JP3293821B2 - Dynamic link system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a common section method of referring to data commonly used between a main program and a plurality of external procedures through a declaration of a common area, and more particularly, to a dynamic link between load modules having a common section. Related to dynamic linking system.

In recent years, not only general-purpose computer systems but also personal-use computer systems have been used by dynamically linking load modules, that is, executable programs themselves, for maintainability of user programs. Demands have been growing. By dynamically linking between load modules, the working area when executing a user program can be reduced, and it is possible to avoid the problem of expanding the storage disk capacity of load modules due to possession of duplicate program code. is there.

[0003]

[Prior art]

Conventionally, in a common section method in which data is shared and used between a plurality of program units, a common section is declared in a source program, compiled, linked, and input to a loader. After being load-moduleized, it could not support a mechanism for dynamically linking, and had no mechanism for identifying the presence or absence of a common section.

[0004]

[Problems to be solved by the invention]

Therefore, in the conventional loading mechanism, processing of a dynamic link between load modules holding a common section has been prohibited. For this reason, even when the user program is maintained for a plurality of load modules, the load modules cannot be replaced for each compilation unit, and static linking must be performed again. For this reason, complicated management of load modules is required, which causes problems such as wasted maintenance time and complicated management.

[0005] Furthermore, since the static link is performed, unnecessary working sets increase at the time of execution, and the storage disk capacity of the load module expands. An object of the present invention is to enable a dynamic link between a group of load modules holding a common section.

[0006]

[Means for Solving the Problems]

The present invention provides a dynamic link system for dynamically linking a plurality of load modules for which a common section has been declared, in which a second load for which a dynamic link has been requested from a first loaded module that has already been loaded. When loading the module, the comparison and determination means for comparing the length of the common section declared in the second load module with the length of the existing common section; If it is determined that the length of the common section declared in the load module is longer than the length of the existing common section, the length of the common section declared in the second load module is determined. Obtain a new area of equal length, copy the contents of the existing common section to the new area, The 該新 region as a new common section area, is characterized in that it has an access control means for accessing each of the load modules that are declared common section, the.

FIG. 1 is a principle diagram for explaining the present invention in further detail, and the present invention will be described more specifically with reference to FIG. The user program first makes a dynamic link request (CALL statement call, function call, etc.) and makes a system call. In the dynamic link mechanism, the common section presence / absence identifying means 1 determines whether the program requested to be dynamically linked is a load module with a common section (that is, whether the program is a load module for which a common section is declared). ) Is identified. The common section common control means 2 uses the conventional dynamic link mechanism if the load module requested for dynamic link does not have a common section, and if the load module has a common section, the already obtained common section exists. Whether or not to perform is checked by searching the common section common control table. If it is determined that there is no existing common section, a new common section is acquired when loading the load module required for the dynamic link. That is, a new common section common control table is created, and control is performed to set the address of the common section area to the common section pointer.

When the common section sharing control means 2 determines that there is an existing common section, the length of the common section declared in the load module required for the dynamic link is changed to the length of the existing common section. Whether the length is longer than the length is detected by the erroneous length detection means 3 of the common section. As a result, if the length of the declared common section is less than or equal to the length of the existing common section, the common section access control means 4 sets the address of the existing common section in the common section pointer area. I do. On the other hand, when the length of the declared common section is longer than the length of the existing common section, the common section access control means 4 sets the length of the common section to be equal to the length of the declared common section. After acquiring a new area, copy the contents of the existing common section into this new area and change all the common section pointers of the programs that refer to this existing common section to the addresses of the newly acquired common section area. Then, control is performed to return the previous common section area to enable access to the common section, and linking is enabled when executing a load module group in which the common section is declared.

In this way, a dynamic link between load modules for which a common section is declared is realized.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described with reference to the drawings. Generally, a machine language in which an object program runs in a direct execution form is called a load module. When creating this load module, read the program divided into several units, interpret the reference of the name that crosses the programs, and change the reference by the name to the reference by the address. Is performed. A given program has a selective loading function that selects and combines as many standard subprograms as necessary. Further, the load module is formed by substituting the initial values of the variables specified in the program.

[0011] The procedure in a program written in FORTRAN or the like is as follows.
It is divided into one main program and a plurality of subroutines, that is, external procedures. In these divided procedures, each function or subroutine is a program unit, and it is necessary to determine the locality of the effective range of a name (called a mark) in each program unit. The data referred to by its name may be confined within the program unit, may be exchanged with other program units, and may exchange data in the common section with each other through a common area or common section declaration. Sometimes referred to.

In general, when referring to data of one common section having a plurality of program units, data values in the common section are preserved during execution of those program units, but the common section is declared. After the execution of the lowest unit of the execution sequence among the program units, the value of the data in the common section becomes indefinite. For example, it is assumed that the program unit A calls the program units B and C, that is, it is calling, and the B and C share data of the common section X.

In such a case, a common section declaration is generally written in the program units B and C, and the program unit A which calls the B and C, that is, the common unit X If not, B
When the execution of C or C is completed, the value of X is undefined.

In general, a common section defined individually on a plurality of program units is therefore defined only by a source program. Since it was not possible to dynamically link between the load modules that hold the common section, problems such as the inability to switch the load modules in compilation units occurred. Thus, the present invention dynamically enables linking between load modules that hold a common section.

FIG. 2 is a configuration diagram of the present invention, and FIG. 3 is an embodiment diagram of a procedure for accessing a common section. 2 and FIG.
Is a user program, 6 is a dynamic link mechanism, 1 is an identification mechanism for identifying the presence or absence of a common section, 2 is a common section shared control mechanism, 3 is an error length detection mechanism, and 4 is an access mechanism to the common section. .

As shown in FIG. 2, in the present invention, the identification mechanism 1 identifies whether or not the load module has a common section.
If it does not have a common section, the conventional dynamic link mechanism is used. That is, since there is no common data commonly used in each program unit, a conventional dynamic link mechanism can be realized. If the identification mechanism 1 determines that the common section is included, the common section sharing control mechanism 2 searches the common section sharing control table to determine whether or not the common section has already been loaded into the main storage device. Find out by. If the common section has not been loaded, the common section is newly loaded into the main storage device, and a common section shared control table is newly created. Then, the address of the common section area, that is, FIG.
Is set to the common section pointer A shown in FIG. in this case,
The common section pointer A is always created in a writable section, and a reference to a common section from a write-protected section is always made via a writable section.

If the common section area 7 has already been loaded into the main storage device, it is determined whether the length of the loaded common section area is equal to or greater than the required common section length, that is, the length of the defined area. Is checked by the erroneous length detection mechanism 3 of the common section. The erroneous length in the common section erroneous length detection mechanism 3 refers to a state where the common section definition length is different. If the request length of the loaded common section is long, the start address 8 of the loaded common section area 7 is set to the common section pointer area, that is, the common section pointer A shown in FIG. On the other hand, if the length of the loaded common section area 7 is short, a new common section area 7 is obtained, and the contents of the loaded common section area 7 are copied there. Is changed to the start address 8 of the newly acquired common section area 7 of the program that refers to, and the area of the previously loaded common section is returned. Note that the length of the common section area defined separately in multiple source programs does not need to be the same, and the maximum length of these common section definitions is adopted during dynamic linking. Become.

An access procedure to the common section is performed as shown in FIG. To access the common section, first, a writable area on the main memory, that is, a writable section is used to first access the common section address, that is, the common section area 7 shown in the lower part of FIG. FIG. 3 shows the start address 8
And the data in the common section area 7 is accessed based on the start address 8 as shown in FIG. Here, the base is an address that forms the basis of a relative address. Between program units, data in the common section is accessed by a method such as a relative address from the beginning of the program unit.

FIG. 4 is an example of a program corresponding to a load module that holds a common section according to the common section dynamic link method of the present invention. The program is written in assembler language for clarity, but it is assumed that this is actually a load module. Program unit A calls program B with a CALL statement (CALL B). That is, the program A is higher than the program B, and both the program units A and B declare the data of the common section called the mark X in common. In this case, since the common section X is declared in both the upper program unit A and the lower program unit B, the value of X at the end of the execution of the program unit B is not determined. Instead, data values can be exchanged between A and B through X. If the common section X is not declared in the program A, the value of X at the time when the execution of the program B ends is undefined.

As described above, the execution of a call between program units generally has a main structure, and when one or a plurality of common sections are referred to in a plurality of program units, a declaration is made during the execution of these program units. The values of the data in the common section are preserved between programs that have common sections.

The operation sequence of the embodiment shown in FIG. 4 is as follows. 1) Execute program A (EXEC PGM = A). 2) The dynamic link mechanism acquires the common section area having the mark X when loading the program A, and stores the address in the address constant XCOM in the program X. 3) The dynamic link mechanism passes control to program A. 4) After the program A executes and changes or refers to the contents of the common section area, the program B is dynamically linked.
Call. 5) When loading the program B, the dynamic link mechanism first searches the virtual address space with the mark X. In the example, the name X can be found and the common section length is compared. However, since the length is different, the longer length is newly acquired and the contents are copied from the old area to the new area. The address of the new area is stored in the address constant area of program A and program B (XCOM and YCOM). 6) The dynamic link mechanism passes control to program B. 7) The program B is executed to change or refer to the contents of the common section area.

First, when the program A is executed, the dynamic link mechanism of the present invention acquires a common section area having the mark X when the program A is loaded. As shown in the figure, if the data length of this common section is 100 A and its address is A (X), the address is stored in the address constant XCOM in the program X. Thereafter, control of the dynamic link mechanism is passed to the program A.
When the program A is executed, the contents of X are changed and referenced during the execution, so that the contents of the common section area are changed accordingly. The value thus changed is transferred to program B in order to call program B at (CALL B). At this time, program B
X is common data of the common section.

Therefore, the value updated by the program A is
Passed to. Moving to 5), the dynamic link mechanism of the present invention first searches the virtual address space with the name mark X when loading the program B. In other words, when X is found in the program B, the search is made with the name mark X. When the mark X is found, the common section length is compared. In the program A, the length of the mark X was 100A, but in the program B, X was defined as 300A. Therefore, the value of X updated by the program A can be directly copied to the X of the program B.

That is, if the lengths are different, a new area is newly acquired to the longer length of the area, and the contents are copied from the old area to the new area. In this example, since the length of the common section of the program B is already longer than the length of the common section of the program A, it can be copied as it is. Thus, the address of the new area, that is, the start address of the common section, is newly changed. Then, the head address of the common section is stored in the address constant area of the program A and the program B, that is, XCOM and YCOM. After this operation is completed, the dynamic link mechanism passes control to the program B. Since X is used in the program B as well, the contents of the common section area are changed and referred to when the program B is executed. The changed content is in the instruction below the CALL statement of program A,
Will be used.

[0025]

【The invention's effect】

As described above, according to the present invention, even in a case where load modules with a common section are mixed, a dynamic link is used in all cases in order to use a dynamic link without being conscious of its existence. A program execution environment and a program maintenance / management environment can be constructed. Therefore, the working set can be reduced to the minimum required at the time of execution, the disk capacity can be reduced to the minimum required when capturing a load module, and relinking is not required for maintenance and management. The maintenance method can be kept consistent, which greatly contributes to program development, construction of a program execution environment, and resource saving and simplification of procedures for program maintenance and management.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of the present invention.

FIG. 3 is an embodiment diagram of a procedure for accessing a common section.

FIG. 4 is an embodiment diagram of a program corresponding to a load module holding a common section according to the common section dynamic link method of the present invention.

[Explanation of symbols]

 1 ... Common section presence / absence identification means 2 ... Common section sharing control means 3 ... Common section erroneous length detection means 4 ... Common section access control means

Continuation of the front page (56) References JP-A-62-241031 (JP, A) JP-A-62-163148 (JP, A) JP-B-62-32497 (JP, B2) “FACOM OSIV / X8, Linkage Editor / Loader User's Guide 65 SP-3522-1 "p. 19-21, p. 76-77 (See the section on integration of common section.), Fujitsu Limited, December 1983

Claims (1)

(57) [Claims] In a dynamic link system for dynamically linking a plurality of load modules for which a common section has been declared, a second load for which a dynamic link has been requested from a first load module that has already been loaded. When loading a module, comparing and judging means for judging a length of a common section declared in the second load module and a length of an existing common section; If it is determined that the length of the common section declared in the load module is longer than the length of the existing common section, the length of the common section declared in the second load module is Obtaining a new area of equal length, copying the contents of the existing common section into the new area, The 該新 region as a new common section area, dynamic linking system, characterized in that it comprises an access control means for accessing each of the load modules that are declared common section, the.