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From Zhou Tao <zhoutao...@gmail.com>
Subject Re: LOG4CXX_DECODE_CHAR Crash on windows
Date Tue, 17 Nov 2009 08:39:12 GMT
I take a look at the problem. The issue is caused by using mixed MT/MD
option in one process. My DLL is using MT option and log4cxx is using MD, so
they are using different copy of CRT lib. I call the LOG4CXX_DECODE_CHAR
macro within my DLL to create a LogString variable then get the fail. (
note: in debug mode on windows32).

Macro:
#define LOG4CXX_DECODE_CHAR(var, src) \
log4cxx::LogString var; \
log4cxx::helpers::Transcoder::decode(src, var)

I check the Transcoder::decode(const std::string& src, LogString& dst)
function,

dst.reserve(dst.size()+src.size());

The above statement maybe allocate new bytes in the CRT heap used by
log4cxx, but the dst variable would be freed in my DLL if I use the macro.
The two DLLs have two different copy of CRT libs. So cause a heap corruption
error.

I understand if all DLLs are build with MD option, then OK.

So my question is,
1. the macro LOG4CXX_DECODE_CHAR(var, src) is only used for log4cxx DLL
internally?
2. Why not to only fill the memory in decode function, but not to change the
size of the passed-in CRT objects? It's a rule I often use. I mean to change
the size of dst object some where outside of the decode function.
3. Is it possible to create other ways to generate a logstring based on the
std::string content?

Thanks,
Tom


2009/11/13 Zhou Tao <zhoutao109@gmail.com>

> Hi all,
>
> I am using log4cxx on win32 platform and  build the log4cxx with MT option(
> Runtime Library) within MS visual Studio 2005. The project default setting
> is MD. All APR, APR-UTIL and LOG4CXX projects are set to be MT mode.
>
> After the build, I get a crash in the LOG4CXX_DECODE_CHAR macro. The code
> is very simple, looks like the below,
>
> void testFun()
> {
> std::string src = "log4cxx-string-testing";
> LOG4CXX_DECODE_CHAR(dest, src);
> }
>
> The crash happens when leave the function when trying to delete the
> allocated memory. If the length of the src string is less than 7, it works.
>
> Is this a problem?
>
> --
> Thanks and Regards,
> Tom
>



-- 
Thanks and Regards,
Tom

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