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  • iPad receiving memory warning with low memory use

    - by Fer
    I have an UIWebKit with a HTML, this HTML have several images and text, but just displaying it gives me the memory warning. So I did some tests: The same HTML with different images, fullsize, and after the same images but reduced 50% from it's original size, for the 50% reduced images, I went to preview and reduced all images in 50% The surprising part is the 50% test, you can see that even with 16 images, the memory peak is 4.90MB. That's really surprising. Notice that these values are not always the same, they change but there's not a huge difference between the tests. In the 50% issue, in the 8 and 16 images, although the memory is low, sometimes a memory warning appears, but the performance enhance is noticeable compared to the full size images standing still = memory after scrolling all article 1 Image = [standing still 5MB] [rotating 5.6MB] 2 Images = [standing still 6.99MB] [rotating 7.7MB] 3 Images = [standing still 9.04MB] [rotating 10.9MB] 4 Images = [standing still 10.89MB] [rotating 13.20MB] 8 Images = [standing still 23.14MB] [rotating 25.20MB] (sometimes crashes) 16 Images = [standing still 27.14MB and app crashes] 50% 1 Image = [standing still 3.2MB] [rotating 3.67MB] 2 Image = [standing still 3.2MB] [rotating 3.70MB] 3 Image = [standing still 3.3MB] [rotating 3.79MB] 4 Image = [standing still 3.3MB] [rotating 3.80MB] 8 Images = [standing still 4.29MB] [rotating 4,63MB] (sometimes crashes) 16 Images = [standing still 4.79MB] [rotating 4,90MB] (sometimes crashes) My question is: The app sometimes crashed with 16 small images. Why? The memory was much lower. What is the limit of memory use? These numbers are helpful if you also tell us the maximum. But, the maximum seemed different with the 50% size images. 13.2MB works for large images and 3.8 for small images. Anything higher sometimes crashes. That makes no sense.

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  • PHP - warning - Undefined property: stdClass - fix?

    - by Phill Pafford
    I get this warning in my error logs and wanted to know how to correct this issues in my code. Warning: PHP Notice: Undefined property: stdClass::$records in script.php on line 440 Some Code: // Parse object to get account id's // The response doesn't have the records attribute sometimes. $role_arr = getRole($response->records); // Line 440 Response if records exists stdClass Object ( [done] => 1 [queryLocator] => [records] => Array ( [0] => stdClass Object ( [type] => User [Id] => [any] => stdClass Object ( [type] => My Role [Id] => [any] => <sf:Name>My Name</sf:Name> ) ) ) [size] => 1 ) Response if records does not exist stdClass Object ( [done] => 1 [queryLocator] => [size] => 0 ) I was thinking something like array_key_exists() functionality but for objects, anything? or am I going about this the wrong way?

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  • Disable Eclipse warning about generated html?

    - by Chadwick
    When developing Flex projects, Eclipse gives warnings about the default index.html file generated by Flex Builder. The file is in the 'target' folder (or "generated artifacts" folder. Yes, I'm also using Maven). Can I eliminate or disable this warning? The code which generates the warning is below, though I would definitely prefer not changing the html - as I say this is the template suggested by Adobe. Eclipse warns of "Undefined attribute name (xxx)" for scroll on the body tag, and most of the embed attributes. There is no DOCTYPE declaration in the html file. <html lang="en"> ... <body scroll="no"> ... <embed src="myswf.swf" quality="high" bgcolor="#869ca7" width="100%" height="100%" name="myswf-flex" align="middle" play="true" loop="false" quality="high" allowScriptAccess="sameDomain" type="application/x-shockwave-flash" pluginspage="http://www.adobe.com/go/getflashplayer"> </embed> ...

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  • PHP Cookie Warning...

    - by Nano HE
    Hi,I am new to PHP, I practised PHP setcookie() just now and failed. http://localhost/test/index.php <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title></title> </head> <body> <?php $value = 'something from somewhere'; setcookie("TestCookie", $value); ?> </body> </html> http://localhost/test/view.php <?php // I plan to view the cookie value via view.php echo $_COOKIE["TestCookie"]; ?> But I failed to run index.php, IE warning like this. Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\test\index.php:9) in C:\xampp\htdocs\test\index.php on line 12 I enabled my IE 6 cookie no doubt. Is there anything wrong on my procedure above? Thank you. WinXP OS and XAMPP 1.7.3 used.

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  • Warning: cast increases required alignment

    - by dash-tom-bang
    I'm recently working on this platform for which a legacy codebase issues a large number of "cast increases required alignment to N" warnings, where N is the size of the target of the cast. struct Message { int32_t id; int32_t type; int8_t data[16]; }; int32_t GetMessageInt(const Message& m) { return *reinterpret_cast<int32_t*>(&data[0]); } Hopefully it's obvious that a "real" implementation would be a bit more complex, but the basic point is that I've got data coming from somewhere, I know that it's aligned (because I need the id and type to be aligned), and yet I get the message that the cast is increasing the alignment, in the example case, to 4. Now I know that I can suppress the warning with an argument to the compiler, and I know that I can cast the bit inside the parentheses to void* first, but I don't really want to go through every bit of code that needs this sort of manipulation (there's a lot because we load a lot of data off of disk, and that data comes in as char buffers so that we can easily pointer-advance), but can anyone give me any other thoughts on this problem? I mean, to me it seems like such an important and common option that you wouldn't want to warn, and if there is actually the possibility of doing it wrong then suppressing the warning isn't going to help. Finally, can't the compiler know as I do how the object in question is actually aligned in the structure, so it should be able to not worry about the alignment on that particular object unless it got bumped a byte or two?

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  • Visutal Studio Warning "Content is not allowed" in ASP.NET project

    - by pstar
    Hi, I am just started working as a programmer last month, so there will be plenty of newbie question come from me, stay tuned... I am now working on modify the provided template (from DevExpress) to create new web form using ASP.NET 2.0 on Visual Studio 2008. While the functionality of that web form is there, I am in the process of get rid of ninety something warning message, most of them come from the provided template. One of them puzzled me for a while is this one: "Warning 75 Content is not allowed between the opening and closing tags for element 'ClientSideEvents'." And here is the code: <dxe:ASPxListBox id="edtMultiResource" runat="server" width="100%" SelectionMode="CheckColumn" DataSource='<%# ResourceDataSource %>' Border-BorderWidth="0"> <ClientSideEvents SelectedIndexChanged="function(s, e) { var resourceNames = new Array(); var items = s.GetSelectedItems(); var count = items.length; if (count > 0) { for(var i=0; i<count; i++) _aspxArrayPush(resourceNames, items[i].text); } else _aspxArrayPush(resourceNames, ddResource.cp_Caption_ResourceNone); ddResource.SetValue(resourceNames.join(', ')); }"></ClientSideEvents> </dxe:ASPxListBox> I couldn't see anything wrong with the code myself, so please help me out here.

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  • modified closure warning in ReSharper

    - by Sarah Vessels
    I was hoping someone could explain to me what bad thing could happen in this code, which causes ReSharper to give an 'Access to modified closure' warning: bool result = true; foreach (string key in keys.TakeWhile(key => result)) { result = result && ContainsKey(key); } return result; Even if the code above seems safe, what bad things could happen in other 'modified closure' instances? I often see this warning as a result of using LINQ queries, and I tend to ignore it because I don't know what could go wrong. ReSharper tries to fix the problem by making a second variable that seems pointless to me, e.g. it changes the foreach line above to: bool result1 = result; foreach (string key in keys.TakeWhile(key => result1)) Update: on a side note, apparently that whole chunk of code can be converted to the following statement, which causes no modified closure warnings: return keys.Aggregate( true, (current, key) => current && ContainsKey(key) );

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  • Warning: Trim expects

    - by user1257518
    I'm getting this warning Warning: trim() expects parameter 1 to be string, array given in .. which is my trim line. The full code is functioned to send an error when fields are empty. However, this error appears saying every field is empty, but only the 'native' field is meant to be required so thats my 2nd problem. Thanks for any help! session_start(); $err = array(); $user_id = intval($_SESSION['user_id']); // otherwise if (isset($_POST['doLanguage'])) { $link = mysql_connect(DB_HOST, DB_USER, DB_PASS) or die("Couldn't make connection."); // check if current user is banned $the_query = sprintf("SELECT COUNT(*) FROM users WHERE `banned` = '0' AND `id` = '%d'", $user_id); $result = mysql_query($the_query, $link); $user_check = mysql_num_rows($result); // user is ok if ($user_check > 0) { // check for empty fields foreach ($_POST as $key => $val) { $value = trim($val); if (empty($value)) { $err[] = "ERROR - $key is required"; } } // no errors if(empty($err)) { for($i = 0; $i < count($_POST["other"]); $i++) $native = mysql_real_escape_string($_POST['native'][$i]); $other = mysql_real_escape_string($_POST['other'][$i]); $other_list = mysql_real_escape_string($_POST['other_list'][$i]); $other_read = mysql_real_escape_string($_POST['other_read'][$i]); $other_spokint = mysql_real_escape_string($_POST['other_spokint'][$i]); $other_spokprod = mysql_real_escape_string($_POST['other_spokprod'][$i]); $other_writ = mysql_real_escape_string($_POST['other_writ'][$i]); // insert into the database $the_query = sprintf("INSERT INTO `language` (`user_id`,`native`,`other`,`other_list`,`other_read`, `other_spokint` ,`other_spokprod`,`other_writ` ) VALUES ('%d','%s','%s','%s','%s','%s','%s','%s')", $user_id,$native,$other,$other_list,$other_read, $other_spokint,$other_spokprod,$other_writ); // query is ok? if (mysql_query($the_query, $link) ){ // redirect to user profile header('Location: myaccount.php?id=' . $user_id); } } } }

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  • Linking to MSVC DLL from MinGW

    - by IndigoFire
    I'm trying to link the LizardTech GeoExpress DSDK into my own application. I use gcc so that we can compile on for platforms. On Linux and Mac this works easily: they provide a static library (libltidsdk.a) and headers and all that we have to do is use them. Compiling for windows isn't so easy. They've built the library using Microsoft Visual Studio, and we use MinGW. I've read the MinGW FAQ, and I'm running into the problems below. The library is all C++, so my first question: is this even possible? Just linking against the dll as provided yields "undefined reference" errors for all of the C++ calls (constructors, desctructors, methods, etc). Based on the MinGW Wiki: http://www.mingw.org/wiki/MSVC%5Fand%5FMinGW%5FDLLs I should be able to use the utility reimp to convert a .lib into something useable. I've tried all of the .lib files provided by LizardTech, and they all give "invalid or corrupt import library". I've tried both version 0.4 and 0.3 of the reimp utility. Using the second method described in the wiki, I've run pexport and dlltool over the dll to get a .a archive, but that produces the same undefined references. BTW: I have read the discussion below. It left some ambiguity as to whether this is possible, and given the MinGW Wiki page it seems like this should be doable. If it is impossible, that's all I need to know. If it can be done, I'd like to know how I can get this to happen. stackoverflow.com/questions/1796209/how-to-link-to-vs2008-generated-libs-from-g Thanks!

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  • What is weird about wrapping setjmp and longjmp?

    - by Max
    Hello. I am using setjmp and longjmp for the first time, and I ran across an issue that comes about when I wrap setjmp and longjmp. I boiled the code down to the following example: #include <stdio.h> #include <setjmp.h> jmp_buf jb; int mywrap_save() { int i = setjmp(jb); return i; } int mywrap_call() { longjmp(jb, 1); printf("this shouldn't appear\n"); } void example_wrap() { if (mywrap_save() == 0){ printf("wrap: try block\n"); mywrap_call(); } else { printf("wrap: catch block\n"); } } void example_non_wrap() { if (setjmp(jb) == 0){ printf("non_wrap: try block\n"); longjmp(jb, 1); } else { printf("non_wrap: catch block\n"); } } int main() { example_wrap(); example_non_wrap(); } Initially I thought example_wrap() and example_non_wrap() would behave the same. However, the result of running the program (GCC 4.4, Linux): wrap: try block non_wrap: try block non_wrap: catch block If I trace the program in gdb, I see that even though mywrap_save() returns 1, the else branch after returning is oddly ignored. Can anyone explain what is going on?

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  • C malloc assertion help

    - by Chris
    I am implementing a divide and conquer polynomial algorithm so i can bench it against an opencl implementation, but i can't seem to get malloc to work. When I run the program it allocates a bunch of stuff, checks some things, then sends the size/2 to the algorithm. Then when I hit the malloc line again it spits out this: malloc.c:3096: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)-bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) = (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)-size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed. Aborted The line in question is: int *out, .....other vars....; out = (int *)malloc(sizeof(int) * size * 2); I have checked size with fprintf and it is a positive int (usually 50 at that point). I have tried calling malloc with a plain number as well and i still get the error. I'm just stumped at what's going on, and nothing from google that I have found so far has been too helpful. Any ideas what's going on? I'm trying to figure out how to compile a newer GCC in case it's a compiler error, but i really doubt it.

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  • Compile and optimize for different target architectures

    - by Peter Smit
    Summary: I want to take advantage of compiler optimizations and processor instruction sets, but still have a portable application (running on different processors). Normally I could indeed compile 5 times and let the user choose the right one to run. My question is: how can I can automate this, so that the processor is detected at runtime and the right executable is executed without the user having to chose it? I have an application with a lot of low level math calculations. These calculations will typically run for a long time. I would like to take advantage of as much optimization as possible, preferably also of (not always supported) instruction sets. On the other hand I would like my application to be portable and easy to use (so I would not like to compile 5 different versions and let the user choose). Is there a possibility to compile 5 different versions of my code and run dynamically the most optimized version that's possible at execution time? With 5 different versions I mean with different instruction sets and different optimizations for processors. I don't care about the size of the application. At this moment I'm using gcc on Linux (my code is in C++), but I'm also interested in this for the Intel compiler and for the MinGW compiler for compilation to Windows. The executable doesn't have to be able to run on different OS'es, but ideally there would be something possible with automatically selecting 32 bit and 64 bit as well. Edit: Please give clear pointers how to do it, preferably with small code examples or links to explanations. From my point of view I need a super generic solution, which is applicable on any random C++ project I have later. Edit I assigned the bounty to ShuggyCoUk, he had a great number of pointers to look out for. I would have liked to split it between multiple answers but that is not possible. I'm not having this implemented yet, so the question is still 'open'! Please, still add and/or improve answers, even though there is no bounty to be given anymore. Thanks everybody!

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  • Binder and variadic template ends up in a segmentation fault

    - by phlipsy
    I wrote the following program #include <iostream> template<typename C, typename Res, typename... Args> class bind_class_t { private: Res (C::*f)(Args...); C *c; public: bind_class_t(Res (C::*f)(Args...), C* c) : f(f), c(c) { } Res operator() (Args... args) { return (c->*f)(args...); } }; template<typename C, typename Res, typename... Args> bind_class_t<C, Res, Args...> bind_class(Res (C::*f)(Args...), C* c) { return bind_class<C, Res, Args...>(f, c); } class test { public: int add(int x, int y) { return x + y; } }; int main() { test t; // bind_class_t<test, int, int, int> b(&test::add, &t); bind_class_t<test, int, int, int> b = bind_class(&test::add, &t); std::cout << b(1, 2) << std::endl; return 0; } compiled it with gcc 4.3.3 and got a segmentation fault. After spending some time with gdb and this program it seems to me that the addresses of the function and the class are mixed up and a call of the data address of the class isn't allowed. Moreover if I use the commented line instead everything works fine. Can anyone else reproduce this behavior and/or explain me what's going wrong here?

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  • Unable to find reference to std library math function inside library

    - by Alex Marshall
    Hello, I've got several programs that use shared libraries. Those shared libraries in turn use various standard C libraries. ie Program A and Program B both use Shared Library S. Shared Library S uses std C math. I want to be able to statically link Shared Library S against the standard library, and then statically link Programs A and B against S so that I don't have to be dragging around the library files, because these programs are going to be running on an embedded system running BusyBox 0.61. However, when I try to statically link the programs against Shared Library S, I get an error message from GCC stating : ../lib/libgainscalecalc.a(gainscalecalc.): In function 'float2gs': [path to my C file].c:73: undefined reference to 'log' Can somebody please help me out ? The make commands I'm using are below : CFLAGS += -Wall -g -W INCFLAGS = -I$(CROSS_INCLUDE)/usr/include LIBFLAGS += -L$(CROSS_LIB)/usr/lib -lm gainscalecalc_static.o: gainscalecalc.c $(CC) $(CFLAGS) -c $< -I. $(INCFLAGS) -o $@ gainscalecalc_dynamic.o: gainscalecalc.c $(CC) $(CFLAGS) -fPIC -c $< -o $@ all: staticlib dynamiclib static_driver dynamic_driver clean: $(RM) *.o *.a *.so *~ driver core $(OBJDIR) static_driver: driver.c staticlib $(CC) $(CFLAGS) -static driver.c $(INCFLAGS) $(LIBFLAGS) -I. -L. -lgainscalecalc -o $@ dynamic_driver: driver.c dynamiclib $(CC) $(CFLAGS) driver.c -o $@ -L. -lgainscalecalc staticlib: gainscalecalc_static.o $(AR) $(ARFLAGS) libgainscalecalc.a gainscalecalc_static.o $(RANLIB) libgainscalecalc.a chmod 777 libgainscalecalc.a dynamiclib: gainscalecalc_dynamic.o $(CC) -shared -o libgainscalecalc.so gainscalecalc_dynamic.o chmod 777 libgainscalecalc.so Edit: Linking against the shared libraries compiles fine, I just haven't tested them out yet

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  • C & MinGW: Hello World gives me the error "programm too big to fit in memory"

    - by user1692088
    I'm new here. Here's my problem: I installed MinGW on my Windows 7 Home Premium 32-bit Netbook with Intel Atom CPU N550, 1.50GHz and 2GB RAM. Now I made a file named hello.h and tried to compile it via CMD with the following command: "gcc c:\workspace\c\helloworld\hello.h -o out.exe" It compiles with no error, but when I try to run out.exe, it gives me following error: "program too big to fit in memory" Things I have checked: I have added "C:\MinGW\bin" to the Windows PATH Variable I have googled for about one hour, but ever since I'm a newbie, I can't really figure out what the problem is. I have compiled the same code on my 64-bit machine, compiles perfectly, but cannot be run due to 64-bit <- 16-bit problematic. I'd really appreciate, if someone could figure out, what the problem is. Btw, here's my hello.h: #include <stdio.h> int main(void){ printf("Hello, World\n"); } ... That's it. Thanks for your replies. Cheers, Boris

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  • non-copyable objects and value initialization: g++ vs msvc

    - by R Samuel Klatchko
    I'm seeing some different behavior between g++ and msvc around value initializing non-copyable objects. Consider a class that is non-copyable: class noncopyable_base { public: noncopyable_base() {} private: noncopyable_base(const noncopyable_base &); noncopyable_base &operator=(const noncopyable_base &); }; class noncopyable : private noncopyable_base { public: noncopyable() : x_(0) {} noncopyable(int x) : x_(x) {} private: int x_; }; and a template that uses value initialization so that the value will get a known value even when the type is POD: template <class T> void doit() { T t = T(); ... } and trying to use those together: doit<noncopyable>(); This works fine on msvc as of VC++ 9.0 but fails on every version of g++ I tested this with (including version 4.5.0) because the copy constructor is private. Two questions: Which behavior is standards compliant? Any suggestion of how to work around this in gcc (and to be clear, changing that to T t; is not an acceptable solution as this breaks POD types). P.S. I see the same problem with boost::noncopyable.

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  • Compile time float packing/punning

    - by detly
    I'm writing C for the PIC32MX, compiled with Microchip's PIC32 C compiler (based on GCC 3.4). My problem is this: I have some reprogrammable numeric data that is stored either on EEPROM or in the program flash of the chip. This means that when I want to store a float, I have to do some type punning: typedef union { int intval; float floatval; } IntFloat; unsigned int float_as_int(float fval) { IntFloat intf; intf.floatval = fval; return intf.intval; } // Stores an int of data in whatever storage we're using void StoreInt(unsigned int data, unsigned int address); void StoreFPVal(float data, unsigned int address) { StoreInt(float_as_int(data), address); } I also include default values as an array of compile time constants. For (unsigned) integer values this is trivial, I just use the integer literal. For floats, though, I have to use this Python snippet to convert them to their word representation to include them in the array: import struct hex(struct.unpack("I", struct.pack("f", float_value))[0]) ...and so my array of defaults has these indecipherable values like: const unsigned int DEFAULTS[] = { 0x00000001, // Some default integer value, 1 0x3C83126F, // Some default float value, 0.005 } (These actually take the form of X macro constructs, but that doesn't make a difference here.) Commenting is nice, but is there a better way? It's be great to be able to do something like: const unsigned int DEFAULTS[] = { 0x00000001, // Some default integer value, 1 COMPILE_TIME_CONVERT(0.005), // Some default float value, 0.005 } ...but I'm completely at a loss, and I don't even know if such a thing is possible. Notes Obviously "no, it isn't possible" is an acceptable answer if true. I'm not overly concerned about portability, so implementation defined behaviour is fine, undefined behaviour is not (I have the IDB appendix sitting in front of me). As fas as I'm aware, this needs to be a compile time conversion, since DEFAULTS is in the global scope. Please correct me if I'm wrong about this.

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  • Valgrind 'noise', what does it mean?

    - by Chris Huang-Leaver
    When I used valgrind to help debug an app I was working on I notice a huge about of noise which seems to be complaining about standard libraries. As a test I did this; echo 'int main() {return 0;}' | gcc -x c -o test - Then I did this; valgrind ./test ==1096== Use of uninitialised value of size 8 ==1096== at 0x400A202: _dl_new_object (in /lib64/ld-2.10.1.so) ==1096== by 0x400607F: _dl_map_object_from_fd (in /lib64/ld-2.10.1.so) ==1096== by 0x4007A2C: _dl_map_object (in /lib64/ld-2.10.1.so) ==1096== by 0x400199A: map_doit (in /lib64/ld-2.10.1.so) ==1096== by 0x400D495: _dl_catch_error (in /lib64/ld-2.10.1.so) ==1096== by 0x400189E: do_preload (in /lib64/ld-2.10.1.so) ==1096== by 0x4003CCD: dl_main (in /lib64/ld-2.10.1.so) ==1096== by 0x401404B: _dl_sysdep_start (in /lib64/ld-2.10.1.so) ==1096== by 0x4001471: _dl_start (in /lib64/ld-2.10.1.so) ==1096== by 0x4000BA7: (within /lib64/ld-2.10.1.so) * large block of similar snipped * ==1096== Use of uninitialised value of size 8 ==1096== at 0x4F35FDD: (within /lib64/libc-2.10.1.so) ==1096== by 0x4F35B11: (within /lib64/libc-2.10.1.so) ==1096== by 0x4A1E61C: _vgnU_freeres (vg_preloaded.c:60) ==1096== by 0x4E5F2E4: __run_exit_handlers (in /lib64/libc-2.10.1.so) ==1096== by 0x4E5F354: exit (in /lib64/libc-2.10.1.so) ==1096== by 0x4E48A2C: (below main) (in /lib64/libc-2.10.1.so) ==1096== ==1096== ERROR SUMMARY: 3819 errors from 298 contexts (suppressed: 876 from 4) ==1096== malloc/free: in use at exit: 0 bytes in 0 blocks. ==1096== malloc/free: 0 allocs, 0 frees, 0 bytes allocated. ==1096== For counts of detected errors, rerun with: -v ==1096== Use --track-origins=yes to see where uninitialised values come from ==1096== All heap blocks were freed -- no leaks are possible. You can see the full result here: http://pastebin.com/gcTN8xGp I have two questions; firstly is there a way to suppress all the noise? --show-below-main is set to no by default, but there doesn't appear to be a --show-after-main equivalent.

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  • C89, Mixing Variable Declarations and Code

    - by rutski
    I'm very curious to know why exactly C89 compilers will dump on you when you try to mix variable declarations and code, like this for example: rutski@imac:~$ cat test.c #include <stdio.h> int main(void) { printf("Hello World!\n"); int x = 7; printf("%d!\n", x); return 0; } rutski@imac:~$ gcc -std=c89 -pedantic test.c test.c: In function ‘main’: test.c:7: warning: ISO C90 forbids mixed declarations and code rutski@imac:~$ Yes, you can avoid this sort of thing by staying away from -pedantic. But then your code is no longer standards compliant. And as anybody capable of answering this post probably already knows, this is not just a theoretical concern. Platforms like Microsoft's C compiler enforce this quick in the standard under any and all circumstances. Given how ancient C is, I would imagine that this feature is due to some historical issue dating back to the extraordinary hardware limitations of the 70's, but I don't know the details. Or am I totally wrong there?

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  • adding virtual function to the end of the class declaration avoids binary incompatibility?

    - by bob
    Could someone explain to me why adding a virtual function to the end of a class declaration avoids binary incompatibility? If I have: class A { public: virtual ~A(); virtual void someFuncA() = 0; virtual void someFuncB() = 0; virtual void other1() = 0; private: int someVal; }; And later modify this function to: class A { public: virtual ~A(); virtual void someFuncA(); virtual void someFuncB(); virtual void someFuncC(); virtual void other1() = 0; private: int someVal; }; I get a coredump from another .so compiled against the previous declaration. But if I put someFuncC() at the end of the class declaration (after "int someVal"), I don't see coredump anymore. Could someone tell me why this is? And does this trick always work? PS. compiler is gcc, does this work with other compilers?

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  • Linker error: wants C++ virtual base class destructor

    - by jdmuys
    Hi, I have a link error where the linker complains that my concrete class's destructor is calling its abstract superclass destructor, the code of which is missing. This is using GCC 4.2 on Mac OS X from XCode. I saw http://stackoverflow.com/questions/307352/g-undefined-reference-to-typeinfo but it's not quite the same thing. Here is the linker error message: Undefined symbols: "ConnectionPool::~ConnectionPool()", referenced from: AlwaysConnectedConnectionZPool::~AlwaysConnectedConnectionZPool()in RKConnector.o ld: symbol(s) not found collect2: ld returned 1 exit status Here is the abstract base class declaration: class ConnectionPool { public: static ConnectionPool* newPool(std::string h, short p, std::string u, std::string pw, std::string b); virtual ~ConnectionPool() =0; virtual int keepAlive() =0; virtual int disconnect() =0; virtual sql::Connection * getConnection(char *compression_scheme = NULL) =0; virtual void releaseConnection(sql::Connection * theConnection) =0; }; Here is the concrete class declaration: class AlwaysConnectedConnectionZPool: public ConnectionPool { protected: <snip data members> public: AlwaysConnectedConnectionZPool(std::string h, short p, std::string u, std::string pw, std::string b); virtual ~AlwaysConnectedConnectionZPool(); virtual int keepAlive(); // will make sure the connection doesn't time out. Call regularly virtual int disconnect(); // disconnects/destroys all connections. virtual sql::Connection * getConnection(char *compression_scheme = NULL); virtual void releaseConnection(sql::Connection * theConnection); }; Needless to say, all those members are implemented. Here is the destructor: AlwaysConnectedConnectionZPool::~AlwaysConnectedConnectionZPool() { printf("AlwaysConnectedConnectionZPool destructor call"); // nothing to destruct in fact } and also maybe the factory routine: ConnectionPool* ConnectionPool::newPool(std::string h, short p, std::string u, std::string pw, std::string b) { return new AlwaysConnectedConnectionZPool(h, p, u, pw, b); } I can fix this by artificially making my abstract base class concrete. But I'd rather do something better. Any idea? Thanks

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  • "variable tracking" is eating my compile time!

    - by wowus
    I have an auto-generated file which looks something like this... static void do_SomeFunc1(void* parameter) { // Do stuff. } // Continues on for another 4000 functions... void dispatch(int id, void* parameter) { switch(id) { case ::SomeClass1::id: return do_SomeFunc1(parameter); case ::SomeClass2::id: return do_SomeFunc2(parameter); // This continues for the next 4000 cases... } } When I build it like this, the build time is enormous. If I inline all the functions automagically into their respective cases using my script, the build time is cut in half. GCC 4.5.0 says ~50% of the build time is being taken up by "variable tracking" when I use -ftime-report. What does this mean and how can I speed compilation while still maintaining the superior cache locality of pulling out the functions from the switch? EDIT: Interestingly enough, the build time has exploded only on debug builds, as per the following profiling information of the whole project (which isn't just the file in question, but still a good metric; the file in question takes the most time to build): Debug: 8 minutes 50 seconds Release: 4 minutes, 25 seconds

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  • GNU C++ how to check when -std=c++0x is in effect?

    - by TerryP
    My system compiler (gcc42) works fine with the TR1 features that I want, but trying to support newer compiler versions other than the systems, trying to accessing TR1 headers an #error demanding the -std=c++0x option because of how it interfaces with library or some hub bub like that. /usr/local/lib/gcc45/include/c++/bits/c++0x_warning.h:31:2: error: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options. Having to supply an extra switch is no problem, to support GCC 4.4 and 4.5 under this system (FreeBSD), but obviously it changes the picture! Using my system compiler (g++ 4.2 default dialect): #include <tr1/foo> using std::tr1::foo; Using newer (4.5) versions of the compiler with -std=c++0x: #include <foo> using std::foo; Is there anyway using the pre processor, that I can tell if g++ is running with C++0x features enabled? Something like this is what I'm looking for: #ifdef __CXX0X_MODE__ #endif but I have not found anything in the manual or off the web. At this rate, I'm starting to think that life would just be easier, to use Boost as a dependency, and not worry about a new language standard arriving before TR4... hehe.

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  • Freestanding ARM C++ Code - empty .ctors section

    - by Matthew Iselin
    I'm writing C++ code to run in a freestanding environment (basically an ARM board). It's been going well except I've run into a stumbling block - global static constructors. To my understanding the .ctors section contains a list of addresses to each static constructor, and my code simply needs to iterate this list and make calls to each function as it goes. However, I've found that this section in my binary is in fact completely empty! Google pointed towards using ".init_array" instead of ".ctors" (an EABI thing), but that has not changed anything. Any ideas as to why my static constructors don't exist? Relevant linker script and objdump output follows: .ctors : { . = ALIGN(4096); start_ctors = .; *(.init_array); *(.ctors); end_ctors = .; } .dtors : { . = ALIGN(4096); start_dtors = .; *(.fini_array); *(.dtors); end_dtors = .; } -- 2 .ctors 00001000 8014c000 8014c000 00054000 2**2 CONTENTS, ALLOC, LOAD, DATA <snip> 8014d000 g O .ctors 00000004 start_ctors <snip> 8014d000 g O .ctors 00000004 end_ctors I'm using an arm-elf targeted GCC compiler (4.4.1).

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