Fix #9871 by making jl_substrtod whitespace-tolerant

src/builtins.c

@@ -755,9 +755,16 @@ DLLEXPORT int jl_substrtod(char *str, size_t offset, int len, double *out)
         pend = bstr+len;
     }
     *out = strtod_c(bstr, &p);
-    if ((p == bstr) || (p != pend) ||
+    if (p == bstr ||
         (errno==ERANGE && (*out==0 || *out==HUGE_VAL || *out==-HUGE_VAL)))
         err = 1;
+    // Deal with case where the substring might be something like "1 ",
+    // which is OK, and "1 X", which we don't allow.
+    while (p != pend) {
+        if (!isspace((unsigned char)*p))
+            return 1;
+        p++;
+    }
     if (bstr != str+offset)
         free(bstr);
     return err;

test/strings.jl

@@ -1305,3 +1305,11 @@ for T in (ASCIIString, UTF8String, UTF16String, UTF32String)
         end
     end
 end
+
+# issue #9781
+# float(SubString) wasn't tolerant of trailing whitespace, which was different
+# to "normal" strings. This also checks we aren't being too tolerant and allowing
+# any arbitrary trailing characters.
+@test float("1\n") == 1.0
+@test float(split("0,1\n",","))[2] == 1.0
+@test_throws ArgumentError float(split("0,1 X\n",","))[2]