[Lldb-commits] [lldb] r106416 - /lldb/trunk/source/Core/Error.cpp

[Chris Lattner]

On Jun 21, 2010, at 7:34 AM, Benjamin Kramer wrote:

> Author: d0k
> Date: Mon Jun 21 09:34:03 2010
> New Revision: 106416
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=106416&view=rev
> Log:
> Don't snprintf directly into a std::string, it's undefined behavior per C++03.
> 
> This also fixes a bug where we were trying to copy m_string into itself
> via a format string. The pointer was invalidated by m_string.resize and
> lldb (sometimes) crashed inside vsnprintf.

I haven't looked at the surrounding code, but would it be better to change this method to take a Twine?

-Chris

> 
> Modified:
>    lldb/trunk/source/Core/Error.cpp
> 
> Modified: lldb/trunk/source/Core/Error.cpp
> URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Core/Error.cpp?rev=106416&r1=106415&r2=106416&view=diff
> ==============================================================================
> --- lldb/trunk/source/Core/Error.cpp (original)
> +++ lldb/trunk/source/Core/Error.cpp Mon Jun 21 09:34:03 2010
> @@ -15,6 +15,7 @@
> // Project includes
> #include "lldb/Core/Error.h"
> #include "lldb/Core/Log.h"
> +#include "llvm/ADT/SmallVector.h"
> #include <cstdarg>
> #include <cstdlib>
> #include <cstring>
> @@ -327,27 +328,23 @@
>             SetErrorToGenericError();
> 
>         // Try and fit our error into a 1024 byte buffer first...
> -        m_string.resize(1024);
> +        llvm::SmallVector<char, 1024> buf;
> +        buf.resize(1024);
>         // Copy in case our first call to vsnprintf doesn't fit into our
>         // allocated buffer above
>         va_list copy_args;
>         va_copy (copy_args, args);
> -        int length = ::vsnprintf (&m_string[0], m_string.size(), format, args);
> -        if (length < m_string.size())
> -        {
> -            // The error formatted string fit into our buffer, just chop it down
> -            // to size
> -            m_string.erase (length);
> -        }
> -        else
> +        int length = ::vsnprintf (buf.data(), buf.size(), format, args);
> +        if (length >= buf.size())
>         {
>             // The error formatted string didn't fit into our buffer, resize it
>             // to the exact needed size, and retry
> -            m_string.resize(length + 1);
> -            length = ::vsnprintf (&m_string[0], m_string.size(), format, copy_args);
> +            buf.resize(length + 1);
> +            length = ::vsnprintf (buf.data(), buf.size(), format, copy_args);
>             va_end (copy_args);
> -            assert (length < m_string.size());
> +            assert (length < buf.size());
>         }
> +        m_string.assign(buf.data(), length);
>         va_end (args);
>         return length;
>     }
> 
> 
> _______________________________________________
> lldb-commits mailing list
> lldb-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits