October 2004 - Boost - lists.preview.boost.org

can emacs cc-mode be made to do boost-style preprocessor indents?
by Jonathan Graehl 01 Oct '04

01 Oct '04

The Boost style of nested indenting for preprocessor directives is nice. I'm using cc-mode for emacs (the sourceforge version), and it doesn't seem to directly support this: #if 1 # if 2 # define A 1 # else # endif #endif I found this cc-mode mailing list discussion that confirmed the lack of support: http://sourceforge.net/mailarchive/forum.php?thread_id=5382045&forum_id=6827 Anyone already got some working elisp for preprocessor autoindent?

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Portable test_and_set, please...
by no_carrier 01 Oct '04

01 Oct '04

Hi all, I see some atomic operations in atomic_count.hpp (usable only by the atomic_count class unfortunately, and not directly) for incrementing and decrementing, but the most important atomic operation seems to be missing: the test_and_set. Without that one it's not possible to create lockfree algorithms in MT. Also, atomic incrementing, decrementing etc. can be performed having the test_and_set but not vice versa. Would anybody please make a wrapper for that? On Windows it's the InterlockedCompareExchange, on Gcc and Linux I think they are called __test_and_set and atomic_test_and_set respectively. I don't know if they would better go in the Boost.Threads or in the atomic_something header files... Thanks

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[Signals] slot/trackable object disconnection question
by Dave Deakins 01 Oct '04

01 Oct '04

I have a question about the disconnection of slots in the signals library. I couldn't find any information about it in previous message threads, but if I missed one you guys can just direct me to the appropriate discussion. In my project I have a serial port communications queue that allows various other objects to transmit a command over the serial port and then have the response routed to a designated callback function. Each command request can specify a different response callback function and often the object posting the command will ask the queue to pass the response data back to one of its member functions for interpretation. I use the automated connection management feature of signals to insure that the response member function is not called if its target object is destroyed before the serial port response is received. This queue typically handles about 10-15 command/response transactions per second and I noticed that, after about 15-20 hours of continuous operation, the system began to run low on available memory. I spent a fair amount of time trying to track down the source of the excessive memory usage and it appeared that it was coming from the trackable object base class. Each time a command is added to the communications queue, a new queue entry is created and we connect the response handling function to the signal in this queue entry. If I understand correctly, signal's connect function will create a temporary slot object to adapt the boost::bind(&AClass::ResponseFunction, pAClass, _1, _2) object that is passed to it. When this temporary slot is created, it uses visit_each to enumerate the bound trackable objects and then uses trackable::signal_connected(...) to have each bound trackable object save a 'controlling' connection to the slot in its connected_signals list. So if any of the bound trackable objects are destroyed, the 'controlling' connection will deactivate the slot and tell all of the bound trackable objects used by the slot that they can erase their connections to this slot. So my question is this: When a slot object (not a signal object) is destroyed, what tells the trackable objects that are used by the slot that they can release their connection to this slot? Signal objects make the connections in their internal slot map 'controlling' so these connections would do the clean up when the signal is destroyed. As mentioned above, trackable objects also make the connections in their internal connected_signals list 'controlling' to enable deactivation and clean up of standalone slots or slots connected to signals when the trackable object is destroyed. But the watch_bound_objects connection in the slot object is not 'controlling' (as far as I can tell) and thus a slot does not seem to have any way to indicate to the bound objects that this connection needs to be cleaned up if the slot is destroyed. The following program roughly illustrates the behaviour I see in my application: #include "boost\bind.hpp" #include "boost\signals.hpp" class CommunicatingObject : public boost::signals::trackable { public: void ProcessResponse() {} }; int main(int argc, char* argv[]) { CommunicatingObject Obj; while (true) { boost::signal0<void> NewResponseData; NewResponseData.connect( boost::bind(&CommunicatingObject::ProcessResponse, &Obj) ); NewResponseData(); } return 0; } Obj would represent the object making a request on the queue and NewResponseData would represent the signal contained in the queue entry. When I run this test program on my system, the system runs out of memory in fairly short order. I have the same memory draining situation if the while(true) loop is changed to the simpler case of: while (true) { boost::signal0<void>::slot_type( boost::bind(&CommunicatingObject::ProcessResponse, &Obj) ); } Can someone please confirm if this behavior happens on other systems or if maybe there is some pecularity with my system/compiler? If this situation is not peculiar to my system, should there be a: watch_bound_objects.set_controlling(); statement at the very end of the slot_base::create_connection() procedure (after the safe_connection.release() statement) in slot.cpp? Thanks in advance for your help, -Dave

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Re: [boost] [Random] GCC 2.95.3 regressions
by Michael Stevens 01 Oct '04

01 Oct '04

> Aleksey Gurtovoy writes: > > > > Given that the code compiles with the latests versions of the > > compiler, the following (from http://tinyurl.com/58lll) is most likely > > to be a compiler bug, but since the test used to pass some time ago, I > > was wondering if anyone is interested in making it work again or simply > > commenting on it before I mark it green: > > [snip errors] > > OK, seems like nobody is interested in these, marked up as expected. I took a quick look. It seems like gcc-2.95 has namespace problems when BOOST_USING_STD_MIN/MAX Since Random never worked on systems without min/max in std I have simplified and use std::min/max instead. This fixes gcc-2.95 and should not regress on any of the good compilers. If this looks good in the tests tomorrow I will remove the failure markup. Michael

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use of strcpy, strcat, etc in Boost libraries
by Reece Dunn 01 Oct '04

01 Oct '04

Hi All, In my post on the "vc8.0 toolset (bjam)" thread, I commented that VC8 also warns when using the str[n]xxx APIs, because MS declares them deprecated. There are several issues here: [1] How does this impact Boost code that uses the <cstring> API? Especially since they deprecate the strn variations as well, which are safer, and considering that the "safe" versions are not yet a part of the standard. Would it be possible to put this in the Boost <cstring> header? I.e. using the safe versions for VC8 and using the C9x API for the other compilers/libraries. [2] Does this affect the Intel compiler using the Dinkumware libraries because Intel does not like how the library declares items deprecated. (This is already an issue using the <locale> header and <hash_xxx> extensions). [3] What are the wider security issues of using strcpy, etc in Boost code? The libraries should use the strnxxx variants for better protection against buffer overrun attacks, but I found several instances where strcpy was used (I haven't checked for strcat, strcmp and others) instead of strncpy: boost/regex/v4/regex_cstring.hpp (104): use of strcpy [via re_strcpy] libs/regex -- various files using strcpy libs/serialization/test/test_tools.hpp (69): use of strcpy [via STRCPY] libs/smart_ptr/test/smart_ptr_test.cpp (139/223): use of strcpy tools/build/jam_src -- execnt.c; regexp.c; variable.c [4] Doing this, I found that regex was using re_strcpy as a workaround for Borland using strxxx as macros when using intrinsics. Serialization uses STRCPY for a similar workaround, and my fixed_string library uses the following: # if defined(__BORLANDC__) && defined(strcpy) // replace Borland instrinsic string function # undef strcpy inline char * strcpy( char * dest, const char * src ) { return( __strcpy__( dest, src )); } # endif So: should the workarounds be placed in <cstring> and affected libraries use the Boost version. NOTE: I suggested telling Boost.Build to disable the deprecated API warning for the upcoming release and then address these issues for the next (1.33) release. Thoughts? Comments? Regards, Reece

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