MODIFIED: Make the Prolog flag float_overflow to affect read_term/3.

With this flag setting, too large floats are read as infinity rather than
raising a syntax error.

man/overview.doc

@@ -1535,7 +1535,9 @@ The smallest representable floating point number above 0.0.  See also
     \prologflagitem{float_overflow}{atom}{rw}
 One of \const{error} (default) or \const{infinity}.  The first is ISO
 compliant.  Using \const{infinity}, floating point overflow is mapped
-to positive or negative \const{Inf}.  See \secref{ieee-float}.
+to positive or negative \const{Inf}.  See \secref{ieee-float}.  This
+flag also affects read_term/3 and friends, causing them to read too
+large floating point number as infinity.
 
     \prologflagitem{float_rounding}{atom}{rw}
 Defines how arithmetic rounds to a float.  Defined values are

src/Tests/core/test_read.pl

@@ -3,7 +3,8 @@
     Author:        Jan Wielemaker
     E-mail:        [email protected]
     WWW:           http://www.swi-prolog.org
-    Copyright (c)  2011-2016, University of Amsterdam
+    Copyright (c)  2011-2023, University of Amsterdam
+			      SWI-Prolog Solutions b.v.
     All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
@@ -46,22 +47,23 @@
 */
 
 test_read :-
-	run_tests([ read_term
-		  ]).
+    run_tests([ read_term,
+		read_numbers
+	      ]).
 
 :- begin_tests(read_term).
 
 test(singletons, Names == ['_a','_A','_0','A']) :-
-	term_string(_, "a(_,_a,_A,_0,A)",
-		    [ singletons(Singletons)
-		    ]),
-	maplist(arg(1), Singletons, Names).
+    term_string(_, "a(_,_a,_A,_0,A)",
+                [ singletons(Singletons)
+                ]),
+    maplist(arg(1), Singletons, Names).
 test(warn_singletons, Messages =@= [singletons(a(_,_,_,_,_), ['_a','A'])]) :-
-	catch_messages(_,
-		       term_string(_, "a(_,_a,_A,_0,A)",
-				   [ singletons(warning)
-				   ]),
-		       Messages).
+    catch_messages(_,
+                   term_string(_, "a(_,_a,_A,_0,A)",
+                               [ singletons(warning)
+                               ]),
+                   Messages).
 test(position,
      [Query,TermPos,Comments] ==
      [true,7-11,['$stream_position'(0,0,0,0)-"%hello"]]) :-
@@ -161,6 +163,20 @@
 
 :- end_tests(read_term).
 
+:- begin_tests(read_numbers).
+
+test(float_overflow, error(syntax_error(float_overflow))) :-
+    term_string(_, '1.797693134862316e+308', []).
+test(float_overflow, F =:= inf) :-
+    current_prolog_flag(float_overflow, Old),
+    setup_call_cleanup(
+        set_prolog_flag(float_overflow, infinity),
+        term_string(F, '1.797693134862316e+308', []),
+        set_prolog_flag(float_overflow, Old)).
+
+:- end_tests(read_numbers).
+
+
 %%	catch_messages(+Kind, :Goal, -Messages) is semidet.
 
 :- thread_local

src/pl-read.c

@@ -2704,9 +2704,17 @@ ascii_to_double(cucharp s, cucharp e, double *dp)
   errno = 0;
   d = strtod((char*)s, &es);
   if ( (cucharp)es == e || (e[0] == '.' && e+1 == (cucharp)es) )
-  { if ( errno == ERANGE && fabs(d) > 1.0 )
-      return NUM_FOVERFLOW;
+  { if ( errno == ERANGE )
+    { GET_LD
 
+      if ( fabs(d) > 1.0 )
+      { if ( !(LD->arith.f.flags & FLT_OVERFLOW) )
+	  return NUM_FOVERFLOW;
+      } else
+      { if ( !(LD->arith.f.flags & FLT_UNDERFLOW) )
+	  return NUM_FOVERFLOW;
+      }
+    }
     *dp = d;
     return NUM_OK;
   }