[PATCH] - improve sprintf buffer overflow detection (middle-end/49905)

[Manuel López-Ibáñez]

On 01/07/16 19:15, Martin Sebor wrote:
+	      /* Differentiate between an exact and inexact buffer overflow
+		 or truncation.  */
+	      const char *fmtstr;
+	      if (res->number_chars < 0)
+		fmtstr = info->bounded
+		  ? "output may be truncated at or before format character "
+		    "%qc at offset %qlu past the end of a region of size %qlu"
+		  : "writing format character %qc at offset %qlu "
+		    "in a region of size %qlu";
+	      else
+		fmtstr = info->bounded
+		  ? "output truncated at format character %qc at offset %qlu "
+		    "just past the end of a region of size %qlu"
+		  : "writing format character %qc at offset %qlu "
+		    "just past the end of a region of size %qlu";
+	      warning_at (loc, OPT_Wformat_length_, fmtstr,
+			  format_chars [-1], off - 1,
+			  (unsigned long)info->objsize);
+	    }


I'm not sure gettext can parse the text of format strings given like this. It 
may be smarter enough if the conditional expression is directly the argument to 
warning_at. GCC's -Wformat has the same limitations. Of course, the fool-proof 
way is to use multiple calls to warning_at.

Cheers,
	Manuel.