From bf5b37a3b2b0a286e3cc14d1435f0ddbaa6cee4d Mon Sep 17 00:00:00 2001
From: bbbradsmith <bbbradsmith@users.noreply.github.com>
Date: Tue, 2 May 2023 21:27:02 -0400
Subject: [PATCH] Error check for internal overflow of numerical constant See
 bug #2026

---
 src/cc65/scanner.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/cc65/scanner.c b/src/cc65/scanner.c
index 36fd1301b..055c02450 100644
--- a/src/cc65/scanner.c
+++ b/src/cc65/scanner.c
@@ -522,6 +522,7 @@ static void NumericConst (void)
     char     C;
     unsigned DigitVal;
     unsigned long IVal;         /* Value */
+    int      Overflow;
 
     /* Get the pp-number first, then parse on it */
     CopyPPNumber (&Src);
@@ -575,6 +576,7 @@ static void NumericConst (void)
     /* Since we now know the correct base, convert the input into a number */
     SB_SetIndex (&Src, Index);
     IVal = 0;
+    Overflow = 0;
     while ((C = SB_Peek (&Src)) != '\0' && (Base <= 10 ? IsDigit (C) : IsXDigit (C))) {
         DigitVal = HexVal (C);
         if (DigitVal >= Base) {
@@ -582,9 +584,17 @@ static void NumericConst (void)
             SB_Clear (&Src);
             break;
         }
-        IVal = (IVal * Base) + DigitVal;
+        if ((((unsigned long)(IVal * Base)) / Base) != IVal)
+            Overflow = 1;
+        IVal = IVal * Base;
+        if (((unsigned long)(IVal + DigitVal)) < IVal)
+            Overflow = 1;
+        IVal += DigitVal;
         SB_Skip (&Src);
     }
+    if (Overflow)
+        Error ("Numerical constant \"%s\" too large for internal 32-bit representation",
+               SB_GetConstBuf (&Src));
 
     /* Distinguish between integer and floating point constants */
     if (!IsFloat) {