From a3c65be91a55c8aff5884b1185ecbc9d42afb4d7 Mon Sep 17 00:00:00 2001
From: Jacob Yen <jacobyen2001@gmail.com>
Date: Fri, 30 Oct 2026 21:51:51 +0800
Subject: [PATCH] Fix ClearFlag indexing and flag-range diagnostics

---
 check/fixes.frm    | 36 ++++++++++++++++++++++++++++++++++++
 sources/compcomm.c |  6 +++---
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/check/fixes.frm b/check/fixes.frm
index 94c7198c..35604af8 100644
--- a/check/fixes.frm
+++ b/check/fixes.frm
@@ -5613,3 +5613,39 @@ Print;
 assert succeeded?
 assert result("test") =~ expr("0")
 *--#] PullReq860_3 :
+
+*--#[ Issue855 :
+L F = 1;
+#do i=1,16
+  #setflag `i',F
+#enddo
+ClearFlag 1,5,16;
+.sort
+#do i=1,16
+  #if flag(`i',F)
+    #message flag(`i',F) is set
+  #else
+    #message flag(`i',F) is clear
+  #endif
+#enddo
+.end
+assert succeeded?
+(1..16).each do |i|
+  expected = [1, 5, 16].include?(i) ? "clear" : "set"
+  assert stdout.include?("~~~flag(#{i},F) is #{expected}")
+end
+*--#] Issue855 :
+
+*--#[ Issue855_SetFlagRange :
+L F = 1;
+SetFlag 0;
+.end
+assert compile_error?("Flag number 0 outside the permitted range 1-")
+*--#] Issue855_SetFlagRange :
+
+*--#[ Issue855_ClearFlagRange :
+L F = 1;
+ClearFlag 999;
+.end
+assert compile_error?("Flag number 999 outside the permitted range 1-")
+*--#] Issue855_ClearFlagRange :
diff --git a/sources/compcomm.c b/sources/compcomm.c
index 4c281613..7363a42f 100644
--- a/sources/compcomm.c
+++ b/sources/compcomm.c
@@ -7428,7 +7428,7 @@ int CoSetUserFlag(UBYTE *s)
 		int x = 0;
 		while ( *s && ( FG.cTable[*s] == 1 ) ) x = 10*x+(*s++ - '0');
 		if ( x < 1 || x > BITSINWORD ) {
-			MesPrint("&Flag number %d outside the permitted range 1-%d.",BITSINWORD);
+			MesPrint("&Flag number %d outside the permitted range 1-%d.",x,BITSINWORD);
 			error = 1;
 		}
 		else {
@@ -7456,11 +7456,11 @@ int CoClearUserFlag(UBYTE *s)
 		int x = 0;
 		while ( *s && ( FG.cTable[*s] == 1 ) ) x = 10*x+(*s++ - '0');
 		if ( x < 1 || x > BITSINWORD ) {
-			MesPrint("&Flag number %d outside the permitted range 1-%d.",BITSINWORD);
+			MesPrint("&Flag number %d outside the permitted range 1-%d.",x,BITSINWORD);
 			error = 1;
 		}
 		else {
-			Add3Com(TYPECLEARUSERFLAG,x);
+			Add3Com(TYPECLEARUSERFLAG,x-1);
 		}
 		while ( *s && ( *s == ',' || *s == ' ' || *s == '\t' ) ) s++;
 	}