[STDCXX-765] Incorrect using rw_asnprintf() with %{+} format and not NUL-terminated buffer in _rw_fmtflags(), _rw_fmtevent(), _rw_fmtlc()

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.2.0
• Fix Version/s: 4.2.1
• Component/s: Test Driver

Environment

All

• Severity: Incorrect Behavior
• Assignee: Martin Sebor
• Reporter: Farid Zaripov
• Created: 15/Mar/08 15:27
• Updated: 17/Apr/08 11:08
• Resolved: 18/Mar/08 14:54

Description

The buf parameter of the _rw_fmtflags(), _rw_fmtevent() and _rw_fmtlc() functions contains not NUL-terminated data. The length of data in buf is stored in buf.endoff.
The rw_asnprintf() function accepts the only buf.pbuf and buf.pbufsize, but not buf.endoff. When %{+} format is used, the length of data in buf calculated using strlen() function, but this length is incorrect due to data is not NUL-terminated.
Another bug is that _rw_fmtflags(), _rw_fmtevent() and _rw_fmtlc() functions are returns len, but without updating the buf.endoff. Due to this the result of rw_asnprintf() is cutted in further processing.

These problems are detected in 0.printf test after latest update.

The schematic patch without error checking is below. This patch is not intended to apply. It's only shows how these bugs should be fixed.

Index: tests/src/fmt_bits.cpp
===================================================================
--- tests/src/fmt_bits.cpp	(revision 637399)
+++ tests/src/fmt_bits.cpp	(working copy)
@@ -204,9 +204,12 @@
 
 #endif   // _RWSTD_NO_EXT_BIN_IO
 
-        len = rw_asnprintf (buf.pbuf, buf.pbufsize,
-                            "%{+} | %{?}std::ios::%{;}base(%d)",
-                            spec.fl_pound, base);
+        (*buf.pbuf) [buf.endoff] = '\0';
+        int res = rw_asnprintf (buf.pbuf, buf.pbufsize,
+                                "%{+} | %{?}std::ios::%{;}base(%d)",
+                                spec.fl_pound, base);
+        buf.endoff += res;
+        len += res;
     }
 
     return len;
@@ -303,9 +306,12 @@
         : std::ios::erase_event   == event ? "erase_event"
         : 0;
 
-    return rw_asnprintf (buf.pbuf, buf.pbufsize,
-                         "%{+}%{?}std::ios::%{;}%{?}%s%{:}event(%d)%{;}",
-                         spec.fl_pound, 0 != str, str, event);
+    (*buf.pbuf) [buf.endoff] = '\0';
+    int len = rw_asnprintf (buf.pbuf, buf.pbufsize,
+                            "%{+}%{?}std::ios::%{;}%{?}%s%{:}event(%d)%{;}",
+                            spec.fl_pound, 0 != str, str, event);
+    buf.endoff += len;
+    return len;
 }
 
 /********************************************************************/
@@ -329,8 +335,12 @@
 
     }
 
-    if (str)
-        return rw_asnprintf (buf.pbuf, buf.pbufsize, "%{+}%s", str);
+    if (str) {
+        (*buf.pbuf) [buf.endoff] = '\0';
+        int len = rw_asnprintf (buf.pbuf, buf.pbufsize, "%{+}%s", str);
+        buf.endoff += len;
+        return len;
+    }
 
     static const Bitnames names [] = {
         BITNAME (std::locale, all),