Method and device for dynamically substituting C/C + + function in main program

Abstract

The invention provides a method and a device for dynamically substituting a C / C + + function in a main program. The method includes steps as follows: the main program is started, and a substitution program module used for inquiring and modifying a memory is loaded; the loaded substitution program module is initialized, so that the substitution program module is executed in advance of a main function in the main program; symbol table information of a function in the main program is stored in the memory; after the substitution program module receives a substitution instruction, the substitution program module determines a mapping address of a substituted function in the memory according to symbol table information corresponding to the substituted function; and the substituted function is substituted according to the mapping address. The method and the device can dynamically substitute and restore the function during operation of the program, the program is not required to be recompiled, time is saved, high efficiency is realized, and the infinite loop phenomenon when the substituted function is indirectly called inside a substitution function is avoided.

Description

technical field [0001] The invention relates to the technical field of computer science, in particular to a method and a device for dynamically replacing C / C++ functions in a main program. Background technique [0002] When debugging, mocking and testing C / C++ programs under Linux, function replacement is often required. Function replacement refers to using the replacement function to overwrite the replaced function. The existing technology for replacing C / C++ functions under Linux mainly completes the function replacement by setting the LD_PRELOAD environment variable and loading the shared library once when the program starts. During the loading process, if there is a function with the same name in the shared library, such as malloc, the corresponding system function malloc will be automatically replaced with the replacement function malloc in the shared library. [0003] Although the existing method can realize function replacement, it has the following disadvantages: ...

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Problems solved by technology

[0004] (1) The method of setting the LD_PRELOAD environment variable under Linux is to load it once when the program starts, so the shared library function cannot be dynamically replaced and restored when the program is running

Every time a function is replaced, it is necessary to reload the shared library and start the program, so the operation time is long and the replacement efficiency is low

[0005] (2) Since the replaced system function will be completely replaced, if the replaced system function is called indirectly inside the replacement function, it will cause the replacement function to call itself repeatedly, resulting in an infinite loop

[0006] (3) The method of setting the LD_PRELOAD environment variable can only load shared library functions, so the existing methods cannot replace non-shared library functions, such as user-defined functions, etc., so it is inconvenient for users to use

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