CODEWITHSUNDEEP
clinuxtddfile-descriptor
fadedbee
fadedbee

Reputation: 44739

Testing a C function which uses file descriptors

I am writing some functions which will be called with file descriptor arguments in production code.

During testing, how can 'inject' something which will let me confirm that the function makes the intended calls to lseek, write and so on?

Upvotes: 1

Views: 118

Answers (2)

philant
philant

Reputation: 35806

Since you're on Linux, you can simply define the functions you want to stub inside your test program. The linker will deem these functions as local, and ignore those that will be dynamically loaded.
I used this successfully on Linux and Solaris with gcc.

Make sure to store the parameters they are invoked with and not to put assertions inside the stub functions, this will make them more reusable.

Upvotes: 2

chrylis -cautiouslyoptimistic-
chrylis -cautiouslyoptimistic-

Reputation: 77177

Depending on your operating system, the best solution is likely to be writing a "shim" library that gets dynamically linked in and intercepts the calls to the standard functions you're looking for, reporting out-of-band to the test harness. The libtrash library is a good example of how this works, and the code is readable; it implements a "trash can" for Linux by intercepting (some) calls to unlink and instead moving the links to a trash-can directory.

Upvotes: 2

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