The TortoiseSVN log files do not rotate or trim, leading to excessive disk usage

[April Zou]

I noticed that logfile for tortoise can take 4G space of the C disk, which may cause disk shortage. So I reached out to the source code to do secondary development and surprisely found that trimFile function seem not working. 

maxline is set to 4k for default

CLogFile::CLogFile()

{

    m_maxLines = CRegStdDWORD(L"Software\\TortoiseSVN\\MaxLinesInLogfile", 4000);

}

and trimFile function is supposed to handle logFile rotation

void CLogFile::TrimFile(DWORD maxLines) const

{

    if (!PathFileExists(m_logFile.GetWinPath()))

    {

        CTraceToOutputDebugString::Instance()(L"SVNlog::TrimFile: Log file does not exist.");

        return;

    }

    try

    {

        CMappedInFile file(m_logFile.GetWinPath(), true);

        unsigned char* begin = file.GetWritableBuffer();

        unsigned char* end   = begin + file.GetSize();

        CTraceToOutputDebugString::Instance()(L"SVNlog::TrimFile: File path = %s", m_logFile.GetWinPath());

        CTraceToOutputDebugString::Instance()(L"SVNlog::TrimFile: File size = %d bytes", file.GetSize());

        CTraceToOutputDebugString::Instance()(L"SVNlog::TrimFile: begin = 0x%p, end = 0x%p", begin, end);

        CTraceToOutputDebugString::Instance()(L"SVNlog::TrimFile: Number of bytes between begin and end = %d", end - begin);

        if (begin <= (end - 2))

        {

            CTraceToOutputDebugString::Instance()(L"SVNlog::TrimFile: File is too small to trim.");

            return;

        }

        unsigned char* trimPos = begin;

        for (unsigned char* s = end; s != begin; --s)

        {

            if (*(s - 1) == '\n')

            {

                if (maxLines == 0)

                {

                    trimPos = s;

                    break;

                }

                else

                    --maxLines;

            }

        }

        if (trimPos == begin)

        {

            CTraceToOutputDebugString::Instance()(L"SVNlog::TrimFile: No lines need to be trimmed.");

            return;

        }

        CString trimPosStr;

        trimPosStr.Format(L"SVNlog::trimPos: %p", trimPos);

        CTraceToOutputDebugString::Instance()(trimPosStr);

        CString endStr;

        endStr.Format(L"SVNlog::endPos: %p", end);

        CTraceToOutputDebugString::Instance()(endStr);

        size_t newSize = end - trimPos;

        memmove(begin, trimPos, newSize);

        file.Close(newSize);

    }

    catch (CStreamException& e)

    {

        CString errorMsg;

        errorMsg.Format(L"SVNlog::TrimFile: CStreamException while trimming log file: %s", e.what());

        CTraceToOutputDebugString::Instance()(errorMsg);

    }

}

I added some log and use dbgview to capture info, it looks like TrimFile return at byte nums check if (begin <= (end - 2))

I suspect that this condition might be incorrect and should instead be:

if (begin >= (end - 2))

begin >= (end - 2) means the original logFile is less than or equal to 2 bytes which is too small to skip the check. 

```

PS C:\Users\zourui\projects\projfs-tortoisesvn> svn --version
svn, version 1.15.0-unisvn1115 (NTES UNISVN development)
   compiled Jun 11 2024, 18:00:21 on x86-microsoft-windows

```

[Daniel Sahlberg]

Thanks for the report, the analysis is correct. Committed in 29697.

Kind regards,

Daniel