1 files changed, 35 insertions, 56 deletions

diff --git a/base/string_util.cc b/base/string_util.cc
index bd02f3d..31f97131b 100644
--- a/base/string_util.cc
+++ b/base/string_util.cc
@@ -27,6 +27,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// StringPrintf stuff based on strings/stringprintf.cc by Sanjay Ghemawat
+
 #include "base/string_util.h"
 
 #include <ctype.h>
@@ -45,6 +47,7 @@
 
 #include "base/basictypes.h"
 #include "base/logging.h"
+#include "base/scoped_ptr.h"
 #include "base/singleton.h"
 
 namespace {
@@ -760,10 +763,9 @@ void ReplaceSubstringsAfterOffset(std::string* str,
 
 // Overloaded wrappers around vsnprintf and vswprintf. The buf_size parameter
 // is the size of the buffer. These return the number of characters in the
-// formatted string excluding the NUL terminator. If the buffer is not
-// large enough to accommodate the formatted string without truncation, they
-// return the number of characters that would be in the fully-formatted string
-// (vsnprintf, and vswprintf on Windows), or -1 (vswprintf on POSIX platforms).
+// formatted string excluding the NUL terminator, or if the buffer is not
+// large enough to accommodate the formatted string without truncation, the
+// number of characters that would be in the fully-formatted string.
 inline int vsnprintfT(char* buffer,
                       size_t buf_size,
                       const char* format,
@@ -787,69 +789,46 @@ static void StringAppendVT(
     va_list ap) {
 
   // First try with a small fixed size buffer.
-  // This buffer size should be kept in sync with StringUtilTest.GrowBoundary
-  // and StringUtilTest.StringPrintfBounds.
-  char_type stack_buf[1024];
-
-  va_list backup_ap;
-  base::va_copy(backup_ap, ap);
-
-#if !defined(OS_WIN)
-  errno = 0;
-#endif
-  int result = vsnprintfT(stack_buf, arraysize(stack_buf), format, backup_ap);
+  // This buffer size should be kept in sync with StringUtilTest.GrowBoundary.
+  const int kStackLength = 1024;
+  char_type stack_buf[kStackLength];
+
+  // It's possible for methods that use a va_list to invalidate the data in it
+  // upon use.  The fix is to make a copy of the structure before using it and
+  // use that copy instead. It is not guaranteed that assignment is a copy, and
+  // va_copy is not supported by VC, so the UnitTest tests this capability.
+  va_list backup_ap = ap;
+  int result = vsnprintfT(stack_buf, kStackLength, format, backup_ap);
   va_end(backup_ap);
 
-  if (result >= 0 && result < static_cast<int>(arraysize(stack_buf))) {
+  if (result >= 0 && result < kStackLength) {
     // It fit.
     dst->append(stack_buf, result);
     return;
   }
 
-  // Repeatedly increase buffer size until it fits.
-  int mem_length = arraysize(stack_buf);
-  while (true) {
-    if (result < 0) {
-#if !defined(OS_WIN)
-      // On Windows, vsnprintfT always returns the number of characters in a
-      // fully-formatted string, so if we reach this point, something else is
-      // wrong and no amount of buffer-doubling is going to fix it.
-      if (errno != 0 && errno != EOVERFLOW)
-#endif
-      {
-        // If an error other than overflow occurred, it's never going to work.
-        DLOG(WARNING) << "Unable to printf the requested string due to error.";
-        return;
-      }
-      // Try doubling the buffer size.
-      mem_length *= 2;
-    } else {
-      // We need exactly "result + 1" characters.
-      mem_length = result + 1;
-    }
-
-    if (mem_length > 32 * 1024 * 1024) {
-      // That should be plenty, don't try anything larger.  This protects
-      // against huge allocations when using vsnprintfT implementations that
-      // return -1 for reasons other than overflow without setting errno.
-      DLOG(WARNING) << "Unable to printf the requested string due to size.";
-      return;
-    }
-
-    std::vector<char_type> mem_buf(mem_length);
+  int mem_length = result;
 
-    // Restore the va_list before we use it again.
-    base::va_copy(backup_ap, ap);
+  // vsnprintfT may have failed for some reason other than an insufficient
+  // buffer, such as an invalid characer.  Check that the requested buffer
+  // size is smaller than what was already attempted
+  if (mem_length < 0 || mem_length < kStackLength) {
+    DLOG(WARNING) << "Unable to compute size of the requested string.";
+    return;
+  }
 
-    result = vsnprintfT(&mem_buf[0], mem_length, format, ap);
-    va_end(backup_ap);
+  mem_length++;  // Include the NULL terminator.
+  scoped_ptr<char_type> mem_buf(new char_type[mem_length]);
 
-    if ((result >= 0) && (result < mem_length)) {
-      // It fit.
-      dst->append(&mem_buf[0], result);
-      return;
-    }
+  // Do the printf.
+  result = vsnprintfT(mem_buf.get(), mem_length, format, ap);
+  DCHECK(result < mem_length);
+  if (result < 0) {
+    DLOG(WARNING) << "Unable to printf the requested string.";
+    return;
   }
+
+  dst->append(mem_buf.get(), result);
 }
 
 std::string Uint64ToString(uint64 value) {