2024/07/13 18:35:40 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.188 $ */
+/* NetHack 3.7	do_wear.c	$NHDT-Date: 1727251255 2024/09/25 08:00:55 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.191 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2012. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -940,9 +940,24 @@ Amulet_on(void)
     case AMULET_OF_LIFE_SAVING:
     case AMULET_VERSUS_POISON:
     case AMULET_OF_REFLECTION:
-    case AMULET_OF_MAGICAL_BREATHING:
     case FAKE_AMULET_OF_YENDOR:
         break;
+    case AMULET_OF_MAGICAL_BREATHING: {
+        boolean was_in_poison_gas;
+
+        /* amulet is already on; we need to check hero's gas-cloud status
+           when it was off */
+        EMagical_breathing &= ~W_AMUL;
+        was_in_poison_gas = region_danger();
+        EMagical_breathing |= W_AMUL;
+        if (was_in_poison_gas) {
+            You("are no longer bothered by the poison gas.");
+            makeknown(AMULET_OF_MAGICAL_BREATHING);
+        }
+        /* no need to check for becoming able to breathe underwater;
+           if we are underwater, we already can or we would have drowned */
+        break;
+    }
     case AMULET_OF_UNCHANGING:
         if (Slimed)
             make_slimed(0L, (char *) 0);
@@ -1039,8 +1054,7 @@ Amulet_off(void)
         break;
     case AMULET_OF_MAGICAL_BREATHING:
         if (Underwater) {
-            /* HMagical_breathing must be set off
+            /* HMagical_breathing must be set off before calling drown() */
-                before calling drown() */
             setworn((struct obj *) 0, W_AMUL);
             if (!cant_drown(gy.youmonst.data) && !Swimming) {
                 You("suddenly inhale an unhealthy amount of %s!",
@@ -1049,6 +1063,9 @@ Amulet_off(void)
             }
             return;
         }
+        /*
+         * FIXME: we need a poison gas region check here
+         */
         break;
     case AMULET_OF_STRANGULATION:
         if (Strangled) {

src/region.c

@@ -1,4 +1,4 @@
-/* NetHack 3.7	region.c	$NHDT-Date: 1723580898 2024/08/13 20:28:18 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.98 $ */
+/* NetHack 3.7	region.c	$NHDT-Date: 1727251269 2024/09/25 08:01:09 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.104 $ */
 /* Copyright (c) 1996 by Jean-Christophe Collet  */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -1410,7 +1410,14 @@ region_safety(void)
 
     if (n > 1 || (n == 1 && !r)) {
         /* multiple overlapping cloud regions or non-expiring one */
-        safe_teleds(TELEDS_NO_FLAGS);
+        (void) safe_teleds(TELEDS_NO_FLAGS);
+        /* maybe there's no safe place available; must get hero out of danger
+           or prayer's "fix all troubles" result will get stuck in a loop */
+        if (region_danger()) {
+            set_itimeout(&HMagical_breathing, (long) (d(4, 4) + 4));
+            /* not already Breathless or wouldn't be in region danger */
+            You_feel("able to breathe.");
+        }
     } else if (r) {
         remove_region(r);
         pline_The("gas cloud enveloping you dissipates.");

src/timeout.c

@@ -1,4 +1,4 @@
-/* NetHack 3.7	timeout.c	$NHDT-Date: 1723580900 2024/08/13 20:28:20 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.190 $ */
+/* NetHack 3.7	timeout.c	$NHDT-Date: 1727251273 2024/09/25 08:01:13 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.193 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2018. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -56,6 +56,8 @@ static const struct propname {
     /* timed pass-walls is a potential prayer result if surrounded by stone
        with nowhere to be safely teleported to */
     { PASSES_WALLS, "pass thru walls" },
+    /* likewise for magical breathing vs poison gas regions */
+    { MAGICAL_BREATHING, "magical breathing" },
     /* timed fire resistance and water walking are possible in explore mode
        (as well as in wizard mode) after life-saving in lava if it fails to
        teleport the hero to safety and player declines to die */
@@ -92,7 +94,6 @@ static const struct propname {
     { TELEPORT_CONTROL, "teleport control" },
     { FLYING, "flying" },
     { SWIMMING, "swimming" },
-    { MAGICAL_BREATHING, "magical breathing" },
     { SLOW_DIGESTION, "slow digestion" },
     { HALF_SPDAM, "half spell damage" },
     { HALF_PHDAM, "half physical damage" },
@@ -534,7 +535,33 @@ phaze_dialogue(void)
         return;
 
     if (((HPasses_walls & TIMEOUT) % 2L) && i > 0L && i <= SIZE(phaze_texts))
-        pline1(phaze_texts[SIZE(phaze_texts) - i]);
+        pline("%s", phaze_texts[SIZE(phaze_texts) - i]);
+}
+
+/* Similar to Passes_walls, if prayer tries to save hero from a poison
+   gas region but can't, (HMagical_breathing & TIMEOUT) will be set to
+   a small value.  Unlike Passes_walls, there's no joke message. */
+static NEARDATA const char *const region_texts[] = {
+    "You seem to have some trouble breathing.",
+    "The air here seems foul.",
+};
+
+staticfn void
+region_dialogue(void)
+{
+    boolean breathless, in_poison_gas_cloud;
+    long r = (HMagical_breathing & TIMEOUT), i = r / 2L;
+
+    /* might have poly'd into non-breather or moved out of gas cloud */
+    HMagical_breathing &= ~TIMEOUT;
+    breathless = breathless(&mons[u.umonnum]);
+    in_poison_gas_cloud = region_danger();
+    HMagical_breathing |= r;
+    if (breathless || !in_poison_gas_cloud)
+        return;
+
+    if ((r % 2L) && i > 0L && i <= SIZE(region_texts))
+        pline("%s", region_texts[SIZE(region_texts) - i]);
 }
 
 /* when a status timeout is fatal, keep the status line indicator shown
@@ -600,6 +627,8 @@ nh_timeout(void)
         levitation_dialogue();
     if (HPasses_walls & TIMEOUT)
         phaze_dialogue();
+    if (HMagical_breathing & TIMEOUT)
+        region_dialogue();
     if (HSleepy & TIMEOUT)
         sleep_dialogue();
     if (u.mtimedone && !--u.mtimedone) {
@@ -844,6 +873,13 @@ nh_timeout(void)
                               !Upolyd ? "normal" : "unusual");
                 }
                 break;
+            case MAGICAL_BREATHING:
+                if (!Breathless) {
+                    if (region_danger())
+                        You("cough%s",
+                            Poison_resistance ? "." : " and spit blood!");
+                }
+                break;
             case STRANGLED:
                 svk.killer.format = KILLED_BY;
                 Strcpy(svk.killer.name,