(patch) IniWriteFloat should limit its field width

[Explorer09]

IniWriteFloat should limit its field width, otherwise it is easy to create a buffer overflow with a large floating point number. The syntax like sprintf(buf, "%f", num) is unsafe.

Ideally snprintf should be used instead of sprintf, but I assume not every system support that (it's C99, but some systems supports sprintf_s), and it takes time to write it in a backward-compatible way, so I guess I'll hold that for now and do it when I have more time.

However limiting the field width of float-to-string output always works.

The reverse functions, atof and strtod, always accept input in E notation.

diff -r -u a/commonc.c b/commonc.c
--- a/commonc.c	2015-03-26 05:27:12.000000000 +0800
+++ b/commonc.c	2015-09-23 08:12:44.936980349 +0800
@@ -1745,8 +1745,10 @@
 	const char *keyword,
 	float	val)
 {
+	/* Assume FLT_MAX is 3.40282e+038, the maximum significant digits that
+	can be stored in this buf is 12. ((sizeof(buf))-sizeof("-.E+038")) */
 	char	buf[20];
-	sprintf (buf, "%f", val);
+	sprintf (buf, "%11g", val);
 	IniSectionWriteString (filename, section, keyword, buf);
 }