Ph. Gautron, M. Shapiro, Two extensions to C++: A dynamic link editor and inner data, Proceedings and additional papers, Usenix C++ Workshop, Berkeley, november 1987  Home/Search   Document Not in Database   Summary   Related Articles   Check

....of its class. Since a variable may refer to an object of several different classes (provided they are in a class subclass relationship) this scheme allows a dynamic binding of a method to the corresponding code. This scheme has also been enhanced to provide dynamic linking and loading of code [Gautron 87] While our addressing scheme is based on the same principle, there are three important constraints not present in the original C scheme: persistence, sharing, and distribution. Therefore, we must uniformly resolve references from different segments to a shared segment, which may ....

Ph. Gautron, M. Shapiro, Two extensions to C++: A dynamic link editor and inner data, Proceedings and additional papers, Usenix C++ Workshop, Berkeley, november 1987

....of data objects. 3 Code sharing is not addressed in this test. For example, in E, code must be always mapped from the beginning of the application, while data objects are mapped unmapped on demand. Other class based systems allow mapping of class objects, like CLAMP [Call 87] or SOS [Gautron 87] CLAMP is an object oriented graphical system, were classes are explicitly loaded by the programmer before used. In SOS, classes are loaded when an instance is created. A new keyword in the language forces the preprocessor to insert an explicit test in the object constructor, mapping the class ....

Philippe Gautron and Marc Shapiro. Two extensions to c++: A dynamic link editor and inner data. In USENIX C++ Workshop, Santa Fe, New Mexico, November 1987.

....the class hierarchy of a C program at the expense of additions to the programming language and or restrictions on the class hierarchy of programs. The CLAM [3] and Andrew [23] projects also supported a restricted form of class hierarchy expansion. ffl SOS, P. Gautron and M. Shapiro, 1987, 1989 [10] [27] The design and implementation of a dynamic loader and linker for the C language is discussed in [10, 27] In support of the dynamic loading of class methods, new keywords are introduced into the C language. The declaration of a dynamic class causes all method invocations for that class ....

....on the class hierarchy of programs. The CLAM [3] and Andrew [23] projects also supported a restricted form of class hierarchy expansion. ffl SOS, P. Gautron and M. Shapiro, 1987, 1989 [10] 27] The design and implementation of a dynamic loader and linker for the C language is discussed in [10, 27]. In support of the dynamic loading of class methods, new keywords are introduced into the C language. The declaration of a dynamic class causes all method invocations for that class to use 67 indirection through a table of function pointers. Constructor functions, that are statically linked, ....

Gautron, P., and Shapiro, M. Two extensions to C++: A dynamic link editor and inner data. In USENIX Proceedings and Additional Papers C++ Workshop (1987), USENIX Association, pp. 23--34. 86

.... Dynamic linking is an integral part of single user open operating systems such as Cedar [57] and has been implemented under Unix as part of such self contained environments as Emerald [27] and the Portable Common Runtime [61] The CLAM user interface system [10] and SOS distributed object system [21] load C classes dynamically; the latter is based on the Andrew project s Camphor dynamic linker. Our work differs from these projects in its use of dynamic linking to share potentially writable objects transparently, between ordinary Unix programs. 4. Implementation Details 4.1. Static Linker ....

P. Gautron and M. Shapiro, "Two Extensions to C++: A Dynamic Link Editor and Inner Data," Proceedings of the USENIX C++ Workshop, November 1987, pp. 23-32.

....that dossier objects are loaded for subsequent fully polymorphic manipulation. One may also consider the more exotic possibility of changing the definition of a class on the fly (class evolution) e.g. by rebinding functions or adding members, or even altering the types of existing members [GS87]. In light of the restrictions sketched in x4.1, it is only reasonable to consider rebinding of C virtual functions, since C systems generally allocate virtual function tables in data segments, and hence remain unfrozen. This also applies to method function interposition. Finally, we turn to ....

Philippe Gautron and Marc Shapiro. Two extensions to C++: A dynamic link editor and inner data. In USENIX Proceedings and Additional Papers C++ Workshop, pages 23--34. USENIX Association, 1987.

....the data, if needed. 3.5 Dynamic linking The SOR group had previously extended the C language with a new keyword dynamic, to mark classes and instances which can migrate, and to simplify dynamic linking. We now consider it was a mistake to change C itself. The dynamic extension, described in [Gautron 1987], is now handled by FOG instead. 3.6 Type checking The FOG compiler checks for compatibility between declarations of each end of a channel: for each client procedure, its counterpart with the same name and signature, is searched among all server stubs in the same FO. Our remote type checking is ....

Philippe Gautron and Marc Shapiro. Two extensions to C++: A dynamic link editor and inner data. In Proceeding and additional papers, C++ Workshop, Berkeley, CA (USA), November 1987. USENIX.

....2 Conceptually a type reference is the reference of a type object, e.g. one that contains a description of the type, but there is no obligation to keep such an object around at run time. The implementation of a type reference could just be a hash of its interface (as in Lynx [17] SOS C [8], and Network Objects [ or some other compact representation. 2.3 Handle primitives The primitive operations on handles are listed below. This list is very general; we contend that all reference systems can be specified as a suitable combination of these primitives. Note the absence of an ....

Philippe Gautron and Marc Shapiro. Two extensions to C++: A dynamic link editor and inner data. In Proceeding and additional papers, C++ Workshop, Berkeley, CA (USA), November 1987. USENIX.

....that the program can be type checked statically. This is not necessarily true when we consider persistent or remote objects: we have to be able to type check them to detect user errors. These compilers need to be extended to emit type information, that can later be used for run time type checking [5]. The binding procedure can be responsible for limited type checking. Since objects are not supposed to change type dynamically, verification at binding time seems to be a reasonable option. The type information can be stored in the maillon itself or in a place where it can be recovered using the ....

Philippe Gautron and Marc Shapiro. Two extensions to C++: A dynamic link editor and inner data. In Proceeding and additional papers, C++ Workshop, Berkeley, CA (USA), November 1987. USENIX.

....generic. To support objects from a different language than C , possibly with a different object model, it should suffice (hopefully) to attach appropriate prerequisites and upcall methods to those objects. 1 OSOS not OS=2 but indeed OS 2 2 We have implemented a dynamic linker for C [6]. 3 We have implemented a context independent pointer class permPtr [13] SOS is built using its own mechanisms: all the SOS system services are implemented as fragmented objects with local proxy interfaces. These include an object manager (called the Acquaintance Service) a flexible Name ....

Philippe Gautron and Marc Shapiro. Two extensions to C++: A dynamic link editor and inner data. In Proceeding and additional papers, C++ Workshop, Berkeley, CA (USA), November 1987. USENIX.

....even though SOS as an OS has no concept of type, it maintains prerequisites , allowing the C run time to implement dynamic type checking and linking. The structure and management of elementary objects are decribed in [16, 4] The mechanics of the dynamic type checker and linker are described in [2]. SOS has been implemented in C , on top of Unix. It supports object migration, persistent object, dynamic linking, and arbitrarily complex user defined objects (written in C or FOG) Existing system services (all structured as fragmented objects) are: a distributed object manager [4] a ....

Philippe Gautron and Marc Shapiro. Two extensions to C++: A dynamic link editor and inner data. In Proceedings and additional papers, C++ Workshop, Berkeley, CA (USA), November 1987. USENIX.

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