🚀 go-pugleaf

GCC 2.3.1 (sparc, SunOS 4.1.2) doesn't catch the signed integer overflows in
either of the following constant expression initializers.

	signed char c = 256;
	long long x = 9223372036854775808ULL;

The first line isn't diagnosed because force_fit_type yields a nonzero value
that isn't 1, and this value overflows when it is assigned to a 1-bit field.

The second line isn't diagnosed because the overflow occurs as a function of
changing the value from unsigned to signed; force_fit_type can't see this.

Here is a patch.  The last hunk of this patch fixes the second bug; the
rest of the patch fixes the first bug.

Thu Nov 12 05:32:24 1992  Paul Eggert  (eggert@twinsun.com)

	* fold-const.c (force_fit_type): Yield 0 or 1, so that result fits in
	a 1-bit field.
	(fold-convert): Report an overflow if a large unsigned long long value
	converts to a negative signed long long value.

===================================================================
RCS file: fold-const.c,v
retrieving revision 2.3.1.7
retrieving revision 2.3.1.8
diff -c -r2.3.1.7 -r2.3.1.8
*** fold-const.c	1992/11/10 19:20:24	2.3.1.7
--- fold-const.c	1992/11/12 05:32:24	2.3.1.8
***************
*** 117,123 ****
  /* Make the integer constant T valid for its type
     by setting to 0 or 1 all the bits in the constant
     that don't belong in the type.
!    Yield nonzero if a signed overflow occurs.
     If OVERFLOW is nonzero, a signed overflow has already occurred.  */
  
  static int
--- 117,123 ----
  /* Make the integer constant T valid for its type
     by setting to 0 or 1 all the bits in the constant
     that don't belong in the type.
!    Yield 1 if a signed overflow occurs, 0 otherwise.
     If OVERFLOW is nonzero, a signed overflow has already occurred.  */
  
  static int
***************
*** 175,182 ****
  
    /* Yield nonzero if signed overflow occurred.  */
    return
!     (overflow
!      | (low ^ TREE_INT_CST_LOW (t)) | (high ^ TREE_INT_CST_HIGH (t)) != 0);
  }
  
  /* Add two doubleword integers with doubleword result.
--- 175,182 ----
  
    /* Yield nonzero if signed overflow occurred.  */
    return
!     ((overflow | (low ^ TREE_INT_CST_LOW (t)) | (high ^ TREE_INT_CST_HIGH (t)))
!      != 0);
  }
  
  /* Add two doubleword integers with doubleword result.
***************
*** 1490,1495 ****
--- 1490,1497 ----
  	  TREE_TYPE (t) = type;
  	  TREE_CONSTANT_OVERFLOW (t) =
  	    (TREE_CONSTANT_OVERFLOW (arg1)
+ 	     | (TREE_INT_CST_HIGH (arg1) < 0
+ 		& TREE_UNSIGNED (type) < TREE_UNSIGNED (TREE_TYPE (arg1)))
  	     | force_fit_type (t, 0));
  	}
  #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)