lib: defend against locale-specific wcstod.

The wcstod function has locale-specific behavior. It uses a
locale-specific decimal separator character, which may not be
the period.  Though in TXR we never call setlocale in order to
activate localization, it is a good idea to put in code to
defend against this. If locale is ever unleashed on the code,
it really botches our floating-point handling. However, let's
keep that defensive logic disabled for now using the
preprocessor.

The strategy is to inquire about the locale's decimal
character at startup. Then, in the flo_str function, we
preprocess the input by converting the decimal period to
the locale-specific character before calling wcstod. On the
output side, we also deal with it in the format function; we
call sprintf, and then convert the locale-specific characer
to period.

I tested all this by temporarily introducing the setlocale
call, and switching to a locale with a comma as the separator,
geting make tests to pass, and doing some interactive testing.
This is not going to receive coverage in the test suite.

* lib.c (dec_point): New global variable.
(flo_str): If dec_point isn't '.', we must copy the
string into a local buffer, which we get from alloca, and
edit any '.' that it contains to dec_point.
(locale_init): New function; initializes dec_point.
(init): Call locale_init.

* lib.h (dec_point): Declared.

* stream.c (formatv): Don't look for a '.' in the result of
printing a double using %e; look for dec_point. Post-process
floating-point sprinf by substituting occurrences of dec_point
with the period.

1 files changed, 20 insertions, 1 deletions

diff --git a/stream.c b/stream.c
index ef2c0a29..07a0060c 100644
--- a/stream.c
+++ b/stream.c
@@ -3494,7 +3494,11 @@ val formatv(val stream_in, val fmtstr, struct args *al)
             if (ch == 'e') {
               sprintf(num_buf, "%.*e", precision, n);
               {
+#if CONFIG_LOCALE_TOLERANCE
+                char *dec = strchr(num_buf, dec_point);
+#else
                 char *dec = strchr(num_buf, '.');
+#endif
                 char *exp = strchr(dec ? dec : num_buf, 'e');
 
                 if (exp) {
@@ -3525,6 +3529,13 @@ val formatv(val stream_in, val fmtstr, struct args *al)
               continue;
             }
             precision = (width ? width - 1 : 0);
+#if CONFIG_LOCALE_TOLERANCE
+            if (dec_point != '.') {
+              char *dot = num_buf;
+              while ((dot = strchr(dot, dec_point)) != 0)
+                *dot++ = '.';
+            }
+#endif
             goto output_num;
           }
         case 'd':
@@ -3584,6 +3595,14 @@ val formatv(val stream_in, val fmtstr, struct args *al)
 
             sprintf(num_buf, "%.*g", precision, obj->fl.n);
 
+#if CONFIG_LOCALE_TOLERANCE
+            if (dec_point != '.') {
+              char *dot = num_buf;
+              while ((dot = strchr(dot, dec_point)) != 0)
+                *dot++ = '.';
+            }
+#endif
+
             {
               char *dec = strchr(num_buf, '.');
               char *exp = strchr(dec ? dec : num_buf, 'e');
@@ -3606,7 +3625,7 @@ val formatv(val stream_in, val fmtstr, struct args *al)
               }
 
               if (ch == 's' && (!precision_p || precision > 0) && !dec && !exp)
-                  strcat(num_buf, ".0");
+                strcat(num_buf, ".0");
             }
 
             if (!isdigit(num_buf[0]) && !isdigit(num_buf[1])) {