//ERROR:OverloadisAmbiguous:Point::Point(float,float) }.

In addition, other compilers, like Clang, do not suffer the issue. Fred&x() classFred{ In the very rare cases when statics need to be static and they depend on each other, wap them in static methods. your chances of survival by preventing disasters in a systematic way, you arrays are evil), you don't have to have a default //Filex.cpp If you get unlucky, then the this pointer will be garbage, which will appear to indicate it has been initialized. The assertion can be customized by further defining an ATUM_LIFETIME_ASSERT(Cond) macro, which defaults to assert(Cond).

This is a crummy option, but we don't know how else to improve the situation. Note: The static initialization order fiasco does not apply to

Asking for help, clarification, or responding to other answers. We can only say minimize because some are required (also see Don't Use C++ Statics below).

Is there a faction in the Ukrainian parliament favoring an immediate ceasefire?

In contrast the following constructor uses assignment: Fred::Fred(){x_=whatever;}. Other things that don't work when attempting to remediate the issue are discussed below. Difference between static class and singleton pattern? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. On the other hand, Plain Old Datayptes (PODs) require the use of static because a C++ object can displace when the initialization of the POD occurs. staticFred*ans=newFred(); If you didn't do A "default constructor" is a constructor that can be called with The problem does not affect plain old datatypes (POD) (like integers and pointers). Constructors." But, really, it is best to avoid using statics if at all possible. Here, reliably and efficiently implies a few things, like guaranteeing the compiler pools all uses on the string AAD, which is what the AAD_CHANNEL provides. However, we view it as a crummy option because a user lost a choice. Note: You don't have to do this for builtin/intrinsic types like int or For example if you create a static or global float object, there

We're hiring more fabulous people so write me if that's

If you must use statics (i.e. Does return-by-value mean extra copies and extra overhead? }; Fred::Fred() The only time the static initialization order is truly a fiasco Point object). overloaded constructors: classPoint{ compile time. If you're using a nifty initialized global A in the constructor of some variable template or static data member of a template, it is not guaranteed to work. Since BufferTrandsformation and DEFAULT_CHANNEL are cornerstones of most Crypto++ classes, the dependency issue almost always exists.

chambers, you can stop reading here.

The Tag argument is some type that just has to be different for each atum::lazy_init object. Fred(inti,intj);

constructor body's "{") might, for example, allocate some default

}; However it is possible (and even likely) that a default constructor can take Use the Init class atum::lazy_init to declare a global variable that is initialized on first use or when .initialize() is called (whatever happens first).

You signed in with another tab or window. The software had AAA logging requirements, and the program crashed upon exit when logging the shutdown because the channel string was destroyed too soon. This would create an ambiguity error in the How to reliably detect a MacPorts-ported compiler? Should my constructors use "initialization lists" or "assignment"?

If the C++ committee ever addresses the issue (with something other than Ostrich Algorithm), then the library will use it. The C++ FAQ Book has a second technique that answers this @jww Code with that problem has serious inter-dependency problems and should be refactored. That's because the compiler driver effectively invokes the linker with myprogram.o libcryptopp.a rather than libcryptopp.a myprogram.o. X's methods: voidX::someMethod() { case, the object's default constructor (implicitly called before the

}; The linker will holler at you ("Fred::j_isnotdefined") unless you Minimally they initialize internally used fields. Thanks for contributing an answer to Stack Overflow! These static methods are the so-called "Named staticPointrectangular(floatx,floaty);//Rectangularcoord's Unfortunately, the GCC folks don't recommend it, and the toolchain recently broke some projects that were using the feature. In case the static variables do depend on each other, just wrap them in static functions: Most (90%? Then function f() declares The lazy initialization is done in a thread-safe way by leveraging a function local static. j_(42)//Error:youcannotinitializestaticmemberdatalikethis This is a complete remediation to the compile failure, and it only needs to be done once. only initialized once (the first time control flows over their declaration), so

With the Named Constructor Idiom, you declare all the class's constructors in

From a performance perspective, it is important to note that the x.goBowling(); For example, if we have two objects x and y, and construction of y will fail if x has not been constructed, then construct x first and supply it to the constructor (or another member) of y). Use the Init class atum::nifty_init to declare a global variable that is initialized using nifty counters. We can only say can because the problem surfaces under certain conditions, and its not readily apparent to the user that the problem has surfaced. Second, you will witness a crash in std::string. common code in a private init() member function. This is implemented in the GNUmakefile with: This is not a complete remediation because a user's C++ static objects are not included in the static archive. The library will then keep track whether a global has been initialized and error on access of an uninitialized object. main() The problem is the order of initialization is only guaranteed within a translation unit, and the C++ language provides no facilities to control initialization order when multiple translation units or object files are combined into a library or program. If there are no dependencies to other statics, make the static data const/constexpr. | Find centralized, trusted content and collaborate around the technologies you use most.

and read the topic about how to prevent the static initialization order "fiasco". classPoint{

On the other hand if you like to improve If you are using Crypto++ 5.6.2 or less, then you should upgrade to Crypto++ 5.6.3. You have answered your own question. One possibility is the trick with the static function member: Indeed, this does work. See gcc46, gcc47 'init_priority' attribute is not supported on this platform for more details. Apple supplied GCC does not suffer the issue. Set #define CRYPTOPP_INIT_PRIORTY=0 in Crypto++'s config.h - setting #define CRYPTOPP_INIT_PRIORTY to 0 disables the feature. Also see How to reliably detect a MacPorts-ported compiler?

for users of your class. Can one constructor of a class call another constructor of the same class to initialize the, Which constructor gets called when I create an array of.

In the rare cases when statics are required for a reason or another and they do not depend on other statics, declare static variables. [10.3] How can I make a constructor call another constructor as a public: They turn a pile of arbitrary bits static data member into a static member function: //FileX.hpp Because you must explicitly define your class's static data Points in either coordinate system: main()

available that handle these changes; watch this space for an update in the staticFred&x=X::x();

Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Making statements based on opinion; back them up with references or personal experience.

staticPointpolar(floatradius,floatangle);//Polarcoordinates on the MacPorts Users mailing list. Every subsequent call will return an array of Fred (which you probably should be doing anyway since It does not build its ports using its compilers. x().goBowling(); By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. classX{ You can now choose to sort by Trending, which boosts votes that have happened recently, helping to surface more up-to-date answers. Does anyone know how to ensure that static objects are created in the correct order? // future.). that: the global Fred object is constructed on its first use. }; //FileX.cpp Static initialization order is undefined, and the most elegant way around it (while still doing static initialization i.e.

[C++ FAQ Lite Update: Thank you for your reactions. temporary local object; it does not initialize this object. Note: we take no position on how MacPorts fixed it. amount of memory or open some default file. public: Constructors are like "init functions". 99%?) The C++ Static Initialization Order Fiasco is a well known problem with C++ programs that use static class objects. A POD must have a static qualifier if a C++ object is directly or indirectly interacting with it. Also see Apple's Module Initializers and Finalizers. Just use the same technique just Use the "construct on first use" idiom, which simply means to wrap your are the same: two floats. whatever will be constructed directly inside x_. It can be used to initialize atum::manual_init variables, but is also valid for all other Init classes. y's constructor will call a method on the x object, yet the x object only the first call to .initialize() and last call to .destroy() will actually initialize/destroy the object; the others have no effect. Why doesn't the construct-on-first-use idiom use a static object instead of a static pointer? Regrettably, it indeed seems like I have answered my own question. not refactoring it away completely) is to wrap the initialization in a function.

constructed before x, which happens 50% of the time since they're in //

Otherwise, users of B will not get the static nifty counter object that will initialize A. :x_(x),y_(y){}

// @jww: The only reasonable alternative is to do what the OP themselves suggest in the question. [10.6] Should my constructors use "initialization lists" or "assignment"? However, when you want to initialize a static instance with an instance in another compilation unit, the order seems impossible to specify.

usingnamespacestd;

order. // //

Valgrind flags them as uninitialized even though they are file scope PODs with 0-value that are supposed to be initialized by the BSS. and this temporary object is passed into the x_ object's assignment }. As a rule of thumb, if you have a lot of the second and third cases, you are not doing enough of the first. public: Note: this problem appears to be local to MacPorts and its GCC. is when your static or global objects have a constructor.

// All that really happens in this case is a slight of hand - one problem was transformed into another problem. This can create resource leaks. initialization order is truly a fiasco is when your static or global Fred*p=newFred[10];//ERROR:Freddoesn'thaveadefaultconstructor

For example if you create a Fred(); It is very similar to atum::manual_init but uses a counter to allow calling .initialize() and .destroy() multiple times: :i_(10)//OK:youcan(andshould)initializememberdatathisway default constructor: classFred{ The recommended way is to perform initialization in the beginning of main() and destruction at the end. |Tableofcontents The classical C++ static initialization order fiasco revisited, Static initialization order fiasco for built-in objects/libraries. Until the C++ committee provides the support, it will be a intermittent, hit or miss problem. Turns out there are two common ways to specify a 2-space To subscribe to this RSS feed, copy and paste this URL into your RSS reader.

Additionally, MacPorts provides no way to detect the compiler it supplies when the library and programs are being compiled, so the project is in a uncomfortable position. In practice, you can have situations where static data is needed. define (as opposed to merely declare) Fred::j_ in (exactly) one of your The Crypto++ library has three static C++ objects that are sensitive to initialization order. someMethod() method during static initialization, then you're at the The third remediation attempts to ensure the object files are linked in an order that respects implicit dependency needs. Lifetime checking is enabled by defining ATUM_CHECK_LIFETIME to 1 (defaults to no checking). Fred.cpp (or Fred.C or whatever source file extension you use).

How to change MacPorts config setting before building a Package? You have to manually ensure that the globals are initialized before their first use and in the correct order to handle inter-global dependencies. Fredx; //Filey.cpp The random number generator uses the string DEFAULT_CHANNEL, so the string must be constructed first. Pointp1=Point::rectangular(5.7,1.2);//Obviouslyrectangular Initialization is done using an Initializer, which controls how the object is initialized: The helper class atum::scoped_initializer takes some Init objects as template parameter and will call .initialize() on all of them in its constructor and .destroy() in its destructor (in reverse order). The TLDR portion of this page: if you compile the library and the library is Crypto++ 5.6.3 or higher, then you should perform the following. Suppose you have a class X that has a static Fred object: //FileX.hpp Freda[10];//ERROR:Freddoesn'thaveadefaultconstructor

seg fault when using global object static member, C++ global string shows up in different values, global scoped variables in c++ not properly initialized, std::map initialization does not work when using const variables as keys, The meaning of "static char __ = []() -> char", std::map exception [ read access violation _Wherenode was nullptr.

builtin/intrinsic types like int or char*.

I hear they're hiring down at McDonalds. // As a concrete example, g++ myprogram.cpp -o myprogram.exe -lcryptopp performs the exact opposite of what we want and need. constructor will get run before x's constructor, and you're toast.

The second remediation attempts to gather all C++ static objects and place them in a single source file.

That's inefficient. source files: //Fred.cpp

return*ans; So my question is, is there any modern, more pattern oriented way to prevent this "fiasco" but to wrap the "static stuff" into functions??? You can Why am I getting an error after declaring a. There are some tricks discussed below in Remediations, but they are incomplete remdiations. However if you are creating an STL vector rather than Use the ATUM_CONSTINIT macro to get a compiler error if constant initialization could not be performed at compile-time (only with C++20 or on supported compilers). One way to solve this ambiguity is to use the Named Constructor Idiom: #include//Togetsin()andcos() How to help player quickly make a decision when they have no way of knowing which option is best. staticintj_;//DeclaresstaticdatamemberFred::j_ classFred{ Other ports, like Fink, do not suffer the issue. didn't allocate a large enough pool of memory or if it opened the wrong file). But if

private: Don't use a MacPorts compiler - while this seems like a poor option, it appears to be the option MacPorts itself takes by default. #include"X.hpp" main() Conclusion: All other things being equal, your code will run faster if you use Barneyy; For completeness the Barney constructor might look something like this: //FileBarney.cpp In short, suppose you have two static objects x and y which exist in example: //Fred.h

The third symptom is sometimes an uninitialized read on platforms like OS X when using Valgrind. Regrettably, you have to write globalObject().MemberFunction(), instead of globalObject.MemberFunction(), resulting in somewhat confusing and inelegant client code. C++ programs that use static class objects, MacPorts does not provide a way to detect its compiler in the preprocessor, Replace .ctors/.dtors with .init_array/.fini_array on targets supporting them, gcc46, gcc47 'init_priority' attribute is not supported on this platform.

Could a license that allows later versions impose obligations or remove protections for licensors in the future? private: x.goBowling(); this, you'll probably get an "undefinedexternal" linker error. }; Symptoms will usually surface in one of three ways. initialization lists rather than assignment. probably want to read the next FAQ. The classes ending with _init all have an interface that looks like this: They hold an object of the specified type and provide pointer-like access as well as a .get() method. This page was last edited on 14 April 2021, at 08:58. Fred();//Defaultconstructor:canbecalledwithnoargs }. Use a MacPorts supplied Crypto++ - MacPorts has worked around the issue, so you should not experience trouble when choosing this option. For [10.7] What is the "Named Constructor Idiom"? A technique that provides more intuitive and/or safer construction operations explicitly defined in exactly one compilation unit.

I have searched a long time for a solution, trying all of them (including the Schwarz Counter solution), but I begin to doubt there is one that really works. And there's no way for the compiler to pool the use of a nil NameValuePair because pooling occurs on C-strings. objects have a constructor. public: members. MACPORTS_GCC_COMPILER is set on the command line by the GNUmakefile. rev2022.7.21.42635.

different source files. Is there an apt --force-overwrite option? }. |Subjectindex The modern, more pattern-oriented way is not to use globals in the first place. When the dynamic library is created from the static archive, the constructors for the C++ objects cryptlib.o are invoked first. vectora(10,Fred(5,7)); }. misunderstood aspect of C++. }; SystemVerilog Array of Bits to Int Casting, Static class variables and methods in Python. the x object: //Filex.cpp return*ans; In other words, do not have static state at all. List: voidg() Fred(inti=3,intj=5);//Defaultconstructor:canbecalledwithnoargs Constructors should initialize all member objects in the initialization list. if the whatever expression and/or assignment operator causes the object We can only say attempts because the problem is a defect in the C++ language, and the work arounds are not a complete remediation. Normally, global initialization between translation units is done in an unspecified order, which makes it problematic to access global variables in the constructors of other global variables. Under GCC compatible compilers, init_priority is used. //

For example, static bool flag = false is different than bool flag = false because the initialization order fiasco affects the initialization of the of flag. initialization list: Fred::Fred():x_(whatever){}. The first remediation attempts to avoid or minimize the problem by avoiding the use of static C++ variables. No. Its set by the makefile because MacPorts does not provide a way to detect its compiler in the preprocessor. Since static local objects are constructed the first time control flows over combine both constructors by using a default parameter, or you can share their For example, Solaris and MacPorts GCC compilers fail to compile a program with init_priority (also see MacPorts Issue 37664). char*.

classFred{ public:

Additionally, its not clear to us how to use linker scripts of other platforms, like Solaris. In addition, the test driver program, cryptest.exe, has one static C++ object (a global random number generator), and it is located in test.cpp. Dragons be here: if you call another constructor, the compiler initializes a Difference between /usr/bin/strings and gstrings from binutils? But this seems to me a rude workaround. hasn't yet been constructed. There's another source of inefficiency as well: in the second (assignment) Use the Init class atum::manual_init to declare a global variable that has to be initialized manually. arguments, provided they are given default values: classFred{

global function. #include"Barney.hpp" https://www.cryptopp.com/w/index.php?title=Static_Initialization_Order_Fiasco&oldid=28899, If your code has C++ static objects that depend on Crypto++ library components, then start numbering your remediations at.

c++initialization-orderstatic-order-fiascostatic-variables. { a lazily initialized global is never destroyed. Barney::Barney() For example, suppose we are building a Point class that represents a position #include"X.hpp"

differences between the constructors becomes somewhat subtle and error prone.

As they do not initialize anything in their constructors, the Init objects themselves are subject to constant initialization and thus always available. to be used to initialize the elements: #include

Static array of static members: possibility of initialization order fiasco. This page discusses the static objects, some of the symptoms and the remediations put in place to address the issue. } //

Therefore the only way to differentiate between the various constructors of a The tragedy is that you have a 50%-50% chance of dying. The declarations of objects in cryptlib.cpp under GCC compatible compilers are: The declarations of objects in cryptlib.cpp under Microsoft compatible compilers are: This is not a complete remediation because some platforms and compilers don't provide the ability to declaratively provide an explicit initialization order. the same Fred object (the one pointed to by ans). classX{ In any event, it's always portable and safe to change the X::x_ Crypto++ can suffer the static initialization fiasco on occasion. a local List object called x: voidf() This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. But if there are lots of constructors, the Crypto++ is a case in point: it has over 1400 class files, and there's no way to reliably and efficiently remove the three C++ static objects. you don't want the typing of passing arguments everywhere) make the statics to be pointers, and initialise them once (for example, in main()). But function g() declares a function called x() that returns a They A possible improvement when scaling up to larger projects is to use initialisation and accessor functions (to hide the pointer and assert that initialisation was done) and grouping initialisations by library.

And this is the exact situation that occurs when cryptest.exe (with its global random number generator) is linked against libcryptopp.a (with the static objects that need to be initialized first); and its the reason Valgrind produces the finding under Symptoms. If you need to share x and y between functions, simply pass them to functions as arguments. may also allocate resources (memory, files, semaphores, sockets, etc).

All three are located in cryptlib.cpp. //Thesestaticmethodsaretheso-called"namedconstructors" They are not a complete remediation because some platforms, configurations and use cases are left with residual gaps. set up a static Fred& instead. array of. In fact, we don't even know what they did (or of they did anything other than avoid their MacPorts compiler).

//assumethereisnodefaultconstructorinclassFred

The fourth remediation attempts to ensure C++ static objects are declared with compiler specific decorations so the compiler and linker can tend to them.

Now the users of Point have a clear and unambiguous syntax for creating Though not readily apparent, the finding is due to use of file scope bools in cpu.cpp: g_hasMMX, g_hasAESNI, g_hasCLMUL and friends. The string one is usually due to DEFAULT_CHANNEL being used before the string is constructed. static object inside a function. make sure your objects are always created via, Click here to go to the next FAQ in the "chain" of recent changes. fabulous work. Solving hyperbolic equation with parallelization in python by elucidating Mathematica algorithm. Listx();//Functionnamedx(thatreturnsaList) +1 This is a better approach than the construct on first use idiom IMHO. In fact, the author experienced this problem in high integrity software. How can I handle a constructor that fails? As you recall, static local are

Prevent static initialization order "fiasco", C++, AddressSanitizerInitializationOrderFiasco, How APIs can take the pain out of legacy system headaches (Ep. That's a false choice.

[10.13] How can I handle a constructor that fails?

Calling .initialize() will initialize it, and calling .destroy() will destroy it. If your { This is called the Construct On First Use Idiom because it does just global function, x(), that returns the Fred object by reference. Fred to have derived classes. If the C++ static objects are not initialized in an order consistent with the explicit dependencies, then your program could crash in mysterious and not-so-apparent ways. this will call X::x() only once: the first time X::someMethod() Suppose further When I use static variables in C++, I often end up wanting to initialize one variable passing another to its constructor. static/global/shared data should be dependency-injected into where it is used, and not created as static at all. Thus a constructor that takes no arguments is certainly a (both of the above assume the constructor of y requires a reference).

How are static members of templated class constructed when a static function is called?

I need to initialize private static objects, C++ Static variables in member functions, C++ The static keyword and its various uses in C++, C++ Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviations with _mm_popcnt_u64 on Intel CPUs. inlinePoint::Point(floatx,floaty) before or after the someMethod() is called. private: }. The elegant way to prevent fiasco is to never use static objects that depend on anything. staticFredx_; Two of them are std::strings (DEFAULT_CHANNEL and AAD_CHANNEL), and one of them is a Crypto++ NameValuePair class (g_nullNameValuePairs). I've experienced the crash in the dtor first hand when an object disappears too soon. Another subtle problem with this remediation is compiler drivers like Clang, GCC and ICPC work against object file ordering because they place the libraries after user object files when invoking the linker.

Unfortunately the parameters for these two coordinate systems As described above, the disaster occurs if y is

That is, if user code needs one of the Crypto++ static objects during exit, then the object may be destroyed too soon. If you are a MacPorts user attempting to use the GCC compiler, then you have the following options. "ctor" is a typical abbreviation for constructor. I guess I'll have to learn to live with it. See [17.1] for details. MacPorts supplies a GCC compiler that does not consume __attribute__ ((init_priority)) or __attribute__ ((constructor)). Then you simply change any usages of x_ to x(): voidX::someMethod() [10.1] What's the deal with constructors? Alternatively you can use the CMake target foonathan::atum either via subdirectory or installation. the compilation unit for y.cpp get initialized first, then y's The result is that, depending on the weather, it can happen that the instance that depends on another is constructed, and only afterwards the other instance is constructed. Trending is based off of the highest score sort and falls back to it if no posts are trending. However, the basic idea is the same: take control of when the initialisation and clean up is done and don't leave it to random chance. Nifty counters allow initialization that happens automatically before use, just like with atum::lazy_init, but also ensure destruction. It simply allows you to build the library without a compile failure. #include"Fred.hpp" #include"Barney.hpp" For example, if you have a global random number generator (like in test.cpp) and it is constructed before the std::string (DEFAULT_CHANNEL), then you will experience a crash in std::string because this pointer is probably NULL. If you're super performance sensitive and you're concerned about the overhead errors occur before main() begins. staticintj_; The more usual way of addressing the problem is to avoid statics whenever possible - and even more so between objects that rely on construction order. Like Atum, the Egyptian god of pre-existence and post-existence, this single-header library takes care of global variable initialization and destruction. C++ committee is working on this problem, but compilers aren't yet generally #include"Barney.hpp"