parser: catch out-of-range floats.

* parser.l (out_of_range_float): New static function.
(grammar): Check for flo_str returning nil in several places;
that value is returned for out of range floats. This is not
documented!

* txr.1: Document athat flo-str returns nil for out-of-range
floats.

2 files changed, 20 insertions, 3 deletions

diff --git a/parser.l b/parser.l
index 7a9d8d8b..c0114b24 100644
--- a/parser.l
+++ b/parser.l
@@ -137,6 +137,12 @@ static void yyerrprepf(scanner_t *scanner, val fmt, ...)
   }
 }
 
+static void out_of_range_float(scanner_t *scanner, val tok)
+{
+    yyerrorf(scanner, lit("out-of-range floating-point literal: ~a"),
+             tok, nao);
+}
+
 static wchar_t char_esc(int letter)
 {
   switch (letter) {
@@ -344,7 +350,9 @@ UONLY   {U2}{U}|{U3}{U}{U}|{U4}{U}{U}{U}
       || yy_top_state(yyscanner) == QWLIT)
     yy_pop_state(yyscanner);
 
-  yylval->val = flo_str(str);
+  if ((yylval->val = flo_str(str)) == nil)
+    out_of_range_float(yyg, str);
+
   return NUMBER;
 }
 
@@ -360,7 +368,9 @@ UONLY   {U2}{U}|{U3}{U}{U}|{U4}{U}{U}{U}
       || yy_top_state(yyscanner) == QWLIT)
     yy_pop_state(yyscanner);
 
-  yylval->val = flo_str(str);
+  if ((yylval->val = flo_str(str)) == nil)
+    out_of_range_float(yyg, str);
+
   return NUMBER;
 }
 
@@ -372,7 +382,9 @@ UONLY   {U2}{U}|{U3}{U}{U}|{U4}{U}{U}{U}
       || yy_top_state(yyscanner) == QWLIT)
     yy_pop_state(yyscanner);
 
-  yylval->val = flo_str(str);
+  if ((yylval->val = flo_str(str)) == nil)
+    out_of_range_float(yyg, str);
+
   return NUMBER;
 }
 
diff --git a/txr.1 b/txr.1
index 7f2c5cf9..89f6c32e 100644
--- a/txr.1
+++ b/txr.1
@@ -36741,6 +36741,11 @@ part denoted by the letter
 or
 .codn e ,
 an optional sign and one or more optional exponent digits.
+If the value specified by
+.meta string
+is out of range of the floating-point representation, then
+.code nil
+is returned.
 
 The
 .code num-str