[boost] [thread] age-old, fatal, trivial-to-fix bug

From: Ulrich Eckhardt (doomster_at_[hidden])
Date: 2007-02-10 03:35:18

(Sorry for the flashy topic, but I reported the bug already ages ago and I'm 
slightly annoyed that it is still present. But hey, at least I could restrain 
myself from using multiple exclamation marks.)

Hi!

If you compile libs/thread/src/exception.cpp, some compilers will warn you 
about an unused variable (the argument to system_message()) when not 
compiling for win32. Firstly, the fact that it doesn't use this variable but 
uses errno directly to format a string is already broken, after all I 
explicitly requested it to format a string for the given errorcode, not one 
that happens to be in errno at that time (well, you could argue that that is 
intended, after all the function is undocumented, but then you'd have to do 
the same with win32 and use GetLastError() there). 

Secondly, look at the way that function is used. It is used in 
thread_exception::message() to format a std::string temporary and then return 
the result of c_str() from a function! This returns a reference to a 
temporary and the returned pointer can never be used! It can't work, simple 
as that, it's broken and as far as I'm concerned it is even obviously so.

Solution: remove thread_exception::message(), no sane code could ever have 
depended on that function anyway. Remove system_message() all along, it is 
unused then. There is a slew of other code that is intended to access 
strerror() (for POSIX) or FormatMessage() (for win32) in a portable way, 
which is then also unused (of course, after all system_message() is a wrapper 
around those and with it unused, those can go, too).

Please, please, please fix this! I have attached the patch for current CVS but 
the same is already present in at least 1.33 and probably older versions, 
too.

thank you

Uli