[gdb/m2] Fix UB and literal truncation

Rewrite parse_number to use ULONGEST instead of LONGEST, to fix UB errors as
mentioned in PR29163.

Furthermore, make sure we error out on overflow instead of truncating in all
cases.

Tested on x86_64-linux, with a build with --enable-targets=all.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29163

1 files changed, 23 insertions, 24 deletions

diff --git a/gdb/m2-exp.y b/gdb/m2-exp.y
index 85bac11..d3e917b 100644
--- a/gdb/m2-exp.y
+++ b/gdb/m2-exp.y
@@ -582,12 +582,11 @@ static int
 parse_number (int olen)
 {
   const char *p = pstate->lexptr;
-  LONGEST n = 0;
-  LONGEST prevn = 0;
+  ULONGEST n = 0;
+  ULONGEST prevn = 0;
   int c,i,ischar=0;
   int base = input_radix;
   int len = olen;
-  int unsigned_p = number_sign == 1 ? 1 : 0;
 
   if(p[len-1] == 'H')
   {
@@ -639,16 +638,11 @@ parse_number (int olen)
       n+=i;
       if(i >= base)
 	 return ERROR;
-      if(!unsigned_p && number_sign == 1 && (prevn >= n))
-	 unsigned_p=1;		/* Try something unsigned */
-      /* Don't do the range check if n==i and i==0, since that special
-	 case will give an overflow error.  */
-      if(RANGE_CHECK && n!=i && i)
-      {
-	 if((unsigned_p && (unsigned)prevn >= (unsigned)n) ||
-	    ((!unsigned_p && number_sign==-1) && -prevn <= -n))
-	    range_error (_("Overflow on numeric constant."));
-      }
+      if (n == 0 && prevn == 0)
+	;
+      else if (RANGE_CHECK && prevn >= n)
+	range_error (_("Overflow on numeric constant."));
+
 	 prevn=n;
     }
 
@@ -661,17 +655,22 @@ parse_number (int olen)
      yylval.ulval = n;
      return CHAR;
   }
-  else if ( unsigned_p && number_sign == 1)
-  {
-     yylval.ulval = n;
-     return UINT;
-  }
-  else if((unsigned_p && (n<0))) {
-     range_error (_("Overflow on numeric constant -- number too large."));
-     /* But, this can return if range_check == range_warn.  */
-  }
-  yylval.lval = n;
-  return INT;
+
+  int int_bits = gdbarch_int_bit (pstate->gdbarch ());
+  bool have_signed = number_sign == -1;
+  bool have_unsigned = number_sign == 1;
+  if (have_signed && fits_in_type (number_sign, n, int_bits, true))
+    {
+      yylval.lval = n;
+      return INT;
+    }
+  else if (have_unsigned && fits_in_type (number_sign, n, int_bits, false))
+    {
+      yylval.ulval = n;
+      return UINT;
+    }
+  else
+    error (_("Overflow on numeric constant."));
 }