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Re: [Boost-Users] lexical_cast bug.
by Terje Slettebø 23 Feb '03

23 Feb '03

>From: "Eduardo Chao" <efchao(a)hotmail.com> > I am a new suscriber to the list. > I want to report what I consider a bug in lexical_cast conversion template. > First, I wanted to use it to convert things to std::string (Target). > It throws a bad_lexical_cast_exception when I pass an empty std::string object (one > that is default-constructed or constructed with "") as the Source argument. > It throws it because the condition (interpreter >> result ) evaluates to > false. Yes, this is a bug in the current version, see (http://www.boost.org/libs/conversion/lexical_cast.htm#future) There's a proposition which fixes this and other problems here (http://groups.yahoo.com/group/boost/files/lexical_cast_proposition/lexical_ cast_proposition.zip). It's scheduled to be reviewed by the author, Kevlin Henney, or Björn Karlsson (Boost's maintenance wizard), before Boost release 1.30. If they find it ok, a notice will also be posted at the Boost list, so that others may give feedback before the release, as well. > My solution was to specialize the function template this way: > > template<> lexical_cast<std::string>(const std::string &str) > { > return str; > } The proposition handles it in a similar way. However, it's not possible to partially specialise function templates (e.g. to handle all T -> std::basic_string conversions), so function template overloading is used, instead. This is because it needs to handle conversion from any type to std::basic_string, as there may be other types which output empty strings or whitespace, as well. > but it is not so general to support const std::string or const std::string& > as Target type or perhaps std::string or const std::string etc as Source. > Correct me if I am wrong, so I learn from you more experienced Boost (and then C++) users. No, you're right. However, it's only necessary to handle T -> std::basic_string (not cv-qualification or reference) in this case, because: lexical_cast<std::string>(...); // Ok lexical_cast<const std::string>(...); // Error, can't write to a const string lexical_cast<const std::string &>(...); // Error, can't return a reference to the result (it would then return a dangling reference, as the result would be a temporary) lexical_cast<std::string>(const_cast<const std::string>(...)); // Ok, top-level cv-qualifiers are ignored when matching the call Regards, Terje

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random/histogram.cpp
by agiatojon <JonAgiato＠nyc.rr.com> 23 Feb '03

23 Feb '03

Hello all, I have been unable to successfully compile histogram.cpp in the random library folder, version 1_29_0, using Visual Studio.NET. I obtain the following errors: c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(49): warning C4267: 'argument' : conversion from 'size_t' to 'std::streamsize', possible loss of data c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(101): error C2065: 'gen' : undeclared identifier c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type It appears to me that all of these messages will go away when the second one, c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base', is corrected. Any assistance is greatly apprechiated! Thank you. Jon Agiato JonAgiato(a)nyc.rr.com

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[BGL] Using external edge properties
by yg-boost-users＠m.gmane.org 22 Feb '03

22 Feb '03

I have a graph which might change during it's lifetime. I want to attach external properties to this graph. Now, it seems like that in order to be able to attach external properties, I need to have an internal property with edge indices, ie that enumerates the edges. These indices need to be continuous as I gather, since they are used to index for instance a vector of num_edges() elements. Does this mean that I have to re-enumerate all edges if I remove one? This seems to me very cumbersome and also time consuming if the graph is large and changes a lot. Is there another way? Björn Lindberg

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bug in shared_ptr
by Simone Finotti 22 Feb '03

22 Feb '03

hi all, I don't know if this is the right place to report bug, if it's not please forgive me. I was trying to use boost/shared_ptr.hpp class, so I defined BOOST_NO_EXCEPTIONS because my compiler doesn't support C++ exceptions, but I receive this error: ..\..\boost_1_29_0\boost/detail/shared_count.hpp(122) : error C2039: 'use_count_is_zero' : is not a member of 'boost' ..\..\boost_1_29_0\boost/detail/shared_count.hpp(122) : error C2065: 'use_count_is_zero' : undeclared identifier in detail, here's an excerpt from shared_count.hpp, where the compiler gives the error: void add_ref() { #ifdef BOOST_HAS_THREADS mutex_type::scoped_lock lock(mtx_); #endif if(use_count_ == 0 && weak_count_ != 0) boost::throw_exception(boost::use_count_is_zero()); ++use_count_; ++weak_count_; } use_count_is_zero is not defined because it's defined, in the same file, as: #ifndef BOOST_NO_EXCEPTIONS class use_count_is_zero: public std::exception { public: virtual char const * what() const throw() { return "boost::use_count_is_zero"; } }; #endif is there a way to make it work? -- Simone

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Can one "nest" regular expressions ?
by yg-boost-users＠m.gmane.org 22 Feb '03

22 Feb '03

Hello folks, I believe my question applies to regular expression libraries generally and not just to regexp++. I want to know if it is possible to refer to or use one regular expression within another. What I wish to do is parse a string of html code for img tags, and if they have the clause ALT="whatever" replace the whole image tag with 'whatever'. So I decided to make regular expression for an image tag which had an ALT part, and have a sub-match on the contents of quoted part of the ALT. (I broke this up a bit, explaining what each part is for . . .) This will match img tags: static const boost::regex find_imgs(" <\\s*img Matches <, 0 or many whitespace, IMG \\s+src\\s* Matches 1 or more whitespace, SRC, 0 or many whitespace =\\s* Matches = followed by 0 or more whitespace \"\\s* Matches " followed by 0 or more whitespace ([^\"]*) Matches any number of characters that are not " ([^>]*>) Matches any number of chars that not >, followed by a > ", boost::regbase::normal | boost::regbase::icase); Ok, so now look at this one. I'm trying to do the same as above except I want to sub-match the quoted part of the alt part so I can use it. I can't do "anything except the word 'alt'" because it will interpret the [^(alt)] as "anything except 'a', 'l', or 't'". static const boost::regex find_imgs_with_alt(" <\\s*img Matches <, 0 or many whitespace, IMG \\s+src\\s* Matches 1 or more whitespace, SRC, 0 or many whitespace =\\s* Matches = followed by 0 or more whitespace \"\\s* Matches " followed by 0 or more whitespace [^\"]* Matches any number of chars not " \\s+ Matches 1 or more whitespace [^alt]* I would like match anything except the word ALT, but the regexp stuff interprets this as anything but 'a', 'l', or 't' alt\\s*= Matches ALT, 0 or whitespace, = \"(^\")\" Matches ", anything except a " as a group that I can reference, then another " [^>]*> Matches any number of chars not >, followed by a > ", boost::regbase::normal | boost::regbase::icase); So what I want to do is make another regular expression which matches "alt", and in the part that says [^alt]* do instead something like [^@alt]* where '@' would indicate that 'alt' was the name of another regular expression, such as static const boost::regex alt("alt", boost::regbase::normal | boost::regbase::icase); I can see how to do what I want to do without this; I would get the whole IMG tag and do a separate regexp_search on the match. But it seems to make it so much easier if it were possible, especially leaving me with fewer lines of regular expression code to have bugs in. If this is possible I'd like to know. Thanks in advance, and I'll post the regular expressions I end up using here if anyone might find them of use. --Rob

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lexical_cast bug.
by Eduardo Chao 22 Feb '03

22 Feb '03

Hello, I am a new suscriber to the list. I want to report what I consider a bug in lexical_cast conversion template. First, I wanted to use it to convert things to std::string (Target). It throws a bad_lexical_cast_exception when I pass an empty std::string object (one that is default-constructed or constructed with "") as the Source argument. It throws it because the condition (interpreter >> result ) evaluates to false. My solution was to specialize the function template this way: template<> lexical_cast<std::string>(const std::string &str) { return str; } but it is not so general to support const std::string or const std::string& as Target type or perhaps std::string or const std::string etc as Source. Correct me if I am wrong, so I learn from you more experienced Boost (and then C++) users. That's all for now. Thanks in advance. Eduardo Chao. [Non-text portions of this message have been removed]

1 0

Testing Boost:threads on windows w/ cygwin/gcc help
by sam <samijackson＠yahoo.com> 21 Feb '03

21 Feb '03

Howdy, I have cygwin running on a WinXP box and am trying to get the threads up and running. I built the Boost.Threads and things look good. Then I try: "bjam -sTOOLS=gcc test" from the /lib/thread/test directory and the test fails with: <build> ...found 1203 targets... ...using 1 temp target... ...updating 181 targets... ...using <libs!thread!test/test_thread.test/gcc/debug/runtime-link-static/threa ding-multi>test_thread.run... succeeded-test-file ../../../libs/thread/test/bin/test_thread.test/gcc/debug/runtime-link- static/threading-multi/test_thread.test Syntax error: "fi" unexpected (expecting "then") <chomp/> echo "*" echo "***************** failed above test: test_thread ********************" echo "*" </build> My question is, how do I correctly get Boost to use either native or pthreads and pass the tests above? I've checked the FAQs, Googled and all that, but can't seem to find an answer. I'm sure it's easy, but can't get it right. thanks Sam

3 5

boost::mutex, Borland C++Bulder 6 and CodeGuard
by Russell Hind 21 Feb '03

21 Feb '03

I have been running into CodeGuard problems using boost 1.29.0 with BorlandC++Builder 6Pro update 2 and CodeGuard. The test project is a console app, multi-threading but no vcl (don't know if the VCL enabled affects it or not). The code is #include <boost/thread/mutex.hpp> int main(int argc, char* argv[]) { boost::mutex m; return 0; } I get a resource type mismatch on exit which is down to the mutes. I have linked directly with the source and found where the problem lies. It could be down to 2 places: a) boost allocates the mutex (mutex.cpp line 39) using the nowthrow operator new m_mutex = reinterpret_cast<void*>(new(std::nothrow) CRITICAL_SECTION); and then deletes it using the standard delete (mutex.cpp line 48) delete reinterpret_cast<LPCRITICAL_SECTION>(m_mutex); This causes slight problems as codeguard treats allocations from new and malloc differently to check you free the memory correctly. nothrow new uses malloc, so a standard delete is the incorrect way to free the mutex here from CodeGuards point of view. I have changed the delete to operator delete (reinterpret_cast<LPCRITICAL_SECTION>(m_mutex), std::nothrow); which calls the nothrow version of delete. Unfortunately, the next part of the problem: b) For some reason, the mutex is using the roguewave stl new.h which defines the nothrow operators as such (oldstl\new.h line 143) inline void * _RTLENTRY operator new (size_t size, const std::nothrow_t &nt) { size = size ? size : 1; return malloc(size); } (oldstl\new.h line 152) inline void _RTLENTRY operator delete (void *v, const std::nothrow_t &nt) { ::operator delete (v); // The standard operator doesn't throw any exceptions } Here, there is a conflict in the allocation and deallocation. changing line 154 to free(v); along with the change to mutex to use the nothrow version of delete fixes it so codeguard can be used. Looking in the stlport new, it forces us to use RogueWave's new because of these lines in stlport\new line 49 # if !defined (_STLP_NO_NEW_NEW_HEADER) # include _STLP_NATIVE_CPP_RUNTIME_HEADER(new) # else # include <new.h> # endif which makes it include roguewaves version of new. So C++Builder 6 is still reliant on roguewave stl even when set to use STLPort. Possible solutions are a) Make boost::thread use nothrow version of delete but this requires a fix in the borland/rogue wave header for the delete to make it use free. or b) mutex could use malloc and free directly for borland. Which would people prefer or can anyone think of another solution? Cheers Russell

2 1

Boost::Threads condition variable on Win32 and IO completion routines
by Russell Hind 21 Feb '03

21 Feb '03

The start of the do_wait() method of a boost::condition (in 1.29.0) for Win32 looks like this void condition::do_wait() { int res = 0; res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_queue), INFINITE); assert(res == WAIT_OBJECT_0); This waits indefinitely until m_queue is signalled. Would it be safe to change this so the thread is alertable for IO completion routines? Something like int res = 0; while ((res = WaitForSingleObjectEx(reinterpret_cast<HANDLE>(m_queue), INFINITE, true)) == WAIT_IO_COMPLETION) { } assert (res == WAIT_OBJECT_0); We make fairly heavy use of Waitable Timers in our statemachines. The completion routine for a timer is called back in the context of the thread that started it, when the thread is alertable. WaitForSingleObject doesn't allow the thread to be alertable. We currently use this in our own thread (with Windows events) but are looking to update the message queue code and thread code to use boost. With out this change, it would currently break a lot of code if we were to use condition variables. Thanks Russell

3 2

Regex++
by Yutaka Emura 21 Feb '03

21 Feb '03

Hi John "(?!foo)bar" matches "bar" in the last three lines of the following: foobar ??bar barfoo bar?? bar Why doesn't it match "bar" in all the lines? Yutaka Emura --------------- > I am using RegEx in Boost v1.29.0. > (?= ) and (?! ) expressions do not seem to work at a certain > condition. > > In the following example, "(?=a)b" should match "b" in "xyzabcdefg", > but does not. Which is correct: (?=a) is a forward lookahead *possitive* assertion, so (?=a)b can never match anything since the next character can't be both an 'a' and a 'b' at the same time! > Similarly, "(?!a)b" should not match "b" in "xyzabcdefg" but it does. It should match: (?!a) will match anything except 'a' so (?!a)b will match the next 'b' that it finds.

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